Search Results: "beh"

24 July 2016

Tom Marble: jai-gagne-le-tour-de-crosstown-2016

J'ai gagn le Tour de Crosstown 2016! Everyone knows that today the finish line for Le Tour de France was crossed on Les Champs- lys es in Paris... And if you haven't seen some of the videos I highly recommend checking out the onboard camera views and the landscapes! Quel beau pays I'm happy to let you know that today I won the Tour de Crosstown 2016 which is the cycling competition at Lifetime Crosstown inspired by and concurrent to Le Tour de France. There were about twenty cyclists competing to see who could earn the most points -- by attending cycling class bien s r. I earned the maillot jaune with 23 points and my next closest competitor had 16 points (with the peloton far behind). But that's just part of the story.

Tour de Crosstown 2016
For some time I've been coming to Life Time Fitness at Crosstown for yoga (in Josefina's class) and playing racquetball with my friend David. The cycling studio is right next to the racquetball courts and there's been a class on Saturday's at the same time we usually play. I told David that it looked like fun and he said, having tried it, that it is fun (and a big workout). In early June David got busy and then had an injury that has kept him off the court ever since. So one Saturday morning I decided to try cycling. I borrowed a heart rate monitor (but had no idea what it was for) and tried to bike along in my regular gym shorts, shoes and a t-shirt. Despite being a cycling newbie I was immediately captured by Alison's music and enthusiasm. She's dancing on her bike and you can't help but lock in the beat. Of course that's just after she tells you to dial up the resistance... and the sweat just pours out! I admit that workout hit me pretty hard, but I had to come back and try the 5:45 am Wednesday EDGE cycle class (gulp). Despite what sounds like a crazy impossible time to get out and on a bike it actually works out super well. This plan requires one to up-level one's organization and after the workout I can assure you that you're fully awake and charged for the day! Soon I invested in my own heart rate monitor. Then I realized it would work so much better if I had a metabolic assessment to tune my aerobic and anaerobic training zones. While I signed up for the assessment I decided to work with May as my personal trainer. In addition to helping me with my upper body (complementing the cycling) May is a nutritionist and has helped me dial in this critical facet of training. Even though I'm still working to tune my diet around my workouts, I've already learned a lot by using My Fitness Pal and, most importantly, I have a whole new attitude about food. Pour les curieux, la nutritioniste maison s'est absent e en France pendant le mois de juillet. Soon I would invest in bike shoes, jerseys and shorts and begin to push myself into the proper zones during workouts and fuel my body properly afterwords. All these changes have led to dramatic weight loss \o/ A few of you know that the past two years have involved a lot of personal hardship. Upon reflection I have come to appreciate that things in my life that I can actually control are a massive opportunity. I decided that fixing my exercise and nutrition were the opportunities I want to focus on. A note for for my Debian friends... I'm sorry to have missed you in Cape Town, but I hope to join you in Montr al next year. So when the Tour de Crosstown started in July I decided this was the time for me to get serious. I want to thank all the instructors for the great workouts (and for all the calories I've left on the bike): Alison, Kristine, Olivia, Tasha, and Caroline! The result of my lifestyle changes are hard to describe.. I feel an amazing amount of energy every day. The impact of prior back injury is now almost non-existent. And what range of motion I hadn't recovered from the previous summer's being "washing machined" by a 3 meter wave while body surfing at the beach in Hossegor is now fully working. Now I'm thinking it's time to treat myself to a new bike :) I'm looking at large touring frames and am currently thinking of the Surly Disc Trucker. In terms of bike shops I've had a good experience with One on One and Grand Performance has come highly recommended. If anyone has suggestions for bikes, bike features, or good shops please let me know! I would encourage everyone here in Minneapolis to join me as guest for a Wed morning 5:45am EDGE cycle class. I'm betting you'll have as much fun as a I do.. and I guarantee you will sweat! The challenge in waking up will pay off handsomely in making you energized for the whole day. Let's bike allons-y!

Russ Allbery: Review: The Run of His Life

Review: The Run of His Life, by Jeffrey Toobin
Publisher: Random House
Copyright: 1996, 1997
Printing: 2015
ISBN: 0-307-82916-2
Format: Kindle
Pages: 498
The O.J. Simpson trial needs little introduction to anyone who lived through it in the United States, but a brief summary for those who didn't. O.J. Simpson is a Hall of Fame football player and one of the best running backs to ever play the game. He's also black, which is very relevant much of what later happened. After he retired from professional play, he became a television football commentator and a spokesperson for various companies (particularly Hertz, a car rental business). In 1994, he was arrested for the murder of two people: his ex-wife, Nicole Brown Simpson, and Ron Goldman (a friend of Nicole's). The arrest happened after a bizarre low-speed police chase across Los Angeles in a white Bronco that was broadcast live on network television. The media turned the resulting criminal trial into a reality TV show, with live cable television broadcasts of all of the court proceedings. After nearly a full year of trial (with the jury sequestered for nine months more on that later), a mostly black jury returned a verdict of not guilty after a mere four hours of deliberation. Following the criminal trial, in an extremely unusual legal proceeding, Simpson was found civilly liable for Ron Goldman's death in a lawsuit brought by his family. Bizarre events surrounding the case continued long afterwards. A book titled If I Did It (with "if" in very tiny letters on the cover) was published, ghost-written but allegedly with Simpson's input and cooperation, and was widely considered a confession. Another legal judgment let the Goldman family get all the profits from that book's publication. In an unrelated (but also bizarre) incident in Las Vegas, Simpson was later arrested for kidnapping and armed robbery and is currently in prison until at least 2017. It is almost impossible to have lived through the O.J. Simpson trial in the United States and not have formed some opinion on it. I was in college and without a TV set at the time, and even I watched some of the live trial coverage. Reactions to the trial were extremely racially polarized, as you might have guessed. A lot of black people believed at the time that Simpson was innocent (probably fewer now, given subsequent events). A lot of white people thought he was obviously guilty and was let off by a black jury for racial reasons. My personal opinion, prior to reading this book, was a common "third way" among white liberals: Simpson almost certainly committed the murders, but the racist Los Angeles police department decided to frame him for a crime that he did commit by trying to make the evidence stronger. That's a legitimate reason in the US justice system for finding someone innocent: the state has an obligation to follow correct procedure and treat the defendant fairly in order to get a conviction. I have a strong bias towards trusting juries; frequently, it seems that the media second-guesses the outcome of a case that makes perfect sense as soon as you see all the information the jury had (or didn't have). Toobin's book changed my mind. Perhaps because I wasn't watching all of the coverage, I was greatly underestimating the level of incompetence and bad decision-making by everyone involved: the prosecution, the defense, the police, the jury, and the judge. This court case was a disaster from start to finish; no one involved comes away looking good. Simpson was clearly guilty given the evidence presented, but the case was so badly mishandled that it gave the jury room to reach the wrong verdict. (It's telling that, in the far better managed subsequent civil case, the jury had no trouble reaching a guilty verdict.) The Run of His Life is a very detailed examination of the entire Simpson case, from the night of the murder through the end of the trial and (in an epilogue) the civil case. Toobin was himself involved in the media firestorm, breaking some early news of the defense's decision to focus on race in The New Yorker and then involved throughout the trial as a legal analyst, and he makes it clear when he becomes part of the story. But despite that, this book felt objective to me. There are tons of direct quotes, lots of clear description of the evidence, underlying interviews with many of the people involved to source statements in the book, and a comprehensive approach to the facts. I think Toobin is a bit baffled by the black reaction to the case, and that felt like a gap in the comprehensiveness and the one place where he might be accused of falling back on stereotypes and easy judgments. But other than hole, Toobin applies his criticism even-handedly and devastatingly to all parties. I won't go into all the details of how Toobin changed my mind. It was a cumulative effect across the whole book, and if you're curious, I do recommend reading it. A lot was the detailed discussion of the forensic evidence, which was undermined for the jury at trial but looks very solid outside the hothouse of the case. But there is one critical piece that I would hope would be handled differently today, twenty years later, than it was by the prosecutors in that case: Simpson's history of domestic violence against Nicole. With what we now know about patterns of domestic abuse, the escalation to murder looks entirely unsurprising. And that history of domestic abuse was exceedingly well-documented: multiple external witnesses, police reports, and one actual prior conviction for spousal abuse (for which Simpson did "community service" that was basically a joke). The prosecution did a very poor job of establishing this history and the jury discounted it. That was a huge mistake by both parties. I'll mention one other critical collection of facts that Toobin explains well and that contradicted my previous impression of the case: the relationship between Simpson and the police. Today, in the era of Black Lives Matter, the routine abuse of black Americans by the police is more widely known. At the time of the murders, it was less recognized among white Americans, although black Americans certainly knew about it. But even in 1994, the Los Angeles police department was notorious as one of the most corrupt and racist big-city police departments in the United States. This is the police department that beat Rodney King. Mark Fuhrman, one of the police officers involved in the case (although not that significantly, despite his role at the trial), was clearly racist and had no business being a police officer. It was therefore entirely believable that these people would have decided to frame a black man for a murder he actually committed. What Toobin argues, quite persuasively and with quite a lot of evidence, is that this analysis may make sense given the racial tensions in Los Angeles but ignores another critical characteristic of Los Angeles politics, namely a deference to celebrity. Prior to this trial, O.J. Simpson largely followed the path of many black athletes who become broadly popular in white America: underplaying race and focusing on his personal celebrity and connections. (Toobin records a quote from Simpson earlier in his life that perfectly captures this approach: "I'm not black, I'm O.J.") Simpson spent more time with white businessmen than the black inhabitants of central Los Angeles. And, more to the point, the police treated him as a celebrity, not as a black man. Toobin takes some time to chronicle the remarkable history of deference and familiarity that the police showed Simpson. He regularly invited police officers to his house for parties. The police had a long history of largely ignoring or downplaying his abuse of his wife, including not arresting him in situations that clearly seemed to call for that, showing a remarkable amount of deference to his side of the story, not pursuing clear violations of the court judgment after his one conviction for spousal abuse, and never showing much inclination to believe or protect Nicole. Even on the night of the murder, they started following a standard playbook for giving a celebrity advance warning of investigations that might involve them before the news media found out about them. It seems clear, given the evidence that Toobin collected, that the racist Los Angeles police didn't focus that animus at Simpson, a wealthy celebrity living in Brentwood. He wasn't a black man in their eyes; he was a rich Hall of Fame football player and a friend. This obviously raises the question of how the jury could return an innocent verdict. Toobin provides plenty of material to analyze that question from multiple angles in his detailed account of the case, but I can tell you my conclusion: Judge Lance Ito did a horrifically incompetent job of managing the case. He let the lawyers wander all over the case, interacted bizarrely with the media coverage (and was part of letting the media turn it into a daytime drama), was not crisp or clear about his standards of evidence and admissibility, and, perhaps worst of all, let the case meander on at incredible length. With a fully sequestered jury allowed only brief conjugal visits and no media contact (not even bookstore shopping!). Quite a lot of anger was focused on the jury after the acquittal, and I do think they reached the wrong conclusion and had all the information they would have needed to reach the correct one. But Toobin touches on something that I think would be very hard to comprehend without having lived through it. The jury and alternate pool essentially lived in prison for nine months, with guards and very strict rules about contact with the outside world, in a country where compensation for jury duty is almost nonexistent. There were a lot of other factors behind their decision, including racial tensions and the sheer pressure from judging a celebrity case about which everyone has an opinion, but I think it's nearly impossible to underestimate the psychological tension and stress from being locked up with random other people under armed guard for three quarters of a year. It's hard for jury members to do an exhaustive and careful deliberation in a typical trial that takes a week and doesn't involve sequestration. People want to get back to their lives and families. I can only imagine the state I would be in after nine months of this, or how poor psychological shape I would be in to make a careful and considered decision. Similarly, for those who condemned the jury for profiting via books and media appearances after the trial, the current compensation for jurors is $15 per day (not hour). I believe at the time it was around $5 per day. There are a few employers who will pay full salary for the entire jury service, but only a few; many cap the length at a few weeks, and some employers treat all jury duty as unpaid leave. The only legal requirement for employers in the United States is that employees that serve on a jury have their job held for them to return to, but compensation is pathetic, not tied to minimum wage, and employers do not have to supplement it. I'm much less inclined to blame the jurors than the system that badly mistreated them. As you can probably tell from the length of this review, I found The Run of His Life fascinating. If I had followed the whole saga more closely at the time, this may have been old material, but I think my vague impressions and patchwork of assumptions were more typical than not among people who were around for the trial but didn't invest a lot of effort into following it. If you are like me, and you have any interest in the case or the details of how the US criminal justice system works, this is a fascinating case study, and Toobin does a great job with it. Recommended. Rating: 8 out of 10

22 July 2016

Norbert Preining: Yukio Mishima The Temple of the Golden Pavilion

A masterpiece of modern Japanese literature: Yukio Mishima ( ) The Temple of the Golden Pavilion ( ). The fictional story about the very real arson attack that destroyed the Golden Pavilion in 1950.
mishima-golden-temple A bit different treatise on beauty and ugliness!
How shall I put it? Beauty yes, beauty is like a decayed tooth. It rubs against one s tongue, it hangs there, hurting one, insisting on its own existence, finally [ ] the tooth extracted. Then, as one looks at the small, dirty, brown, blood-stained tooth lying in one s hand, one s thoughts are likely to be as follows: Is this it?
Mizoguchi, a stutterer, is from young years on taken by a near mystical imagination of the Golden Pavilion, influence by his father who considers it the most beautiful object in the world. After his father s death he moves to Kyoto and becomes acolyte in the temple. He develops a friendship with Kashiwagi, who uses his clubfeet to make women feel sorry for him and make them fall in love with his clubfeet, as he puts it. Kashiwagi also puts Mizoguchi onto the first tracks of amorous experiences, but Mizoguchi invariably turns out to be impotent but not due to his stuttering, but due to the image of the Golden Pavilion appearing in the essential moment and destroying every chance.
Yes, this was really the coast of the Sea of Japan! Here was the source of all my unhappiness, of all my gloomy thoughts, the origin of all my ugliness and all my strength. It was a wild sea.
Mizoguchi is getting more and more mentally about his relation with the head monk, neglects his studies, and after a stark reprimand he escapes to the north coast, from where he is brought back by police to the temple. He decides to burn down the Golden Pavilion, which has taken more and more command of his thinking and doing. He carries out the deed with the aim to burn himself in the top floor, but escapes in the last second to retreat into the hills to watch the spectacle.
Closely based on the true story of the arsonist of the Golden Pavilion, whom Mishima even visited in prison, the book is a treatise about beauty and ugly.
At his trial he [the real arsonist] said: I hate myself, my evil, ugly, stammering self. Yet he also said that he did not in any way regret having burned down the Kinkakuji.
Nancy Wilson Ross in the preface
Mishima is master in showing these two extremes by contrasting the refined qualities of Japanese culture flower arrangement, playing the shakuhachi, with immediate outburst of contrasting behavior: cold and brutal recklessness. Take for example the scene were Kashiwagi is arranging flowers, stolen by Mizoguchi from the temple grounds, while Mizoguchi is playing the flute. They also discuss koans and various interpretations. Enters the Ikebana teacher, and mistress of Kashiwagi. She congratulates Kashiwagi to his excellent arrangement, which he answers coldly by quitting their relationship, both as teacher as well as mistress, and telling her not to see him again in a formal style. She, still ceremonially kneeling, suddenly destroys the flower arrangement, only to be beaten and thrown out by Kashiwagi. And the beauty and harmony has turned to ugliness and hate in seconds. Beauty and Ugliness, two sides of the same medal, or inherently the same, because it is only up to the point of view. Mishima ingeniously plays with this duality, and leads us through the slow and painful development of Mizoguchi to the bitter end, which finally gives him freedom, freedom from the force of beauty. Sometimes seeing how our society is obsessed with beauty I cannot get rid of the feeling that there are far more Mizoguchis at heart.

21 July 2016

Reproducible builds folks: Reproducible builds: week 62 in Stretch cycle

What happened in the Reproducible Builds effort between June 26th and July 2nd 2016: Read on to find out why we're lagging some weeks behind ! GSoC and Outreachy updates Toolchain fixes With the doxygen upload we are now down to only 2 modified packages in our repository: dpkg and rdfind. Weekly reports delay and the future of statistics To catch up with our backlog of weekly reports we have decided to skip some of the statistics for this week. We might publish them in a future report, or we might switch to a format where we summarize them more (and which we can create (even) more automatically), we'll see. We are doing these weekly statistics because we believe it's appropriate and useful to credit people's work and make it more visible. What do you think? We would love to hear your thoughts on this matter! Do you read these statistics? Somewhat? Actually, thanks to the power of notmuch, Holger came up with what you can see below, so what's missing for this week are the uploads fixing irreprodubilities. Which we really would like to show for the reasons stated above and because we really really need these uploads to happen ;-) But then we also like to confirm the bugs are really gone, which (atm) requires manual checking, and to look for the words "reproducible" and "deterministic" (and spelling variations) in debian/changelogs of all uploads, to spot reproducible work not tracked via the BTS. And we still need to catch up on the backlog of weekly reports. Bugs submitted with reproducible usertags It seems DebCamp in Cape Town was hugely successful and made some people get a lot of work done: 61 bugs have been filed with reproducible builds usertags and 60 of them had patches: Package reviews 437 new reviews have been added (though most of them were just linking the bug, "only" 56 new issues in packages were found), an unknown number has been been updated and 60 have been removed in this week, adding to our knowledge about identified issues. 4 new issue types have been found: Weekly QA work 98 FTBFS bugs have been reported by Chris Lamb and Santiago Vila. diffoscope development strip-nondeterminism development tests.reproducible-builds.org Misc. This week's edition was written by Mattia Rizzolo, Reiner Herrmann, Ceridwen and Holger Levsen and reviewed by a bunch of Reproducible builds folks on IRC.

20 July 2016

Daniel Stender: Theano in Debian: maintenance, BLAS and CUDA

I'm glad to announce that we have the current release of Theano (0.8.2) in Debian unstable now, it's on its way into the testing branch and the Debian derivatives, heading for Debian 9. The Debian package is maintained in behalf of the Debian Science Team. We have a binary package with the modules in the Python 2.7 import path (python-theano), if you want or need to stick to that branch a little longer (as a matter of fact, in the current popcon stats it's the most installed package), and a package running on the default Python 3 version (python3-theano). The comprehensive documentation is available for offline usage in another binary package (theano-doc). Although Theano builds its extensions on run time and therefore all binary packages contain the same code, the source package generates arch specific packages1 for the reason that the exhaustive test suite could run over all the architectures to detect if there are problems somewhere (#824116). what's this? In a nutshell, Theano is a computer algebra system (CAS) and expression compiler, which is implemented in Python as a library. It is named after a Classical Greek female mathematician and it's developed at the LISA lab (located at MILA, the Montreal Institute for Learning Algorithms) at the Universit de Montr al. Theano tightly integrates multi-dimensional arrays (N-dimensional, ND-array) from NumPy (numpy.ndarray), which are broadly used in Scientific Python for the representation of numeric data. It features a declarative Python based language with symbolic operations for the functional definition of mathematical expressions, which allows to create functions that compute values for them. Internally the expressions are represented as directed graphs with nodes for variables and operations. The internal compiler then optimizes those graphs for stability and speed and then generates high-performance native machine code to evaluate resp. compute these mathematical expressions2. One of the main features of Theano is that it's capable to compute also on GPU processors (graphical processor unit), like on custom graphic cards (e.g. the developers are using a GeForce GTX Titan X for benchmarks). Today's GPUs became very powerful parallel floating point devices which can be employed also for scientific computations instead of 3D video games3. The acronym "GPGPU" (general purpose graphical processor unit) refers to special cards like NVIDIA's Tesla4, which could be used alike (more on that below). Thus, Theano is a high-performance number cruncher with an own computing engine which could be used for large-scale scientific computations. If you haven't came across Theano as a Pythonistic professional mathematician, it's also one of the most prevalent frameworks for implementing deep learning applications (training multi-layered, "deep" artificial neural networks, DNN) around5, and has been developed with a focus on machine learning from the ground up. There are several higher level user interfaces build in the top of Theano (for DNN, Keras, Lasagne, Blocks, and others, or for Python probalistic programming, PyMC3). I'll seek for some of them also becoming available in Debian, too. helper scripts Both binary packages ship three convenience scripts, theano-cache, theano-test, and theano-nose. Instead of them being copied into /usr/bin, which would result into a binaries-have-conflict violation, the scripts are to be found in /usr/share/python-theano (python3-theano respectively), so that both module packages of Theano can be installed at the same time. The scripts could be run directly from these folders, e.g. do $ python /usr/share/python-theano/theano-nose to achieve that. If you're going to heavy use them, you could add the directory of the flavour you prefer (Python 2 or Python 3) to the $PATH environment variable manually by either typing e.g. $ export PATH=/usr/share/python-theano:$PATH on the prompt, or save that line into ~/.bashrc. Manpages aren't available for these little helper scripts6, but you could always get info on what they do and which arguments they accept by invoking them with the -h (for theano-nose) resp. help flag (for theano-cache). running the tests On some occasions you might want to run the testsuite of the installed library, like to check over if everything runs fine on your GPU hardware. There are two different ways to run the tests (anyway you need to have python ,3 -nose installed). One is, you could launch the test suite by doing $ python -c 'import theano; theano.test() (or the same with python3 to test the other flavour), that's the same what the helper script theano-test does. However, by doing it that way some particular tests might fail by raising errors also for the group of known failures. Known failures are excluded from being errors if you run the tests by theano-nose, which is a wrapper around nosetests, so this might be always the better choice. You can run this convenience script with the option --theano on the installed library, or from the source package root, which you could pull by $ sudo apt-get source theano (there you have also the option to use bin/theano-nose). The script accept options for nosetests, so you might run it with -v to increase verbosity. For the tests the configuration switch config.device must be set to cpu. This will also include the GPU tests when a proper accessible device is detected, so that's a little misleading in the sense of it doesn't mean "run everything on the CPU". You're on the safe side if you run it always like this: $ THEANO_FLAGS=device=cpu theano-nose, if you've set config.device to gpu in your ~/.theanorc. Depending on the available hardware and the used BLAS implementation (see below) it could take quite a long time to run the whole test suite through, on the Core-i5 in my laptop that takes around an hour even excluded the GPU related tests (which perform pretty fast, though). Theano features a couple of switches to manipulate the default configuration for optimization and compilation. There is a rivalry between optimization and compilation costs against performance of the test suite, and it turned out the test suite performs a quicker with lesser graph optimization. There are two different switches available to control config.optimizer, the fast_run toggles maximal optimization, while fast_compile runs only a minimal set of graph optimization features. These settings are used by the general mode switches for config.mode, which is either FAST_RUN by default, or FAST_COMPILE. The default mode FAST_RUN (optimizer=fast_run, linker=cvm) needs around 72 minutes on my lower mid-level machine (on un-optimized BLAS). To set mode=FAST_COMPILE (optimizer=fast_compile, linker=py) brings some boost for the performance of the test suite because it runs the whole suite in 46 minutes. The downside of that is that C code compilation is disabled in this mode by using the linker py, and also the GPU related tests are not included. I've played around with using the optimizer fast_compile with some of the other linkers (c py and cvm, and their versions without garbage collection) as alternative to FAST_COMPILE with minimal optimization but also machine code compilation incl. GPU testing. But to my experience, fast_compile without another than the linker py results in some new errors and failures of some tests on amd64, and this might the case also on other architectures, too. By the way, another useful feature is DebugMode for config.mode, which verifies the correctness of all optimizations and compares the C to Python results. If you want to have detailed info on the configuration settings of Theano, do $ python -c 'import theano; print theano.config' less, and check out the chapter config in the library documentation in the documentation. cache maintenance Theano isn't a JIT (just-in-time) compiler like Numba, which generates native machine code in the memory and executes it immediately, but it saves the generated native machine code into compiledirs. The reason for doing it that way is quite practical like the docs explain, the persistent cache on disk makes it possible to avoid generating code for the same operation, and to avoid compiling again when different operations generate the same code. The compiledirs by default are located within $(HOME)/.theano/. After some time the folder becomes quite large, and might look something like this:
$ ls ~/.theano
compiledir_Linux-4.5--amd64-x86_64-with-debian-stretch-sid--2.7.11+-64
compiledir_Linux-4.5--amd64-x86_64-with-debian-stretch-sid--2.7.12-64
compiledir_Linux-4.5--amd64-x86_64-with-debian-stretch-sid--2.7.12rc1-64
compiledir_Linux-4.5--amd64-x86_64-with-debian-stretch-sid--3.5.1+-64
compiledir_Linux-4.5--amd64-x86_64-with-debian-stretch-sid--3.5.2-64
compiledir_Linux-4.5--amd64-x86_64-with-debian-stretch-sid--3.5.2rc1-64
If the used Python version changed like in this example you might to want to purge obsolete cache. For working with the cache resp. the compiledirs, the helper theano-cache comes in handy. If you invoke it without any arguments the current cache location is put out like ~/.theano/compiledir_Linux-4.5--amd64-x86_64-with-debian-stretch-sid--2.7.12-64 (the script is run from /usr/share/python-theano). So, the compiledirs for the old Python versions in this example (11+ and 12rc1) can be removed to free the space they occupy. All compiledirs resp. cache directories meaning the whole cache could be erased by $ theano-cache basecompiledir purge, the effect is the same as by performing $ rm -rf ~/.theano. You might want to do that e.g. if you're using different hardware, like when you got yourself another graphics card. Or habitual from time to time when the compiledirs fill up so much that it slows down processing with the harddisk being very busy all the time, if you don't have an SSD drive available. For example, the disk space of build chroots carrying (mainly) the tests completely compiled through on default Python 2 and Python 3 consumes around 1.3 GB (see here). BLAS implementations Theano needs a level 3 implementation of BLAS (Basic Linear Algebra Subprograms) for operations between vectors (one-dimensional mathematical objects) and matrices (two-dimensional objects) carried out on the CPU. NumPy is already build on BLAS and pulls the standard implementation (libblas3, soure package: lapack), but Theano links directly to it instead of using NumPy as intermediate layer to reduce the computational overhead. For this, Theano needs development headers and the binary packages pull libblas-dev by default, if any other development package of another BLAS implementation (like OpenBLAS or ATLAS) isn't already installed, or pulled with them (providing the virtual package libblas.so). The linker flags could be manipulated directly through the configuration switch config.blas.ldflags, which is by default set to -L/usr/lib -lblas -lblas. By the way, if you set it to an empty value, Theano falls back to using BLAS through NumPy, if you want to have that for some reason. On Debian, there is a very convenient way to switch between BLAS implementations by the alternatives mechanism. If you have several alternative implementations installed at the same time, you can switch from one to another easily by just doing:
$ sudo update-alternatives --config libblas.so
There are 3 choices for the alternative libblas.so (providing /usr/lib/libblas.so).
  Selection    Path                                  Priority   Status
------------------------------------------------------------
* 0            /usr/lib/openblas-base/libblas.so      40        auto mode
  1            /usr/lib/atlas-base/atlas/libblas.so   35        manual mode
  2            /usr/lib/libblas/libblas.so            10        manual mode
  3            /usr/lib/openblas-base/libblas.so      40        manual mode
Press <enter> to keep the current choice[*], or type selection number:
The implementations are performing differently on different hardware, so you might want to take the time to compare which one does it best on your processor (the other packages are libatlas-base-dev and libopenblas-dev), and choose that to optimize your system. If you want to squeeze out all which is in there for carrying out Theano's computations on the CPU, another option is to compile an optimized version of a BLAS library especially for your processor. I'm going to write another blog posting on this issue. The binary packages of Theano ship the script check_blas.py to check over how well a BLAS implementation performs with it, and if everything works right. That script is located in the misc subfolder of the library, you could locate it by doing $ dpkg -L python-theano grep check_blas (or for the package python3-theano accordingly), and run it with the Python interpreter. By default the scripts puts out a lot of info like a huge perfomance comparison reference table, the current setting of blas.ldflags, the compiledir, the setting of floatX, OS information, the GCC version, the current NumPy config towards BLAS, NumPy location and version, if Theano linked directly or has used the NumPy binding, and finally and most important, the execution time. If just the execution time for quick perfomance comparisons is needed this script could be invoked with -q. Theano on CUDA The function compiler of Theano works with alternative backends to carry out the computations, like the ones for graphics cards. Currently, there are two different backends for GPU processing available, one docks onto NVIDIA's CUDA (Compute Unified Device Architecture) technology7, and another one for libgpuarray, which is also developed by the Theano developers in parallel. The libgpuarray library is an interesting alternative for Theano, it's a GPU tensor (multi-dimensional mathematical object) array written in C with Python bindings based on Cython, which has the advantage of running also on OpenCL8. OpenCL, unlike CUDA9, is full free software, vendor neutral and overcomes the limitation of the CUDA toolkit being only available for amd64 and the ppc64el port (see here). I've opened an ITP on libgpuarray and we'll see if and how this works out. Another reason for it would be great to have it available is that it looks like CUDA currently runs into problems with GCC 610. More on that, soon. Here's a litle checklist for setting up your CUDA device so that you don't have to experience something like this:
$ THEANO_FLAGS=device=gpu,floatX=float32 python ./cat_dog_classifier.py 
WARNING (theano.sandbox.cuda): CUDA is installed, but device gpu is not available (error: Unable to get the number of gpus available: no CUDA-capable device is detected)
hardware check For running Theano on CUDA you need an NVIDIA graphics card which is capable of doing that. You can recheck if your device is supported by CUDA here. When the hardware isn't too old (CUDA support started with GeForce 8 and Quadro X series) or too strange I think it isn't working only in exceptional cases. You can check your model and if the device is present in the system on the bare hardware level by doing this:
$ lspci   grep -i nvidia
04:00.0 3D controller: NVIDIA Corporation GM108M [GeForce 940M] (rev a2)
If a line like this doesn't get returned, your device most probably is broken, or not properly connected (ouch). If rev ff appears at the end of the line that means the device is off meaning powered down. This might be happening if you have a laptop with Optimus graphics hardware, and the related drivers have switched off the unoccupied device to safe energy11. kernel module Running CUDA applications requires the proprietary NVIDIA driver kernel module to be loaded into the kernel and working. If you haven't already installed it for another purpose, the NVIDIA driver and the CUDA toolkit are both in the non-free section of the Debian archive, which is not enabled by default. To get non-free packages you have to add non-free (and it's better to do so, also contrib) to your package source in /etc/apt/sources.list, which might then look like this:
deb http://httpredir.debian.org/debian/ testing main contrib non-free
After doing that, perform $ apt-cache update to update the package lists, and there you go with the non-free packages. The headers of the running kernel are needed to compile modules, you can get them together with the NVIDIA kernel module package by running:
$ sudo apt-get install linux-headers-$(uname -r) nvidia-kernel-dkms build-essential
DKMS will then build the NVIDIA module for the kernel and does some other things on the system. When the installation has finished, it's generally advised to reboot the system completely. troubleshooting If you have problems with the CUDA device, it's advised to verify if the following things concerning the NVIDIA driver resp. kernel module are in order: blacklist nouveau Check if the default Nouveau kernel module driver (which blocks the NVIDIA module) for some reason still gets loaded by doing $ lsmod grep nouveau. If nothing gets returned, that's right. If it's still in the kernel, just add blacklist nouveau to /etc/modprobe.d/blacklist.conf, and update the booting ramdisk with sudo update-initramfs -u afterwards. Then reboot once more, this shouldn't be the case then anymore. rebuild kernel module To fix it when the module haven't been properly compiled for some reason you could trigger a rebuild of the NVIDIA kernel module with $ sudo dpkg-reconfigure nvidia-kernel-dkms. When you're about to send your hardware in to repair because everything looks all right but the device just isn't working, that really could help (own experience). After the rebuild of the module or modules (if you have a few kernel packages installed) has completed, you could recheck if the module really is available by running:
$ sudo modinfo nvidia-current
filename:       /lib/modules/4.4.0-1-amd64/updates/dkms/nvidia-current.ko
alias:          char-major-195-*
version:        352.79
supported:      external
license:        NVIDIA
alias:          pci:v000010DEd00000E00sv*sd*bc04sc80i00*
alias:          pci:v000010DEd*sv*sd*bc03sc02i00*
alias:          pci:v000010DEd*sv*sd*bc03sc00i00*
depends:        drm
vermagic:       4.4.0-1-amd64 SMP mod_unload modversions 
parm:           NVreg_Mobile:int
It should be something similiar to this when everything is all right. reload kernel module When there are problems with the GPU, maybe the kernel module isn't properly loaded. You could recheck if the module has been properly loaded by doing
$ lsmod   grep nvidia
nvidia_uvm             73728  0
nvidia               8540160  1 nvidia_uvm
drm                   356352  7 i915,drm_kms_helper,nvidia
The kernel module could be loaded resp. reloaded with $ sudo nvidia-modprobe (that tool is from the package nvidia-modprobe). unsupported graphics card Be sure that you graphics cards is supported by the current driver kernel module. If you have bought new hardware, that's quite possible to come out being a problem. You can get the version of the current NVIDIA driver with:
$ cat /proc/driver/nvidia/version 
NVRM version: NVIDIA UNIX x86_64 Kernel Module 352.79  Wed Jan 13 16:17:53 PST 2016
GCC version:  gcc version 5.3.1 20160528 (Debian 5.3.1-21)
Then, google the version number like nvidia 352.79, this should get you onto an official driver download page like this. There, check for what's to be found under "Supported Products". I you're stuck with that there are two options, to wait until the driver in Debian got updated, or replace it with the latest driver package from NVIDIA. That's possible to do, but something more for experienced users. occupied graphics card The CUDA driver cannot work while the graphical interface is busy like by processing the graphical display of your X.Org server. Which kernel driver actually is used to process the desktop could be examined by this command:12
$ grep '(II).*([0-9]):' /var/log/Xorg.0.log
[    37.700] (II) intel(0): Using Kernel Mode Setting driver: i915, version 1.6.0 20150522
[    37.700] (II) intel(0): SNA compiled: xserver-xorg-video-intel 2:2.99.917-2 (Vincent Cheng <vcheng@debian.org>)
 ... 
[    39.808] (II) intel(0): switch to mode 1920x1080@60.0 on eDP1 using pipe 0, position (0, 0), rotation normal, reflection none
[    39.810] (II) intel(0): Setting screen physical size to 508 x 285
[    67.576] (II) intel(0): EDID vendor "CMN", prod id 5941
[    67.576] (II) intel(0): Printing DDC gathered Modelines:
[    67.576] (II) intel(0): Modeline "1920x1080"x0.0  152.84  1920 1968 2000 2250  1080 1083 1088 1132 -hsync -vsync (67.9 kHz eP)
This example shows that the rendering of the desktop is performed by the graphical device of the Intel CPU, which is just like it's needed for running CUDA applications on your NVIDIA graphics card, if you don't have another one. nvidia-cuda-toolkit With the Debian package of the CUDA toolkit everything pretty much runs out of the box for Theano. Just install it with apt-get, and you're ready to go, the CUDA backend is the default one. Pycuda is also a suggested dependency of the binary packages, it could be pulled together with the CUDA toolkit. The up-to-date CUDA release 7.5 is of course available, with that you have Maxwell architecture support so that you can run Theano on e.g. a GeForce GTX Titan X with 6,2 TFLOPS on single precision13 at an affordable price. CUDA 814 is around the corner with support for the new Pascal architecture15. Like the GeForce GTX 1080 high-end gaming graphics card already has 8,23 TFLOPS16. When it comes to professional GPGPU hardware like the Tesla P100 there is much more computational power available, scalable by multiplication of cores resp. cards up to genuine little supercomputers which fit on a desk, like the DGX-117. Theano can use multiple GPUs for calculations to work with highly scaled hardware, I'll write another blog post on this issue. Theano on the GPU It's not difficult to run Theano on the GPU. Only single precision floating point numbers (float32) are supported on the GPU, but that is sufficient for deep learning applications. Theano uses double precision floats (float64) by default, so you have to set the configuration variable config.floatX to float32, like written on above, either with the THEANO_FLAGS environment variable or better in your .theanorc file, if you're going to use the GPU a lot. Switching to the GPU actually happens with the config.device configuration variable, which must be set to either gpu or gpu0, gpu1 etc., to choose a particular one if multiple devices are available. Here's is a little test script check1.py, it's taken from the docs and slightly altered. You can run that script either with python or python3 (there was a single test failure on the Python 3 package, so the Python 2 library might be a little more stable currently). For comparison, here's an example on how it perfoms on my hardware, one time on the CPU, one more time on the GPU:
$ THEANO_FLAGS=floatX=float32 python ./check1.py 
[Elemwise exp,no_inplace (<TensorType(float32, vector)>)]
Looping 1000 times took 4.481719 seconds
Result is [ 1.23178029  1.61879337  1.52278066 ...,  2.20771813  2.29967761
  1.62323284]
Used the cpu
$ THEANO_FLAGS=floatX=float32,device=gpu python ./check1.py 
Using gpu device 0: GeForce 940M (CNMeM is disabled, cuDNN not available)
[GpuElemwise exp,no_inplace (<CudaNdarrayType(float32, vector)>), HostFromGpu(GpuElemwise exp,no_inplace .0)]
Looping 1000 times took 1.164906 seconds
Result is [ 1.23178029  1.61879349  1.52278066 ...,  2.20771813  2.29967761
  1.62323296]
Used the gpu
If you got a result like this you're ready to go with Theano on Debian, training computer vision classifiers or whatever you want to do with it. I'll write more on for what Theano could be used, soon.

  1. Some ports are disabled because they are currently not supported by Theano. There are NotImplementedErrors and other errors in the tests on the numpy.ndarray object being not aligned. The developers commented on that, see here. And on some ports the build flags -m32 resp. -m64 of Theano aren't supported by g++, the build flags can't be manipulated easily.
  2. Theano Development Team: "Theano: a Python framework for fast computation of mathematical expressions"
  3. Marc Couture: "Today's high-powered GPUs: strong for graphics and for maths". In: RTC magazine June 2015, pp. 22 25
  4. Ogier Maitre: "Understanding NVIDIA GPGPU hardware". In: Tsutsui/Collet (eds.): Massively parallel evolutionary computation on GPGPUs. Berlin, Heidelberg: Springer 2013, pp. 15-34
  5. Geoffrey French: "Deep learing tutorial: advanved techniques". PyData London 2016 presentation
  6. Like the description of the Lintian tag binary-without-manpage says, that's not needed for them being in /usr/share.
  7. Tom. R. Halfhill: "Parallel processing with CUDA: Nvidia's high-performance computing platform uses massive multithreading". In: Microprocessor Report January 28, 2008
  8. Faber et.al: "Parallelwelten: GPU-Programmierung mit OpenCL". In: C't 26/2014, pp. 160-165
  9. For comparison, see: Valentine Sinitsyn: "Feel the taste of GPU programming". In: Linux Voice February 2015, pp. 106-109
  10. https://lists.debian.org/debian-devel/2016/07/msg00004.html
  11. If Optimus (hybrid) graphics hardware is present (like commonly today on PC laptops), Debian launches the X-server on the graphics processing unit of the CPU, which is ideal for CUDA. The problem with Optimus actually is the graphics processing on the dedicated GPU. If you are using Bumblebee, the Python interpreter which you want to run Theano on has be to be started with the launcher primusrun, because Bumblebee powers the GPU down with the tool bbswitch every time it isn't used, and I think also the kernel module of the driver is dynamically loaded.
  12. Thorsten Leemhuis: "Treiberreviere. Probleme mit Grafiktreibern f r Linux l sen": In: C't Nr.2/2013, pp. 156-161
  13. Martin Fischer: "4K-Rakete: Die schnellste Single-GPU-Grafikkarte der Welt". In C't 13/2015, pp. 60-61
  14. http://www.heise.de/developer/meldung/Nvidia-CUDA-8-bringt-Optimierungen-fuer-die-Pascal-Architektur-3164254.html
  15. Martin Fischer: "All In: Nvidia enth llt die GPU-Architektur 'Pascal'". In: C't 9/2016, pp. 30-31
  16. Martin Fischer: "Turbo-Pascal: High-End-Grafikkarte f r Spieler: GeForce GTX 1080". In: C't 13/2016, pp. 100-103
  17. http://www.golem.de/news/dgx-1-nvidias-supercomputerchen-mit-8x-tesla-p100-1604-120155.html

10 July 2016

Simon D saulniers: [GSOC] Week 5&6 Report

During week 5 and 6, I have been to the debian conference 2016. It was really interesting meeting with a lot of people all so involved in Debian.

Key signing party Each year, this is a really important tradition: people gather together and exchange GPG public key fingerprint and sign each other s keys. This contributes greatly to the growth of the web of trust.
I did exchange public key fingerprint with others. It was the first opportunity become more connected in the PGP web of trust. I think this is something that needs to make its way to the less technical people so that everyone can benefit from the network privacy features. There is support for some mail clients like Thunderbird, but I think there is still work to do there and mostly there is work to do about the opinion or point of view people have about encryption ; people don t care enough and they don t really know what encryption can do for them (digital signature, trust and privacy).

Ring now part of Debian During the first week at debcamp, Alexandre Viau, an employee at Savoir-Faire Linux and a also a Debian developer (DD for short), has packaged Ring for Debian. Users can now install Ring like so:
$ sudo apt-get install ring
This is an important moment as more people are now going to easily try Ring and potentially contribute to it.

Presentating Ring Alexandre Viau and I have been thinking about presenting Ring at debconf 2016. We finally did it.

Joey Hess: twenty years of free software -- part 12 propellor

Propellor is my second big Haskell program. I recently described the motivation for it like this, in a proposal for a Linux.Conf.Au talk:
The configuration of Linux hosts has become increasingly declarative, managed by tools like puppet and ansible, or by the composition of containers. But if a server is a collection of declarative properties, how do you make sure that changes to that configuration make sense? You can test them, but eventually it's 3 AM and you have an emergency fix that needs to go live immediately. Data types to the rescue! While data types are usually used to prevent eg, combining an Int and a Bool, they can be used at a much more abstract level, for example to prevent combining a property that needs a Debian system with a property that needs a Red Hat system. Propellor leverages Haskell's type system to prove the consistency of the properties it will apply to a host.
The real origin story though, is that I wanted to finally start using configuration management, but the tools for it all seemed very complicated and built on shaky foundations (like piles of yaml), and it seemed it would be easier to write my own than deal with that. Meanwhile, I had Haskell burning a hole in my pocket, ready to be used in a second large project after git-annex. Propellor has averaged around 2.5 contributions per month from users since it got started, but increasing numbers recently. That's despite having many fewer users than git-annex, which remember gets perhaps 1 patch per month. Of course, I've "cheated" by making sure that propellor's users know Haskell, or are willing to learn some. And, propellor is very compositional; adding a new property to it is not likely to be complicated by any of the existing code. So it's easy to extend, if you're able to use it. At this point propellor has a small community of regular contributors, and I spend some pleasant weekend afternoons reviewing and merging their work. Much of my best work on propellor has involved keeping the behavior of the program the same while making its types better, to prevent mistakes. Propellor's core data types have evolved much more than in any program I worked on before. That's exciting! Next: twenty years of free software -- part 13 past and future

Bits from Debian: New Debian Developers and Maintainers (May and June 2016)

The following contributors got their Debian Developer accounts in the last two months: The following contributors were added as Debian Maintainers in the last two months: Congratulations!

8 July 2016

Reproducible builds folks: Managing container and environment state

Author: ceridwen With some more help from Martin Pitt, it became clear to me that my previous mental model of how autopkgtest worked is very different from how it does work. I'll illustrate by borrowing my previous example. I know that schroot has the following behavior:
The default behaviour is as follows (all directory paths are inside the chroot). A login shell is run in the current working directory. If this is not available, it will try $HOME (when --preserve-environment is used), then the user's home directory, and / inside the chroot in turn. A command is always run in the current working directory inside the chroot. If none of the directories are available, schroot will exit with an error status.
I was naively thinking that the way autopkgtest would work is that it would set the current working directory of the schroot call and the ensuing subprocess call would thus take place in that directory inside the schroot. That is not how it works. If you want to change directories inside the virtual server, you have to use cd. The same is true of, at least, environment variables, which have their own specific handling in the adt_testbed.Testbed methods but have to be passed as strings, and umask. I'm assuming this is because the direct methods with qemu images or LXC containers don't work. What this means is that I was thinking about the problem the wrong way: what reprotest needs to do is generate shell scripts. This is how autopkgtest works. If this goes beyond laying out commands linearly one after another, for instance if it demands conditionals or other nested constructs, the right way to do it is to build an abstract syntax tree representation of the shell script and then convert it to code. Whether I need more complicated shell scripts depends on my approach to handling state in the containers. I need to know what state persists across separate command executions: if I call adt_testbed.Testbed.execute() twice, what if any changes I make to the container will carry forward from the first to the second? There are three categories here. First, some properties of a system aren't preserved even from one command execution to the next, like working directory and environment variables. (I thought working directory would be preserved, but it's not). The second is state that persists while the testbed is open and is then automatically reverted when it's closed, like files copied into temporary directories on the tesbed. The third is state that persists across different sessions on the same container and must be cleaned up by reprotest. It's worth noting that which state falls into which category may vary by the container in question, though for the most part I can either do unnecessary cleanup or issue unnecessary commands to handle the differences. autopkgtest itself has a very different approach to cleanup, as it relies almost entirely on the builtin reversion capabilities from some of its containers. I would prefer to avoid doing the same, partly because I know that some of the modifications I need to make, for instance creating new users or mounting disorderfs, can't be reverted by the faster, simpler containers like schroot. From discussions with Lunar, I think that the variations that correspond to environment variables (captures_environment, home, locales, path, and timezone) fall into the first category, but because of the special handling for them they don't require sending a separate command. The shell (bash foo) accepts a script or command as an argument so it also doesn't need a separate command. Setting the working directory and umask require separate commands that have to be joined. On Linux, setarch also accepts a command/script as an argument so can be handled like the shell, but there's no unified POSIX protocol for mocking uname so other OSes will require different approaches. Users, groups, file ordering, host, and domain will require cleanup in all containers except for (maybe) qemu. If I want to handle the cleanup in the shell scripts themselves, I need conditionals so that for instance the shell script only tries to unmount disorderfs if disorderfs was successfully mounted. This approach would simplify the error handling problems I've had before, where when a build crashes cleanup code run from Python doesn't get run until after the testbed stop accepting commands. Lunar suggested the Plumbum library to me, and I think I can use it to avoid writing my own shell AST library. It has a method that converts the Python representation of a shell script into a string that can be passed to Testbed.command(). Integrating Plumbum to generate the necessary scripts is where I'm going in the next week. Any feedback on any of this is welcome. I'm also curious what other projects are using autopkgtest code. Holger brought to my attention piuparts, which brings the list up to four that I'm aware of, autopkgtest itself, sbuild, piuparts, and now reprotest.

7 July 2016

Lior Kaplan: Anonymous CVE requests

A year ago I ve blogged about people requesting CVE without letting upstream know. On the other hand, per requests from Debian, I m working on improving PHP upstream CVE request process. For the last few release this means I ask the security list members which issues they think should have CVE and ask for them in parallel to the release being made (usually in the space between the release being tagged publicly and is actually announced). In the last week, I ve encountered a case where a few CVE were assigned to old PHP issues without any public notice. The fixes for these issues have been published a year ago (August 2015). And I find out about these assignment through warning published by the distributions (mostly Debian, which I m close to). Sometimes things fall between the chairs, and it s perfectly OK to ask for CVE to make sure security issues do get attention even if time has passed. But after the issues (and fixes) are public, I don t see a reason to do so without making the request itself public as well. And even if the request wasn t public, at least notify upstream so this info can be added to the right places. Most of these bug were found out when I started to add sequential number into the CVE search after getting an a notice from Debian for two of the issues. And while working on processing these issues for PHP, I also notice they weren t updated for libGD where appropriate (including recent issues). Beyond keeping the eco-system up to date, another aspect of publicity is getting opinions from other parties. For example, in the case of CVE-2015-8879, RedHat doesn t agree with the classification of the bug as security. To give an example of a way things should happen is the request of CVE for PHP 5.5.34 in April, in which the Gentoo security team asked for assignment without upstream knowledge, Debian representative CCs upstream (Thanks!) and also asks CVE for issues covered by Ubuntu, to which the Ubuntu guy then adds some details. I hope this blog post will reach the anonymous people behind these CVE requests, and also the people assigning them. Without transparency and keeping things in synchronization, the idea of having a centralized location for security warning is not going to accomplish its goals.
Filed under: Debian GNU/Linux, PHP

Sean Whitton: Kant and tear gas

Over the past year I ve been refining my understanding of the core claims of Kantian ethics. I ve realised that I have deeply Kantian intuitions about a lot of issues, and I understand these intuitions better now that I can put them in Kantian terms. Consider two exercises of state power: riot police suppressing protesters by non-lethal means, and soldiers shooting protesters to death. I feel more uncomfortable thinking about the first: there s something altogether more sinister about it than the second, even though the second is much more sad. I think that the reason is that non-lethal weaponry is designed to take away people s agency, and it often achieves this aim by means of emotional manipulation. Riot police use so-called baton charges to incite fearful retreat. Protesters have reasoned that in their political situation, they have a duty to resist the incumbent government. Riot police seek to unseat this conviction and cause fear to determine what the protesters will do. In Kantian terms, the riot police fail to respect the moral agency of the protesters by seeking to unseat the moral personality s determination of what the protester will do. A controversial example that Kant uses to make this point is the axe murderer case. Kant asks us to imagine that someone bangs on our front door and begs us to hide him in our house, because someone who wishes to kill him is coming up behind them. We do so. When the axe murderer arrives, he goes door-to-door and asks us whether the intended victim is in each house. Kant says that it is morally wrong to lie to the axe murderer and say that the victim is not in your house. How could this be? Surely there is a moral duty to protect the victim from being killed? Indeed there is, but when it comes into conflict with the duty not to lie, that second duty wins out. That s because respecting the moral agency of individuals is paramount. In this case, we would fail to respect the murderer s agency if we didn t allow him to take the decision to murder or not murder the victim; by lying to him we (disrespectfully) bypass his choice as to whether to do it. It s obviously crazy to say that we are morally required to give up the victim. Kant gives the wrong answer in this case. However, the case definitely reveals a requirement to respect other people s view of what they should do, and give them a chance to do it. Similarly it seems like we shouldn t give semi-automatics to our riot police, but there s something wrong with a lot of what they do. During the recent campaigns about Britain s EU referendum, some criticised Jeremy Corbyn s campaigning on the grounds that he failed to make an emotional appeal, instead asking people to make their own rational decision when they come to cast their vote. So he lost out the emotional appeals other people were making. It seems that he was successfully respecting individual agency. You ve got to give people a chance to live up to their own idea of what they should do. I m not sure how to reconcile these various ideas, and I m not sure what it says about me that I find non-lethal weaponry as uncomfortable as I do.

Daniel Pocock: Can you help with monitoring packages in Debian and Ubuntu?

Debian (and consequently Ubuntu) contains a range of extraordinarily useful monitoring packages. I've been maintaining several of them at a basic level but as more of my time is taken up by free Real-Time Communications software, I haven't been able to follow the latest upstream releases for all of the other packages I maintain. The versions we are distributing now still serve their purpose well, but as some people would like newer versions, I don't want to stand in the way. Monitoring packages are for everyone. Even if you are a single user or developer with a single desktop or laptop and no servers, you may still find some of these packages useful. For example, after doing an apt-get upgrade or dist-upgrade, it can be extremely beneficial to look at your logs in LogAnalyzer with all the errors and warnings colour-coded so you can see at a glance whether your upgrade broke anything. If you are testing new software before a release or trying to troubleshoot erratic behavior, this type of colour-coded feedback can also help you focus on possible problems without the eyestrain of tailing a logfile. LogAnalyzer How to help A good first step is simply looking over the packages maintained by the pkg-monitoring group and discovering whether any of them are useful for your own needs. You may be familiar with alternatives that exist in Debian, if so, feel free to comment on whether you believe any of these packages should be dropped by cre
ating a wishlist bug against the package concerned. The next step is joining the pkg-monitoring mailing list. If you are a Debian Developer or Debian Maintainer with upload rights already, you can join the group on alioth. If you are not at that level yet, you are still very welcome to test new versions of the packages and upload them on mentors.debian.net and then join the mentors mailing list to look for a member of the community who can help review your work and sponsor an upload for you. Each of the packages should have a README.source file in the repository explaining more about how the package is maintained. Familiarity with Git is essential. Note that all of the packages keep their debian/* artifacts in a branch called debian/sid while the master branch tracks the upstream repository. You can clone the Debian package repositories for any of these projects from alioth and build them yourself, try building packages of new upstream versions and try to investigate any of the bug reports submitted to Debian. Some of the bugs may have already been fixed by upstream changes and can be marked appropriately. Integrating your monitoring systems Two particular packages I would like to highlight are ganglia-nagios-bridge and syslog-nagios-bridge. They are not exclusively for Nagios and could also be used with Icinga or other monitoring dashboards. The key benefit of these packages is that all the alerting is consolidated in a single platform, Nagios, which is able to display them in a colour-coded dashboard and intelligently send notifications to people in a manner that is fully configurable. If you haven't integrated your monitoring systems already, these projects provide a simple and lightweight way to start doing so.

5 July 2016

Joey Hess: twenty years of free software -- part 8 github-backup

github-backup is an attempt to take something I don't like -- github's centralization of what should be a decentralized techology -- and find a constrictive way to make it at least meet my baseline requirements for centralized systems. Namely that when they go away, I don't lose data. So, it was written partly with my ArchiveTeam hat on. A recent bug filed on it, Backup fails for repositories unavailable due to DMCA takedown made me happy, because it shows github-backup behaving more or less as intended, although perhaps not in the optimal way. By the way, this is the only one of my projects that uses github for issue tracking. Intentionally ironically. It was my second real Haskell program (after git-annex) and so also served as a good exercise in applying what I'd learned about writing Haskell up to that point. Next: twenty years of free software -- part 9 small projects

4 July 2016

Benjamin Mako Hill: Studying the relationship between remixing & learning

With more than 10 million users, the Scratch online community is the largest online community where kids learn to program. Since it was created, a central goal of the community has been to promote remixing the reworking and recombination of existing creative artifacts. As the video above shows, remixing programming projects in the current web-based version of Scratch is as easy is as clicking on the see inside button in a project web-page, and then clicking on the remix button in the web-based code editor. Today, close to 30% of projects on Scratch are remixes. Remixing plays such a central role in Scratch because its designers believed that remixing can play an important role in learning. After all, Scratch was designed first and foremost as a learning community with its roots in the Constructionist framework developed at MIT by Seymour Papert and his colleagues. The design of the Scratch online community was inspired by Papert s vision of a learning community similar to Brazilian Samba schools (Henry Jenkins writes about his experience of Samba schools in the context of Papert s vision here), and a comment Marvin Minsky made in 1984:
Adults worry a lot these days. Especially, they worry about how to make other people learn more about computers. They want to make us all computer-literate. Literacy means both reading and writing, but most books and courses about computers only tell you about writing programs. Worse, they only tell about commands and instructions and programming-language grammar rules. They hardly ever give examples. But real languages are more than words and grammar rules. There s also literature what people use the language for. No one ever learns a language from being told its grammar rules. We always start with stories about things that interest us.
In a new paper titled Remixing as a pathway to Computational Thinking that was recently published at the ACM Conference on Computer Supported Collaborative Work and Social Computing (CSCW) conference, we used a series of quantitative measures of online behavior to try to uncover evidence that might support the theory that remixing in Scratch is positively associated with learning. scratchblocksOf course, because Scratch is an informal environment with no set path for users, no lesson plan, and no quizzes, measuring learning is an open problem. In our study, we built on two different approaches to measure learning in Scratch. The first approach considers the number of distinct types of programming blocks available in Scratch that a user has used over her lifetime in Scratch (there are 120 in total) something that can be thought of as a block repertoire or vocabulary. This measure has been used to model informal learning in Scratch in an earlier study. Using this approach, we hypothesized that users who remix more will have a faster rate of growth for their code vocabulary. Controlling for a number of factors (e.g. age of user, the general level of activity) we found evidence of a small, but positive relationship between the number of remixes a user has shared and her block vocabulary as measured by the unique blocks she used in her non-remix projects. Intriguingly, we also found a strong association between the number of downloads by a user and her vocabulary growth. One interpretation is that this learning might also be associated with less active forms of appropriation, like the process of reading source code described by Minksy. The second approach we used considered specific concepts in programming, such as loops, or event-handling. To measure this, we utilized a mapping of Scratch blocks to key programming concepts found in this paper by Karen Brennan and Mitchel Resnick. For example, in the image below are all the Scratch blocks mapped to the concept of loop . scratchblocksctWe looked at six concepts in total (conditionals, data, events, loops, operators, and parallelism). In each case, we hypothesized that if someone has had never used a given concept before, they would be more likely to use that concept after encountering it while remixing an existing project. Using this second approach, we found that users who had never used a concept were more likely to do so if they had been exposed to the concept through remixing. Although some concepts were more widely used than others, we found a positive relationship between concept use and exposure through remixing for each of the six concepts. We found that this relationship was true even if we ignored obvious examples of cutting and pasting of blocks of code. In all of these models, we found what we believe is evidence of learning through remixing. Of course, there are many limitations in this work. What we found are all positive correlations we do not know if these relationships are causal. Moreover, our measures do not really tell us whether someone has understood the usage of a given block or programming concept.However, even with these limitations, we are excited by the results of our work, and we plan to build on what we have. Our next steps include developing and utilizing better measures of learning, as well as looking at other methods of appropriation like viewing the source code of a project.

This blog post and the paper it describes are collaborative work with Sayamindu Dasgupta, Andr s Monroy-Hern ndez, and William Hale. The paper is released as open access so anyone can read the entire paper here. This blog post was also posted on Sayamindu Dasgupta s blog and on Medium by the MIT Media Lab.

Paul Wise: Check All The thingS!

check-all-the-things (aka cats, Meow!) is a tool that aims to make it easy to know which tools can be used to check a directory tree and to make it easy to run those tools on the directory tree. The tree could either be a source tree or a build tree or both. It aims to check as much of the tree as possible so the output can be very verbose and have many false positives. It is not for the busy, lazy or noise intolerant. It runs the checks by matching file names and MIME types against those registered for a list of checks. Each check has a set of dependencies, flags, filename wildcards, MIME type wildcards, comments and prerequisite commands. By default it: It runs all checks for the current distro/release except: There are command-line options to customise the behaviour and automatic bash shell completion via argcomplete. There are 177 checks (including TODO ones) in 73 different categories. There are an additional 224 not-well-specified TODO items for new checks in comments. It is exceptionally easy to add new checks once one knows how to use the tool one wants to add. At this point in time it is probably not a good idea to run it in an untrusted directory tree for several reasons: The project initially started as really hacky wiki page full of commands to run. At some point I figured it was time to make this actually be maintainable and started on a project to do that. At around the same time Jakub Wilk was working on maquack to replace the wiki page. Somehow I found out about it and talked to him about it. It was vastly less hacky than my version so I ended up taking it over and continuing it under the check-all-the-things name. I polished it for the last two years and finally released it into Debian unstable during DebCamp16.

3 July 2016

Jonathan McDowell: Confirming all use of an SSH agent

For a long time I ve wanted an ssh-agent setup that would ask me before every use, so I could slightly more comfortably forward authentication over SSH without worrying that my session might get hijacked somewhere at the remote end (I often find myself wanting to pull authenticated git repos on remote hosts). I m at DebConf this week, which is an ideal time to dig further into these things, so I did so today. As is often the case it turns out this is already possible, if you know how. I began with a setup that was using GNOME Keyring to manage my SSH keys. This isn t quite what I want (eventually I want to get to the point that I can sometimes forward a GPG agent to remote hosts for signing purposes as well), so I set about setting up gpg-agent. I used Chris excellent guide to GnuPG/SSH Agent setup as a starting point and ended up doing the following:
$ echo use-agent >> ~/.gnupg/options
$ echo enable-ssh-support >> ~/.gnupg/gpg-agent.conf
$ sudo sed -i.bak "s/^use-ssh-agent/# use-ssh-agent/" /etc/X11/Xsession.options
$ sudo rm /etc/xdg/autostart/gnome-keyring-ssh.desktop
The first 2 commands setup my local agent, and told it to do SSH agent foo. The next stopped X from firing up ssh-agent, and the final one prevents GNOME Keyring from being configured to be the SSH agent, without having to remove libpam-gnome-keyring as Chris did. After the above I logged out of and into X again, and could see ~/.gnupg/S.gpg-agent.ssh getting created and env grep SSH showing SSH_AUTH_SOCK pointing to it (if GNOME Keyring is still handling things it ends up pointing to something like /run/user/1000/keyring/ssh). [Update: Luca Capello emailed to point out this was a bad approach; there s thankfully no need to do the last 2 commands that require root. #767341 removed the need to edit Xsession.options and you can prevent GNOME Keyring starting on a per user basis with:
(cat /etc/xdg/autostart/gnome-keyring-ssh.desktop ;
 echo 'X-GNOME-Autostart-enabled=false') > \
 ~/.config/autostart/gnome-keyring-ssh.desktop
] After this it turned out all I need to do was ssh-add -c <ssh keyfile>. The -c says confirm use and results in the confirm flag being appended to the end of ~/.gnupg/sshcontrol (so if you ve already done the ssh-add you can go and add the confirm if that s the behaviour you d like). Simple when you know how, but I ve had conversations with several people in the past who wanted the same thing and hadn t figured out how, so hopefully this is helpful to others.

Russ Allbery: Review: Coming Home

Review: Coming Home, by Jack McDevitt
Series: Alex Benedict #7
Publisher: Ace
Copyright: November 2014
Printing: November 2015
ISBN: 0-425-26088-7
Format: Mass market
Pages: 356
Coming Home is a direct sequel to Firebird, the first time McDevitt has done that in this series. You therefore don't want to start here, although the nature of the sequel doesn't require that you remember Firebird in that much detail. The mystery of the disappearing starships was understood in Firebird but not resolved. The title advertises that as a major theme in this book, but it progresses very slowly. There's more media bickering and various factional attempts to draw Alex (and, to a lesser extent, Chase) into the controversies. McDevitt does a good job writing popular media, the strange position of public intellectual and talk-show favorite, and the way this filters into popular arguments. But with Alex trying to take a nuanced and unsure position and with a lot of talk but little action, it's not the most compelling reading. Coming Home holds to form in balancing a mystery and a second plot. Since the starship problem is understood, it can't be the central mystery of the book. That role is taken by the discovery of communication device from the very early days of space flight, which takes Alex and Chase to Earth for the first time in this series (at least that I can recall). This time, the search is for a legendary trove of historical artifacts that was moved from a space flight museum in Florida when the ocean rose to cover the state. From there, its location was lost in the middle of a general economic collapse called the Time of Troubles that destroyed most of Earth's governmental systems (and, apparently rather more importantly to McDevitt, the space program). Anyone who has gotten this far in the series will know the standard problem with McDevitt's futures: they're indistinguishable from the 1960s except that they have flying cars. There is a tiny break from that tradition here, since climate change has clearly happened to Earth, covering Florida with the ocean and shifting the major cities north. But the sense of deep history that McDevitt is trying for in this series doesn't work: I just don't believe as much time has gone by as the story claims. He does offer an explanation for why technology has been stagnant for apparently millennia, but it's just a contention that science ran out of more things to discover due to authorial fiat and is now just a matter of engineering and step-wise refinement. (I think the science behind the disappearing starships happening in this very same book undermines that contention considerably.) Even if one can put that aside, Earth is, well, boring. This is partly an intriguing stylistic choice by McDevitt: Earth is intended to be just one more world. It might have a longer history than many other human-occupied worlds, but history is so long everywhere that this only matters to a few people like Alex and Chase. The choice makes sense, but it doesn't make a good story. And there are other things that I flatly didn't believe, such as the supposed isolation of Earth from the communication network of Alex's home world of Rimway for... no apparent reason other than that different communication networks don't talk to each other except via, essentially, letters. Even if one is willing to ignore the mysterious failure of forward progress in technology, this makes no social or engineering sense given the capabilities already shown in the series. I found the main mystery at best mildly interesting. McDevitt does a good job showing the research and investigation process, with all its tedium and dead ends, but I wasn't as invested in the search as he wanted me to be. The endless space boosterism started getting on my nerves, as it so often does in science fiction of a certain type, and I had a much harder time swallowing McDevitt's Earth than his fictional Rimway. I will give him credit for a surprisingly affecting conclusion of the main mystery, but the missing starship subplot putters to an undistinguished end. I think this series is running out of steam. It's become increasingly formulaic, and the characters, like McDevitt's future technology, have stopped developing. I was hoping the reunion foreshadowed since Firebird would shake things up, but at least in this book it doesn't. Maybe it will in subsequent books, but I'm starting to question whether I really want to keep reading. Rating: 5 out of 10

2 July 2016

Russ Allbery: Review: Ashes of Honor

Review: Ashes of Honor, by Seanan McGuire
Series: October Daye #6
Publisher: DAW
Copyright: September 2012
ISBN: 1-101-59480-2
Format: Kindle
Pages: 368
This is the sixth book in the October Daye series, contains payoffs for some relationships that have been building over the whole series, and involves entangled politics set up by previous books. It's not the place to start with the series. Ashes of Honor starts, as so many of Toby's books do, with a friend asking her for help. But this request is entirely unexpected, and the help needed comes as a complete surprise: a previously unknown changeling, who has disappeared. A changeling whose powers are completely out of control, and who poses a threat to reality itself. As Toby's cases go, this involves a lot fewer horrible things happening to her and a lot more faerie politics and maneuvering than usual. I appreciated that; I'm not as fond of the books that go deep into despair or desperation. It does involve Toby getting almost killed multiple times, but, due to earlier events of the series, that isn't quite as bad as it used to be. More focus on investigation and political maneuvering and less Toby braving her way through horrors works for me. Even more notably, this book marks Toby finally figuring out that she has friends and allies who are there to help, not just be obligations she feels overwhelmed by or aid that she's not allowed to accept. This was one of her most frustrating characteristics; it's a relief to see her finally relax. This opens the way not only for deeper friendships and more complex plots but also a relationship that I've been awaiting for the entire series, and it's as much fun as I was hoping it would be. Toby started the series rather messed up and unwilling to let anyone close. It was for understandable reasons, but I like her better when she realizes why people respect her. Toby's connections with the royalty of the Bay Area also allow McGuire to tell a political story that moves farther afield from the Shadowed Hills. First in One Salt Sea and now in Ashes of Honor we see more of local politics, more of the lore of McGuire's universe, and another dangerous queen. Toby is particularly fun when she's dangerously outflanking people with considerably more power than she has. At this point, you could call it a specialty. I thought McGuire's take on San Jose and the sort of person who would be in charge of its fae was on point. We also get more of the Luidaeg, which is always a good sign for a Toby novel, and more of Tybalt, who is entangled in a major subplot of the story. Next to Luidaeg, Tybalt is my favorite of Toby's friends, so this book is full of the things that make me happy. McGuire adds some more pieces to her transplanted Celtic mythology and some tantalizing hints of what the fae have left behind. I'm hoping we see more of that in future books. (I suspect that may be what this whole series is building up to.) The story doesn't have quite as much oomph as One Salt Sea, but it's still one of the best books in the series so far. If you've enjoyed the series up to this point, keep reading. Followed by Chimes at Midnight. Rating: 8 out of 10

1 July 2016

Joachim Breitner: When to reroll a six

This is a story about counter-intuitive probabilities and how a small bit of doubt turned out to be very justified. It begins with the game To Court the King (German: Um Krone und Kragen ). It is a nice game with dice and cards, where you start with a few dice, and use your dice rolls to buy additional cards, which give you extra dice or special powers to modify the dice that you rolled. You can actually roll your dice many times, but every time, you have to set aside at least one die, which you can no longer change or reroll, until eventually all dice have been set aside. A few years ago, I have played this game a lot, both online (on yucata.de) as well as in real life. It soon became apparent that it is almost always better to go for the cards that give you an extra die, instead of those that let you modify the dice. Intuitively, this is because every additional die allows you to re-roll your dice once more. I concluded that if I have a certain number of dice (say, n), and I want to have a sum as high as possible at the end, then it may make sense to reroll as many dice as possible, setting aside only those showing a 6 (because that is the best you can get) or, if there is no dice showing a 6, then a single die with the best score. Besides for small number of dice (2 or 3), where even a 4 or 5 is worth keeping, this seemed to be a simple, obvious and correct strategy to maximize the expected outcome of this simplified game. It is definitely simple and obvious. But some doubt that it was correct remained. Having one more die still in the game (i.e. not set aside) definitely improves your expected score, because you can reroll the dice more often. How large is this advantage? What if it ever exceeds 6 then it would make sense to reroll a 6. The thought was strange, but I could not dismiss it. So I did what one does these days if one has a question: I posed it on the mathematics site of StackExchange. That was January 2015, and nothing happened. I tried to answer it myself a month later, or at least work towards at an answer, and did that by brute force. Using a library for probabilistic calculations for Haskell I could write some code that simply calculated the various expected values of n dice for up to n = 9 (beyond that, my unoptimized code would take too long):
1:  3.50000 (+3.50000)
2:  8.23611 (+4.73611)
3: 13.42490 (+5.18879)
4: 18.84364 (+5.41874)
5: 24.43605 (+5.59241)
6: 30.15198 (+5.71592)
7: 35.95216 (+5.80018)
8: 41.80969 (+5.85753)
9: 47.70676 (+5.89707)
Note that this calculation, although printed as floating point numbers, is performed using fractions of unbounded integers, so there are no rounding issues that could skew the result. The result supported the hypothesis that there is no point in rolling a 6 again: The value of an additional die grows and approaches 6 from beyond, but judging from these number is never going to reach it. Then again nothing happened. Until 14 month later, when some Byron Schmuland came along, found this an interesting puzzle, and set out a 500 point bounty to whoever solved this problem. This attracted a bit attention, and a few not very successful attempts at solving this. Eventually it reached twitter, where Roman Cheplyaka linked to it. Coincidally a day later some joriki came along, and he had a very good idea: Why not make our life easier and think about dice with less sides, and look at 3 instead of 6. This way, and using a more efficient implementation (but still properly using rationals), he could do a similar calculation for up to 50 dice. And it was very lucky that he went to 50, and not just 25, because up to 27, the results were very much as expected, approaching value of +3 from below. But then it surpassed +3 and became +3.000000008463403. In other words: If you have roll 28 dice, and you have exactly two dice showing a 3, then it gives you better expected score if you set aside only one 3, and not both of them. The advantage is minuscule, but that does not matter it is there. From then on, the results behaved strangely. Between 28 and 34, the additional value was larger than 3. Then, from 35 on again lower than 2. It oscillated. Something similar could be observed when the game is played with coins. Eventually, joriki improved his code and applied enough tricks so that he could solve it also for the 6-sided die: The difference of the expected value of 198 dice and having 199 dice is larger than 6 (by 10 21...)! The optimizations that allowed him to calculate these numbers in a reasonable amount of time unfortunately was to assume that my original hypothesis (never rerolling a 6 is optimal), which held until n < 199. But this meant that for n > 199, the code did not yield correct results. What is the rationale of the story? Don t trust common sense when it comes to statistics; don t judge a sequence just from a few initial numbers; if you have an interesting question, post it online and wait for 16 months.

Leo 'costela' Antunes: Yet another letsencrypt (ACME) client

Well, I apparently joined the hordes of people writing ACME (the Protocol behind Let s Encrypt) clients. Like the fairy tale Goldilocks, I couldn t find a client in the right spot between minimalistic and full-featured for my needs: acme-tiny was too bare-bones; the official letsencrypt client (now called certbot) too huge; and simp_le came very close, but it s support for pluggable certificate formats made it just a bit too big for me. So, wile (named after another famous user of ACME products) was born. Maybe it will fill someone else s very subjective needs.

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