Measurements Keep in mind that these are one-time measurements. They should be indicative of actual performance, but your experience may vary.

ack (small Perl program)

distribution	package manager	data	wall-clock time	rate
Fedora	dnf	114 MB	33s	3.4 MB/s
Debian	apt	16 MB	10s	1.6 MB/s
NixOS	Nix	15 MB	5s	3.0 MB/s
Arch Linux	pacman	6.5 MB	3s	2.1 MB/s
Alpine	apk	10 MB	1s	10.0 MB/s

qemu (large C program)

distribution	package manager	data	wall-clock time	rate
Fedora	dnf	226 MB	4m37s	1.2 MB/s
Debian	apt	224 MB	1m35s	2.3 MB/s
Arch Linux	pacman	142 MB	44s	3.2 MB/s
NixOS	Nix	180 MB	34s	5.2 MB/s
Alpine	apk	26 MB	2.4s	10.8 MB/s

(Looking for older measurements? See Appendix B (2019). The difference between the slowest and fastest package managers is 30x! How can Alpine s apk and Arch Linux s pacman be an order of magnitude faster than the rest? They are doing a lot less than the others, and more efficiently, too.

Pain point: too much metadata For example, Fedora transfers a lot more data than others because its main package list is 60 MB (compressed!) alone. Compare that with Alpine s 734 KB APKINDEX.tar.gz. Of course the extra metadata which Fedora provides helps some use case, otherwise they hopefully would have removed it altogether. The amount of metadata seems excessive for the use case of installing a single package, which I consider the main use-case of an interactive package manager. I expect any modern Linux distribution to only transfer absolutely required data to complete my task.

Pain point: no concurrency Because they need to sequence executing arbitrary package maintainer-provided code (hooks and triggers), all tested package managers need to install packages sequentially (one after the other) instead of concurrently (all at the same time). In my blog post Can we do without hooks and triggers? , I outline that hooks and triggers are not strictly necessary to build a working Linux distribution.

Thought experiment: further speed-ups Strictly speaking, the only required feature of a package manager is to make available the package contents so that the package can be used: a program can be started, a kernel module can be loaded, etc. By only implementing what s needed for this feature, and nothing more, a package manager could likely beat apk s performance. It could, for example:

• skip archive extraction by mounting file system images (like AppImage or snappy)
• use compression which is light on CPU, as networks are fast (like apk)
• skip fsync when it is safe to do so, i.e.:
  • package installations don t modify system state
  • atomic package installation (e.g. an append-only package store)
  • automatically clean up the package store after crashes

Current landscape Here s a table outlining how the various package managers listed on Wikipedia s list of software package management systems fare:

name	scope	package file format	hooks/triggers
AppImage	apps	image: ISO9660, SquashFS	no
snappy	apps	image: SquashFS	yes: hooks
FlatPak	apps	archive: OSTree	no
0install	apps	archive: tar.bz2	no
nix, guix	distro	archive: nar. bz2,xz	activation script
dpkg	distro	archive: tar. gz,xz,bz2 in ar(1)	yes
rpm	distro	archive: cpio. bz2,lz,xz	scriptlets
pacman	distro	archive: tar.xz	install
slackware	distro	archive: tar. gz,xz	yes: doinst.sh
apk	distro	archive: tar.gz	yes: .post-install
Entropy	distro	archive: tar.bz2	yes
ipkg, opkg	distro	archive: tar ,.gz	yes

Conclusion As per the current landscape, there is no distribution-scoped package manager which uses images and leaves out hooks and triggers, not even in smaller Linux distributions. I think that space is really interesting, as it uses a minimal design to achieve significant real-world speed-ups. I have explored this idea in much more detail, and am happy to talk more about it in my post Introducing the distri research linux distribution".

Appendix A: related work There are a couple of recent developments going into the same direction:

• Revisiting How We Put Together Linux Systems describes mounting app bundles
• Android Q uses ext4 loopback images
• The Haiku Operating System s package manager Haiku Depot uses images

Appendix C: measurement details (2020)

ack You can expand each of these:

Fedora s dnf takes almost 33 seconds to fetch and unpack 114 MB.

% docker run -t -i fedora /bin/bash
[root@62d3cae2e2f9 /]# time dnf install -y ack
Fedora 32 openh264 (From Cisco) - x86_64     1.9 kB/s   2.5 kB     00:01
Fedora Modular 32 - x86_64                   6.8 MB/s   4.9 MB     00:00
Fedora Modular 32 - x86_64 - Updates         5.6 MB/s   3.7 MB     00:00
Fedora 32 - x86_64 - Updates                 9.9 MB/s    23 MB     00:02
Fedora 32 - x86_64                            39 MB/s    70 MB     00:01
[ ]
real	0m32.898s
user	0m25.121s
sys	0m1.408s

NixOS s Nix takes a little over 5s to fetch and unpack 15 MB.

% docker run -t -i nixos/nix
39e9186422ba:/# time sh -c 'nix-channel --update && nix-env -iA nixpkgs.ack'
unpacking channels...
created 1 symlinks in user environment
installing 'perl5.32.0-ack-3.3.1'
these paths will be fetched (15.55 MiB download, 85.51 MiB unpacked):
  /nix/store/34l8jdg76kmwl1nbbq84r2gka0kw6rc8-perl5.32.0-ack-3.3.1-man
  /nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31
  /nix/store/9fd4pjaxpjyyxvvmxy43y392l7yvcwy1-perl5.32.0-File-Next-1.18
  /nix/store/czc3c1apx55s37qx4vadqhn3fhikchxi-libunistring-0.9.10
  /nix/store/dj6n505iqrk7srn96a27jfp3i0zgwa1l-acl-2.2.53
  /nix/store/ifayp0kvijq0n4x0bv51iqrb0yzyz77g-perl-5.32.0
  /nix/store/w9wc0d31p4z93cbgxijws03j5s2c4gyf-coreutils-8.31
  /nix/store/xim9l8hym4iga6d4azam4m0k0p1nw2rm-libidn2-2.3.0
  /nix/store/y7i47qjmf10i1ngpnsavv88zjagypycd-attr-2.4.48
  /nix/store/z45mp61h51ksxz28gds5110rf3wmqpdc-perl5.32.0-ack-3.3.1
copying path '/nix/store/34l8jdg76kmwl1nbbq84r2gka0kw6rc8-perl5.32.0-ack-3.3.1-man' from 'https://cache.nixos.org'...
copying path '/nix/store/czc3c1apx55s37qx4vadqhn3fhikchxi-libunistring-0.9.10' from 'https://cache.nixos.org'...
copying path '/nix/store/9fd4pjaxpjyyxvvmxy43y392l7yvcwy1-perl5.32.0-File-Next-1.18' from 'https://cache.nixos.org'...
copying path '/nix/store/xim9l8hym4iga6d4azam4m0k0p1nw2rm-libidn2-2.3.0' from 'https://cache.nixos.org'...
copying path '/nix/store/9df65igwjmf2wbw0gbrrgair6piqjgmi-glibc-2.31' from 'https://cache.nixos.org'...
copying path '/nix/store/y7i47qjmf10i1ngpnsavv88zjagypycd-attr-2.4.48' from 'https://cache.nixos.org'...
copying path '/nix/store/dj6n505iqrk7srn96a27jfp3i0zgwa1l-acl-2.2.53' from 'https://cache.nixos.org'...
copying path '/nix/store/w9wc0d31p4z93cbgxijws03j5s2c4gyf-coreutils-8.31' from 'https://cache.nixos.org'...
copying path '/nix/store/ifayp0kvijq0n4x0bv51iqrb0yzyz77g-perl-5.32.0' from 'https://cache.nixos.org'...
copying path '/nix/store/z45mp61h51ksxz28gds5110rf3wmqpdc-perl5.32.0-ack-3.3.1' from 'https://cache.nixos.org'...
building '/nix/store/m0rl62grplq7w7k3zqhlcz2hs99y332l-user-environment.drv'...
created 49 symlinks in user environment
real	0m 5.60s
user	0m 3.21s
sys	0m 1.66s

Debian s apt takes almost 10 seconds to fetch and unpack 16 MB.

% docker run -t -i debian:sid
root@1996bb94a2d1:/# time (apt update && apt install -y ack-grep)
Get:1 http://deb.debian.org/debian sid InRelease [146 kB]
Get:2 http://deb.debian.org/debian sid/main amd64 Packages [8400 kB]
Fetched 8546 kB in 1s (8088 kB/s)
[ ]
The following NEW packages will be installed:
  ack libfile-next-perl libgdbm-compat4 libgdbm6 libperl5.30 netbase perl perl-modules-5.30
0 upgraded, 8 newly installed, 0 to remove and 23 not upgraded.
Need to get 7341 kB of archives.
After this operation, 46.7 MB of additional disk space will be used.
[ ]
real	0m9.544s
user	0m2.839s
sys	0m0.775s

Arch Linux s pacman takes a little under 3s to fetch and unpack 6.5 MB.

% docker run -t -i archlinux/base
[root@9f6672688a64 /]# time (pacman -Sy && pacman -S --noconfirm ack)
:: Synchronizing package databases...
 core            130.8 KiB  1090 KiB/s 00:00
 extra          1655.8 KiB  3.48 MiB/s 00:00
 community         5.2 MiB  6.11 MiB/s 00:01
resolving dependencies...
looking for conflicting packages...
Packages (2) perl-file-next-1.18-2  ack-3.4.0-1
Total Download Size:   0.07 MiB
Total Installed Size:  0.19 MiB
[ ]
real	0m2.936s
user	0m0.375s
sys	0m0.160s

Alpine s apk takes a little over 1 second to fetch and unpack 10 MB.

% docker run -t -i alpine
fetch http://dl-cdn.alpinelinux.org/alpine/v3.12/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.12/community/x86_64/APKINDEX.tar.gz
(1/4) Installing libbz2 (1.0.8-r1)
(2/4) Installing perl (5.30.3-r0)
(3/4) Installing perl-file-next (1.18-r0)
(4/4) Installing ack (3.3.1-r0)
Executing busybox-1.31.1-r16.trigger
OK: 43 MiB in 18 packages
real	0m 1.24s
user	0m 0.40s
sys	0m 0.15s

qemu You can expand each of these:

Fedora s dnf takes over 4 minutes to fetch and unpack 226 MB.

% docker run -t -i fedora /bin/bash
[root@6a52ecfc3afa /]# time dnf install -y qemu
Fedora 32 openh264 (From Cisco) - x86_64     3.1 kB/s   2.5 kB     00:00
Fedora Modular 32 - x86_64                   6.3 MB/s   4.9 MB     00:00
Fedora Modular 32 - x86_64 - Updates         6.0 MB/s   3.7 MB     00:00
Fedora 32 - x86_64 - Updates                 334 kB/s    23 MB     01:10
Fedora 32 - x86_64                            33 MB/s    70 MB     00:02
[ ]
Total download size: 181 M
Downloading Packages:
[ ]
real	4m37.652s
user	0m38.239s
sys	0m6.321s

NixOS s Nix takes almost 34s to fetch and unpack 180 MB.

% docker run -t -i nixos/nix
83971cf79f7e:/# time sh -c 'nix-channel --update && nix-env -iA nixpkgs.qemu'
unpacking channels...
created 1 symlinks in user environment
installing 'qemu-5.1.0'
these paths will be fetched (180.70 MiB download, 1146.92 MiB unpacked):
[ ]
real	0m 33.64s
user	0m 16.96s
sys	0m 3.05s

Debian s apt takes over 95 seconds to fetch and unpack 224 MB.

% docker run -t -i debian:sid
root@b7cc25a927ab:/# time (apt update && apt install -y qemu-system-x86)
Get:1 http://deb.debian.org/debian sid InRelease [146 kB]
Get:2 http://deb.debian.org/debian sid/main amd64 Packages [8400 kB]
Fetched 8546 kB in 1s (5998 kB/s)
[ ]
Fetched 216 MB in 43s (5006 kB/s)
[ ]
real	1m25.375s
user	0m29.163s
sys	0m12.835s

Arch Linux s pacman takes almost 44s to fetch and unpack 142 MB.

% docker run -t -i archlinux/base
[root@58c78bda08e8 /]# time (pacman -Sy && pacman -S --noconfirm qemu)
:: Synchronizing package databases...
 core          130.8 KiB  1055 KiB/s 00:00
 extra        1655.8 KiB  3.70 MiB/s 00:00
 community       5.2 MiB  7.89 MiB/s 00:01
[ ]
Total Download Size:   135.46 MiB
Total Installed Size:  661.05 MiB
[ ]
real	0m43.901s
user	0m4.980s
sys	0m2.615s

Alpine s apk takes only about 2.4 seconds to fetch and unpack 26 MB.

% docker run -t -i alpine
/ # time apk add qemu-system-x86_64
fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/community/x86_64/APKINDEX.tar.gz
[ ]
OK: 78 MiB in 95 packages
real	0m 2.43s
user	0m 0.46s
sys	0m 0.09s

Appendix B: measurement details (2019)

ack You can expand each of these:

Fedora s dnf takes almost 30 seconds to fetch and unpack 107 MB.

% docker run -t -i fedora /bin/bash
[root@722e6df10258 /]# time dnf install -y ack
Fedora Modular 30 - x86_64            4.4 MB/s   2.7 MB     00:00
Fedora Modular 30 - x86_64 - Updates  3.7 MB/s   2.4 MB     00:00
Fedora 30 - x86_64 - Updates           17 MB/s    19 MB     00:01
Fedora 30 - x86_64                     31 MB/s    70 MB     00:02
[ ]
Install  44 Packages
Total download size: 13 M
Installed size: 42 M
[ ]
real	0m29.498s
user	0m22.954s
sys	0m1.085s

NixOS s Nix takes 14s to fetch and unpack 15 MB.

% docker run -t -i nixos/nix
39e9186422ba:/# time sh -c 'nix-channel --update && nix-env -i perl5.28.2-ack-2.28'
unpacking channels...
created 2 symlinks in user environment
installing 'perl5.28.2-ack-2.28'
these paths will be fetched (14.91 MiB download, 80.83 MiB unpacked):
  /nix/store/57iv2vch31v8plcjrk97lcw1zbwb2n9r-perl-5.28.2
  /nix/store/89gi8cbp8l5sf0m8pgynp2mh1c6pk1gk-attr-2.4.48
  /nix/store/gkrpl3k6s43fkg71n0269yq3p1f0al88-perl5.28.2-ack-2.28-man
  /nix/store/iykxb0bmfjmi7s53kfg6pjbfpd8jmza6-glibc-2.27
  /nix/store/k8lhqzpaaymshchz8ky3z4653h4kln9d-coreutils-8.31
  /nix/store/svgkibi7105pm151prywndsgvmc4qvzs-acl-2.2.53
  /nix/store/x4knf14z1p0ci72gl314i7vza93iy7yc-perl5.28.2-File-Next-1.16
  /nix/store/zfj7ria2kwqzqj9dh91kj9kwsynxdfk0-perl5.28.2-ack-2.28
copying path '/nix/store/gkrpl3k6s43fkg71n0269yq3p1f0al88-perl5.28.2-ack-2.28-man' from 'https://cache.nixos.org'...
copying path '/nix/store/iykxb0bmfjmi7s53kfg6pjbfpd8jmza6-glibc-2.27' from 'https://cache.nixos.org'...
copying path '/nix/store/x4knf14z1p0ci72gl314i7vza93iy7yc-perl5.28.2-File-Next-1.16' from 'https://cache.nixos.org'...
copying path '/nix/store/89gi8cbp8l5sf0m8pgynp2mh1c6pk1gk-attr-2.4.48' from 'https://cache.nixos.org'...
copying path '/nix/store/svgkibi7105pm151prywndsgvmc4qvzs-acl-2.2.53' from 'https://cache.nixos.org'...
copying path '/nix/store/k8lhqzpaaymshchz8ky3z4653h4kln9d-coreutils-8.31' from 'https://cache.nixos.org'...
copying path '/nix/store/57iv2vch31v8plcjrk97lcw1zbwb2n9r-perl-5.28.2' from 'https://cache.nixos.org'...
copying path '/nix/store/zfj7ria2kwqzqj9dh91kj9kwsynxdfk0-perl5.28.2-ack-2.28' from 'https://cache.nixos.org'...
building '/nix/store/q3243sjg91x1m8ipl0sj5gjzpnbgxrqw-user-environment.drv'...
created 56 symlinks in user environment
real	0m 14.02s
user	0m 8.83s
sys	0m 2.69s

Debian s apt takes almost 10 seconds to fetch and unpack 16 MB.

% docker run -t -i debian:sid
root@b7cc25a927ab:/# time (apt update && apt install -y ack-grep)
Get:1 http://cdn-fastly.deb.debian.org/debian sid InRelease [233 kB]
Get:2 http://cdn-fastly.deb.debian.org/debian sid/main amd64 Packages [8270 kB]
Fetched 8502 kB in 2s (4764 kB/s)
[ ]
The following NEW packages will be installed:
  ack ack-grep libfile-next-perl libgdbm-compat4 libgdbm5 libperl5.26 netbase perl perl-modules-5.26
The following packages will be upgraded:
  perl-base
1 upgraded, 9 newly installed, 0 to remove and 60 not upgraded.
Need to get 8238 kB of archives.
After this operation, 42.3 MB of additional disk space will be used.
[ ]
real	0m9.096s
user	0m2.616s
sys	0m0.441s

Arch Linux s pacman takes a little over 3s to fetch and unpack 6.5 MB.

% docker run -t -i archlinux/base
[root@9604e4ae2367 /]# time (pacman -Sy && pacman -S --noconfirm ack)
:: Synchronizing package databases...
 core            132.2 KiB  1033K/s 00:00
 extra          1629.6 KiB  2.95M/s 00:01
 community         4.9 MiB  5.75M/s 00:01
[ ]
Total Download Size:   0.07 MiB
Total Installed Size:  0.19 MiB
[ ]
real	0m3.354s
user	0m0.224s
sys	0m0.049s

Alpine s apk takes only about 1 second to fetch and unpack 10 MB.

% docker run -t -i alpine
/ # time apk add ack
fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/community/x86_64/APKINDEX.tar.gz
(1/4) Installing perl-file-next (1.16-r0)
(2/4) Installing libbz2 (1.0.6-r7)
(3/4) Installing perl (5.28.2-r1)
(4/4) Installing ack (3.0.0-r0)
Executing busybox-1.30.1-r2.trigger
OK: 44 MiB in 18 packages
real	0m 0.96s
user	0m 0.25s
sys	0m 0.07s

qemu You can expand each of these:

Fedora s dnf takes over a minute to fetch and unpack 266 MB.

% docker run -t -i fedora /bin/bash
[root@722e6df10258 /]# time dnf install -y qemu
Fedora Modular 30 - x86_64            3.1 MB/s   2.7 MB     00:00
Fedora Modular 30 - x86_64 - Updates  2.7 MB/s   2.4 MB     00:00
Fedora 30 - x86_64 - Updates           20 MB/s    19 MB     00:00
Fedora 30 - x86_64                     31 MB/s    70 MB     00:02
[ ]
Install  262 Packages
Upgrade    4 Packages
Total download size: 172 M
[ ]
real	1m7.877s
user	0m44.237s
sys	0m3.258s

NixOS s Nix takes 38s to fetch and unpack 262 MB.

% docker run -t -i nixos/nix
39e9186422ba:/# time sh -c 'nix-channel --update && nix-env -i qemu-4.0.0'
unpacking channels...
created 2 symlinks in user environment
installing 'qemu-4.0.0'
these paths will be fetched (262.18 MiB download, 1364.54 MiB unpacked):
[ ]
real	0m 38.49s
user	0m 26.52s
sys	0m 4.43s

Debian s apt takes 51 seconds to fetch and unpack 159 MB.

% docker run -t -i debian:sid
root@b7cc25a927ab:/# time (apt update && apt install -y qemu-system-x86)
Get:1 http://cdn-fastly.deb.debian.org/debian sid InRelease [149 kB]
Get:2 http://cdn-fastly.deb.debian.org/debian sid/main amd64 Packages [8426 kB]
Fetched 8574 kB in 1s (6716 kB/s)
[ ]
Fetched 151 MB in 2s (64.6 MB/s)
[ ]
real	0m51.583s
user	0m15.671s
sys	0m3.732s

Arch Linux s pacman takes 1m2s to fetch and unpack 124 MB.

% docker run -t -i archlinux/base
[root@9604e4ae2367 /]# time (pacman -Sy && pacman -S --noconfirm qemu)
:: Synchronizing package databases...
 core       132.2 KiB   751K/s 00:00
 extra     1629.6 KiB  3.04M/s 00:01
 community    4.9 MiB  6.16M/s 00:01
[ ]
Total Download Size:   123.20 MiB
Total Installed Size:  587.84 MiB
[ ]
real	1m2.475s
user	0m9.272s
sys	0m2.458s

Alpine s apk takes only about 2.4 seconds to fetch and unpack 26 MB.

% docker run -t -i alpine
/ # time apk add qemu-system-x86_64
fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.10/community/x86_64/APKINDEX.tar.gz
[ ]
OK: 78 MiB in 95 packages
real	0m 2.43s
user	0m 0.46s
sys	0m 0.09s

Motivation Over the last few months, I have been developing a new index format for Debian Code Search. This required a lot of careful refactoring, re-implementation, debug tool creation and debugging. Multiple factors motivated my work on a new index format:

1. The existing index format has a 2G size limit, into which we have bumped a few times, requiring manual intervention to keep the system running.
2. Debugging the existing system required creating ad-hoc debugging tools, which made debugging sessions unnecessarily lengthy and painful.
3. I wanted to check whether switching to a different integer compression format would improve performance (it does not).
4. I wanted to check whether storing positions with the posting lists would improve performance of identifier queries (= queries which are not using any regular expression features), which make up 78.2% of all Debian Code Search queries (it does).

I figured building a new index from scratch was the easiest approach, compared to refactoring the existing index to increase the size limit (point ). I also figured it would be a good idea to develop the debugging tool in lock step with the index format so that I can be sure the tool works and is useful (point ).

Integer compression: TurboPFor As a quick refresher, search engines typically store document IDs (representing source code files, in our case) in an ordered list ( posting list ). It usually makes sense to apply at least a rudimentary level of compression: our existing system used variable integer encoding. TurboPFor, the self-proclaimed Fastest Integer Compression library, combines an advanced on-disk format with a carefully tuned SIMD implementation to reach better speeds (in micro benchmarks) at less disk usage than Russ Cox s varint implementation in github.com/google/codesearch. If you are curious about its inner workings, check out my TurboPFor: an analysis . Applied on the Debian Code Search index, TurboPFor indeed compresses integers better:

Disk space

8.9G codesearch varint index

5.5G TurboPFor index Switching to TurboPFor (via cgo) for storing and reading the index results in a slight speed-up of a dcs replay benchmark, which is more pronounced the more i/o is required.

Query speed (regexp, cold page cache)

18s codesearch varint index

14s TurboPFor index (cgo)

Query speed (regexp, warm page cache)

15s codesearch varint index

14s TurboPFor index (cgo) Overall, TurboPFor is an all-around improvement in efficiency, albeit with a high cost in implementation complexity.

Positional index: trade more disk for faster queries This section builds on the previous section: all figures come from the TurboPFor index, which can optionally support positions. Conceptually, we re going from:

type docid uint32
type index map[trigram][]docid

to:

type occurrence struct  
    doc docid
    pos uint32 // byte offset in doc
 
type index map[trigram][]occurrence

The resulting index consumes more disk space, but can be queried faster:

1. We can do fewer queries: instead of reading all the posting lists for all the trigrams, we can read the posting lists for the query s first and last trigram only.
   This is one of the tricks described in the paper AS-Index: A Structure For String Search Using n-grams and Algebraic Signatures (PDF), and goes a long way without incurring the complexity, computational cost and additional disk usage of calculating algebraic signatures.
2. Verifying the delta between the last and first position matches the length of the query term significantly reduces the number of files to read (lower false positive rate).
3. The matching phase is quicker: instead of locating the query term in the file, we only need to compare a few bytes at a known offset for equality.
4. More data is read sequentially (from the index), which is faster.

Disk space A positional index consumes significantly more disk space, but not so much as to pose a challenge: a Hetzner EX61-NVME dedicated server ( 64 /month) provides 1 TB worth of fast NVMe flash storage.

6.5G non-positional

123G positional

93G positional (posrel) The idea behind the positional index (posrel) is to not store a (doc,pos) tuple on disk, but to store positions, accompanied by a stream of doc/pos relationship bits: 1 means this position belongs to the next document, 0 means this position belongs to the current document. This is an easy way of saving some space without modifying the TurboPFor on-disk format: the posrel technique reduces the index size to about . With the increase in size, the Linux page cache hit ratio will be lower for the positional index, i.e. more data will need to be fetched from disk for querying the index. As long as the disk can deliver data as fast as you can decompress posting lists, this only translates into one disk seek s worth of additional latency. This is the case with modern NVMe disks that deliver thousands of MB/s, e.g. the Samsung 960 Pro (used in Hetzner s aforementioned EX61-NVME server). The values were measured by running dcs du -h /srv/dcs/shard*/full without and with the -pos argument.

Bytes read A positional index requires fewer queries: reading only the first and last trigram s posting lists and positions is sufficient to achieve a lower (!) false positive rate than evaluating all trigram s posting lists in a non-positional index. As a consequence, fewer files need to be read, resulting in fewer bytes required to read from disk overall. As an additional bonus, in a positional index, more data is read sequentially (index), which is faster than random i/o, regardless of the underlying disk.

1.2G

19.8G

21.0G regexp queries

4.2G (index)

10.8G (files)

15.0G identifier queries The values were measured by running iostat -d 25 just before running bench.zsh on an otherwise idle system.

Query speed Even though the positional index is larger and requires more data to be read at query time (see above), thanks to the C TurboPFor library, the 2 queries on a positional index are roughly as fast as the n queries on a non-positional index ( 4s instead of 3s). This is more than made up for by the combined i/o matching stage, which shrinks from 18.5s (7.1s i/o + 11.4s matching) to 1.3s.

3.3s (index)

7.1s (i/o)

11.4s (matching)

21.8s regexp queries

3.92s (index)

1.3s

5.22s identifier queries Note that identifier query i/o was sped up not just by needing to read fewer bytes, but also by only having to verify bytes at a known offset instead of needing to locate the identifier within the file.

Conclusion The new index format is overall slightly more efficient. This disk space efficiency allows us to introduce a positional index section for the first time. Most Debian Code Search queries are positional queries (78.2%) and will be answered much quicker by leveraging the positions. Bottomline, it is beneficial to use a positional index on disk over a non-positional index in RAM.

Arnab Goswami This particular gentleman is a class apart. He is the editor as well as Republic TV, a right-leaning channel which demonizes the minority, women whatever is antithesis to the Central Govt. of India. As a result there have been a spate of cases against him in the past few months. But surprisingly, in each of them he got hearing the day after the suit was filed. This is unique in Indian legal history so much so that a popular legal site which publishes on-going cases put up a post sharing how he was getting prompt hearings. That post itself needs to be updated as there have been 3 more hearings which have been done back to back for him. This is unusual as there have been so many cases pending for the SC attention, some arguably more important than this gentleman . So many precedents have been set which will send a wrong message. The biggest one, that even though a trial is taking place in the sessions court (below High Court) the SC can interject on matters. What this will do to the morale of both lawyers as well as judges of the various Sessions Court is a matter of speculation and yet as shared unprecedented. The saddest part was when Justice Chandrachud said

Justice Chandrachud If you don t like a channel then don t watch it. 11th November 2020 .

This is basically giving a free rope to hate speech. How can a SC say like that ? And this is the Same Supreme Court which could not take two tweets from Shri Prashant Bhushan when he made remarks against the judiciary .

J&K pleas in Supreme Court pending since August 2019 (Abrogation 370) After abrogation of 370, citizens of Jammu and Kashmir, the population of which is 13.6 million people including 4 million Hindus have been stuck with reduced rights and their land being taken away due to new laws. Many of the Hindus which regionally are a minority now rue the fact that they supported the abrogation of 370A . Imagine, a whole state whose answers and prayers have not been heard by the Supreme Court and the people need to move a prayer stating the same.

100 Journalists, activists languishing in Jail without even a hearing 55 Journalists alone have been threatened, booked and in jail for reporting of pandemic . Their fault, they were bring the irregularities, corruption made during the pandemic early months. Activists such as Sudha Bharadwaj, who giving up her American citizenship and settling to fight for tribals is in jail for 2 years without any charges. There are many like her, There are several more petitions lying in the Supreme Court, for e.g. Varavara Rao, not a single hearing from last couple of years, even though he has taken part in so many national movements including the emergency as well as part-responsible for creation of Telengana state out of Andhra Pradesh .

Then there is Devangana kalita who works for gender rights. Similar to Sudha Bharadwaj, she had an opportunity to go to UK and settle here. She did her master s and came back. And now she is in jail for the things that she studied. While she took part in Anti-CAA sittings, none of her speeches were incendiary but she still is locked up under UAPA (Unlawful Practises Act) . I could go on and on but at the moment these should suffice.

Petitions for Hate Speech which resulted in riots in Delhi are pending, Citizen s Amendment Act (controversial) no hearings till date. All of the best has been explained in a newspaper article which articulates perhaps all that I wanted to articulate and more. It is and was amazing to see how in certain cases Article 32 is valid and in many it is not. Also a fair reading of Justice Bobde s article tells you a lot how the SC is functioning. I would like to point out that barandbench along with livelawindia makes it easier for never non-lawyers and public to know how arguments are done in court, what evidences are taken as well as give some clue about judicial orders and judgements. Both of these resources are providing an invaluable service and more often than not, free of charge.

Student Suicide and High Cost of Education
For quite sometime now, the cost of education has been shooting up. While I have visited this topic earlier as well, recently a young girl committed suicide because she was unable to pay the fees as well as additional costs due to pandemic. Further investigations show that this is the case with many of the students who are unable to buy laptops. Now while one could think it is limited to one college then it would be wrong. It is almost across all India and this will continue for months and years. People do know that the pandemic is going to last a significant time and it would be a long time before R value becomes zero . Even the promising vaccine from Pfizer need constant refrigeration which is sort of next to impossible in India. It is going to make things very costly.

Last Nail on Indian Media Just today the last nail on India has been put. Thankfully Freedom Gazette India did a much better job so just pasting that

Information and Broadcasting Ministry bringing OTT services as well as news within its ambit.

With this, projects like Scam 1992, The Harshad Mehta Story or Bad Boy Billionaires:India, Test Case, Delhi Crime, Laakhon Mein Ek etc. etc. such kind of series, investigative journalism would be still-births. Many of these web-series also shared tales of woman empowerment while at the same time showed some of the hard choices that women had to contend to live with. Even western media may be censored where it finds the political discourse not to its liking. There had been so many accounts of Mr. Ravish Kumar, the winner of Ramon Magsaysay, how in his shows the electricity was cut in many places. I too have been the victim when the BJP governed in Maharashtra as almost all Puneities experienced it. Light would go for just half or 45 minutes at the exact time. There is another aspect to it. The U.S. elections showed how independent media was able to counter Mr. Trump s various falsehoods and give rise to alternative ideas which lead the team of Bernie Sanders, Joe Biden and Kamala Harris, Biden now being the President-elect while Kamala Harris being the vice-president elect. Although the journey to the white house seems as tough as before. Let s see what happens. Hopefully 2021 will bring in some good news. Update On 27th November 2020 Martin who runs the planet got an e-mail/notice by a Mr. Nikhil Sethi who runs the wikibio.com property. Mr. Sethi asked to remove the link pointing Devangana Kalita from my blog post to his site as he has used the no follow link. On inquiring further, the gentleman stated that it is an Updated mandate (his exact quote) from Google algorithm. To further understand the issue, I went to SERP as they are one of the more known ones on the subject. I also looked it up on Google as well. Found that the gentleman was BSing the whole time. The page basically talks about weightage of a page/site and authoritativeness which is known and yet highly contested ideas. In any case, the point for me was for whatever reason (could be fear, could be something else entirely), Mr. Sethi did not want me to link the content. Hence, I have complied above. I could have dragged it out but I do not wish Mr. Sethi any ill-being or/and further harm unduly and unintentionally caused by me. Hence, have taken down the link.

• Abhijith PA did 16.0h (out of 14h assigned and 2h from September).
• Adrian Bunk did 7h (out of 20.75h assigned and 5.75h from September), thus carrying over 19.5h to November.
• Ben Hutchings did 11.5h (out of 6.25h assigned and 9.75h from September), thus carrying over 4.5h to November.
• Brian May did 10h (out of 10h assigned).
• Chris Lamb did 18h (out of 18h assigned).
• Emilio Pozuelo Monfort did 20.75h (out of 20.75h assigned).
• Holger Levsen did 7.0h coordinating/managing the LTS team.
• Markus Koschany did 20.75h (out of 20.75h assigned).
• Mike Gabriel gave back the 8h he was assigned. See below
• Ola Lundqvist did 10.5h (out of 8h assigned and 2.5h from September).
• Roberto C. S nchez did 13.5h (out of 20.75h assigned) and gave back 7.25h to the pool.
• Sylvain Beucler did 20.75h (out of 20.75h assigned).
• Thorsten Alteholz did 20.75h (out of 20.75h assigned).
• Utkarsh Gupta did 20.75h (out of 20.75h assigned).

• Platinum sponsors:
• TOSHIBA (for 62 months)
• GitHub (for 52 months)
• Civil Infrastructure Platform (CIP) (for 30 months)
• Gold sponsors:
• Blablacar (for 77 months)
• Roche Diagnostics International AG (for 73 months)
• Linode (for 67 months)
• Babiel GmbH (for 56 months)
• Plat Home (for 55 months)
• University of Oxford (for 12 months)
• Silver sponsors:
• The Positive Internet Company (for 78 months)
• Domeneshop AS (for 77 months)
• Nantes M tropole (for 71 months)
• Univention GmbH (for 63 months)
• Universit Jean Monnet de St Etienne (for 63 months)
• Ribbon Communications, Inc. (for 57 months)
• Exonet B.V. (for 46 months)
• Leibniz Rechenzentrum (for 40 months)
• CINECA (for 30 months)
• Minist re de l Europe et des Affaires trang res (for 24 months)
• Cloudways Ltd (for 13 months)
• Dinahosting SL (for 11 months)
• Platform.sh (for 6 months)
• Bauer Xcel Media Deutschland KG (for 5 months)
• Bronze sponsors:
• Seznam.cz, a.s. (for 78 months)
• Evolix (for 77 months)
• Linuxhotel GmbH (for 75 months)
• Intevation GmbH (for 74 months)
• Daevel SARL (for 73 months)
• Bitfolk LTD (for 72 months)
• Megaspace Internet Services GmbH (for 72 months)
• Greenbone Networks GmbH (for 71 months)
• NUMLOG (for 71 months)
• WinGo AG (for 70 months)
• Ecole Centrale de Nantes LHEEA (for 66 months)
• Entr ouvert (for 62 months)
• Adfinis AG (for 59 months)
• Tesorion (for 54 months)
• GNI MEDIA (for 53 months)
• Laboratoire LEGI UMR 5519 / CNRS (for 53 months)
• Bearstech (for 45 months)
• LiHAS (for 45 months)
• People Doc (for 41 months)
• Catalyst IT Ltd (for 39 months)
• Supagro (for 35 months)
• Demarcq SAS (for 33 months)
• Universit Grenoble Alpes (for 19 months)
• TouchWeb SAS (for 11 months)
• SPiN AG (for 8 months)
• CoreFiling (for 4 months)

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Changes in RcppArmadillo version 0.10.1.2.0 (2020-11-15)

• Upgraded to Armadillo release 10.1.2 (Orchid Ambush)
• Remove three unused int constants (#313)
• Include main armadillo header using quotes instead of brackets
• Rewrite version number use in old-school mode because gcc 4.8.5
• Skipping parts of sparse conversion on Windows as win-builder fails

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.

Changes in tidyCpp version 0.0.2 (2020-11-12)

• Expanded definitions in internals.h to support new example.
• The vignette has been extended with an example based on package uchardet.
• Class Shield has been replaced by an new class Protect; a compatibility typdef has been added.
• The examples and vignette have been clarified with respect to proper ownership of protected objects; a new vignette section was added.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.

Welcome to the October 2020 report from the Reproducible Builds project. In our monthly reports, we outline the major things that we have been up to over the past month. As a brief reminder, the motivation behind the Reproducible Builds effort is to ensure flaws have not been introduced in the binaries we install on our systems. If you are interested in contributing to the project, please visit our main website.

General On Saturday 10th October, Morten Linderud gave a talk at Arch Conf Online 2020 on The State of Reproducible Builds in Arch. The video should be available later this month, but as a teaser:

The previous year has seen great progress in Arch Linux to get reproducible builds in the hands of the users and developers. In this talk we will explore the current tooling that allows users to reproduce packages, the rebuilder software that has been written to check packages and the current issues in this space.

During the Reproducible Builds summit in Marrakesh in 2019, developers from the GNU Guix, NixOS and Debian distributions were able to produce a bit-for-bit identical GNU Mes binary despite using three different versions of GCC. Since this summit, additional work resulted in a bit-for-bit identical Mes binary using tcc, and last month a fuller update was posted to this effect by the individuals involved. This month, however, David Wheeler updated his extensive page on Fully Countering Trusting Trust through Diverse Double-Compiling, remarking that:

GNU Mes rebuild is definitely an application of [Diverse Double-Compiling]. [..] This is an awesome application of DDC, and I believe it s the first publicly acknowledged use of DDC on a binary

There was a small, followup discussion on our mailing list. In openSUSE, Bernhard M. Wiedemann published his monthly Reproducible Builds status update. This month, the Reproducible Builds project restarted our IRC meetings, managing to convene twice: the first time on October 12th (summary & logs), and later on the 26th (logs). As mentioned in previous reports, due to the unprecedented events throughout 2020, there will be no in-person summit event this year. On our mailing list this month El as Alejandro posted a request for help with a local configuration

Debian-related work In August, Lucas Nussbaum performed an archive-wide rebuild of packages to test enabling the reproducible=+fixfilepath Debian build flag by default. Enabling this fixfilepath feature will likely fix reproducibility issues in an estimated 500-700 packages. However, this month Vagrant Cascadian posted to the debian-devel mailing list:

It would be great to see the reproducible=+fixfilepath feature enabled by default in dpkg-buildflags, and we would like to proceed forward with this soon unless we hear any major concerns or other outstanding issues. [ ] We would like to move forward with this change soon, so please raise any concerns or issues not covered already.

Debian Developer Stuart Prescott has been improving python-debian, a Python library that is used to parse Debian-specific files such as changelogs, .dscs, etc. In particular, Stuart is working on adding support for .buildinfo files used for recording reproducibility-related build metadata:

This can mostly be a very thin layer around the existing Deb822 types, using the existing Changes code for the file listings, the existing PkgRelations code for the package listing and gpg_* functions for signature handling.

A total of 159 Debian packages were categorised, 69 had their categorisation updated, and 33 had their classification removed this month, adding to our knowledge about identified issues. As part of this, Chris Lamb identified and classified two new issues: build_path_captured_in_emacs_el_file and rollup_embeds_build_path.

Software development This month, we tried to fix a large number of currently-unreproducible packages, including:

• Bernhard M. Wiedemann:
  • go (version 1.15.3 has improved reproducibility over 1.14)
  • goxel (sort SCons-related filesystem ordering issue)
  • lal (rework an old date-related patch)
  • lalmetaio (date)
  • libsemigroups (build failure in single-CPU mode)
  • memcached (build failure in 2025 due to expired SSL certificate)
  • octant (SUSE-specific date issue)
  • openmpi4 (date-related problem, revive old patch)
  • sbcl (datetime and hostname issue)
  • selinux-policy/policycoreutils (date-related issue in timezone)
• Chris Lamb:
  • #970383 filed against evince (forwarded upstream).
  • #971527 filed against libsass-python (forwarded upstream).
  • #972077 filed against pitivi.
  • #972078 filed against sound-juicer.
  • #972147 filed against pcbasic.
  • #972336 filed against ora2pg (forwarded upstream).
  • #972378 filed against fckit.
  • #972493 filed against gita.
  • #972494 filed against libgrokj2k.
  • #972496 filed against softether-vpn.
  • #972559 filed against perl.
  • #972561 filed against ruby-appraiser.
  • #972562 filed against gmerlin-avdecoder.
  • #972631 filed against node-proxy.
  • #972668 filed against yard.
  • #972861 filed against emacs.
  • #972930 filed against netcdf-parallel.
  • #965255 re-opened with new patch dh-fortran-mod.

Bernhard M. Wiedemann also reported three issues against bison, ibus and postgresql12.

Tools diffoscope is our in-depth and content-aware diff utility. Not only could you locate and diagnose reproducibility issues, it provides human-readable diffs of all kinds too. This month, Chris Lamb uploaded version 161 to Debian (later backported by Mattia Rizzolo), as well as made the following changes:

• Move test_ocaml to the assert_diff helper. [ ]
• Update tests to support OCaml version 4.11.1. Thanks to Sebastian Ramacher for the report. (#972518)
• Bump minimum version of the Black source code formatter to 20.8b1. (#972518)

In addition, Jean-Romain Garnier temporarily updated the dependency on radare2 to ensure our test pipelines continue to work [ ], and for the GNU Guix distribution Vagrant Cascadian diffoscope to version 161 [ ]. In related development, trydiffoscope is the web-based version of diffoscope. This month, Chris Lamb made the following changes:

• Mark a --help-only test as being a superficial test. (#971506)
• Add a real, albeit flaky, test that interacts with the try.diffoscope.org service. [ ]
• Bump debhelper compatibility level to 13 [ ] and bump Standards-Version to 4.5.0 [ ].

Lastly, disorderfs version 0.5.10-2 was uploaded to Debian unstable by Holger Levsen, which enabled security hardening via DEB_BUILD_MAINT_OPTIONS [ ] and dropped debian/disorderfs.lintian-overrides [ ].

Website and documentation This month, a number of updates to the main Reproducible Builds website and related documentation were made by Chris Lamb:

• Add a citation link to the academic article regarding dettrace [ ], and added yet another supply-chain security attack publication [ ].
• Reformatted the Jekyll s Liquid templating language and CSS formatting to be consistent [ ] as well as expand a number of tab characters [ ].
• Used relative_url to fix missing translation icon on various pages. [ ]
• Published two announcement blog posts regarding the restarting of our IRC meetings. [ ][ ]
• Added an explicit note regarding the lack of an in-person summit in 2020 to our events page. [ ]

Testing framework The Reproducible Builds project operates a Jenkins-based testing framework that powers tests.reproducible-builds.org. This month, Holger Levsen made the following changes:

• Debian-related changes:
  • Refactor and improve the Debian dashboard. [ ][ ][ ]
  • Track bugs which are usertagged as filesystem , fixfilepath , etc.. [ ][ ][ ]
  • Make a number of changes to package index pages. [ ][ ][ ]
• System health checks:
  • Relax disk space warning levels. [ ]
  • Specifically detect build failures reported by dpkg-buildpackage. [ ]
  • Fix a regular expression to detect outdated package sets. [ ]
  • Detect Lintian issues in diffoscope. [ ]

• Misc:
  • Make a number of updates to reflect that our sponsor Profitbricks has renamed itself to IONOS. [ ][ ][ ][ ]
  • Run a F-Droid maintenance routine twice a month to utilise its cleanup features. [ ]
  • Fix the target name in OpenWrt builds to ath79 from ath97. [ ]
  • Add a missing Postfix configuration for a node. [ ]
  • Temporarily disable Arch Linux builds until a core node is back. [ ]
  • Make a number of changes to our thanks page. [ ][ ][ ]

Build node maintenance was performed by both Holger Levsen [ ][ ] and Vagrant Cascadian [ ][ ][ ], Vagrant Cascadian also updated the page listing the variations made when testing to reflect changes for in build paths [ ] and Hans-Christoph Steiner made a number of changes for F-Droid, the free software app repository for Android devices, including:

• Do not fail reproducibility jobs when their cleanup tasks fail. [ ]
• Skip libvirt-related sudo command if we are not actually running libvirt. [ ]
• Use direct URLs in order to eliminate a useless HTTP redirect. [ ]

---

If you are interested in contributing to the Reproducible Builds project, please visit the Contribute page on our website. However, you can also get in touch with us via:

• IRC: #reproducible-builds on irc.oftc.net.
• Mailing list: rb-general@lists.reproducible-builds.org
• Social media: @ReproBuilds, @reproducible_builds@fosstodon.org & Reddit

Ingredients I am building on the these components:

• nix

Without the nix build system and package manger I probably woudn t even attempt to pull of complex tasks that may, say, require a patched ghc. For many years I resisted learning about nix, but when I eventually had to, I didn t want to go back.

• haskell.nix

This project provides an alternative Haskell build infrastructure for nix. While this is not crucial for tttool, it helps that they tend to have some cross-compilation-related patches more than the official nixpkgs. I also like that it more closely follows the cabal build work-flow, where cabal calculates a build plan based on your projects dependencies. It even has decent documentation (which is a new thing compared to two years ago).

• niv

Niv is a neat little tool to keep track of your dependencies. You can quickly update them with, say niv update nixpkgs. But what s really great is to temporarily replace one of your dependencies with a local checkout, e.g. via NIV_OVERRIDE_haskellNix=$HOME/build/haskell/haskell.nix nix-instantiate -A osx-exe-bundle There is a Github action that will keep your niv-managed dependencies up-to-date.

• Cachix.org

This service (proprietary, but free to public stuff up to 10GB) gives your project its own nix cache. This means that build artifacts can be cached between CI builds or even build steps, and your contributors. A cache like this is a must if you want to use nix in more interesting ways where you may end up using, say, a changed GHC compiler. Comes with GitHub actions integration.

• CI via Github actions

Until recently, I was using Travis, but Github actions are just a tad easier to set up and, maybe more important here, the job times are high enough that you can rebuild GHC if you have to, and even if your build gets canceled or times out, cleanup CI steps still happen, so that any new nix build products will still reach your nix cache.

The repository setup All files discussed in the following are reflected at https://github.com/entropia/tip-toi-reveng/tree/7020cde7da103a5c33f1918f3bf59835cbc25b0c. We are starting with a fairly normal Haskell project, with a single .cabal file (but multi-package projects should work just fine). To make things more interesting, I also have a cabal.project which configures one dependency to be fetched via git from a specific fork. To start building the nix infrastructure, we can initialize niv and configure it to use the haskell.nix repo:

niv init
niv add input-output-hk/haskell.nix -n haskellNix

This creates nix/sources.json (which you can also edit by hand) and nix/sources.nix (which you can treat like a black box). Now we can start writing the all-important default.nix file, which defines almost everything of interest here. I will just go through it line by line, and explain what I am doing here.

  checkMaterialization ? false  :

This defines a flag that we can later set when using nix-build, by passing --arg checkMaterialization true, and which is off by default. I ll get to that flag later.

let
  sources = import nix/sources.nix;
  haskellNix = import sources.haskellNix  ;

This imports the sources as defined niv/sources.json, and loads the pinned revision of the haskell.nix repository.

  # windows crossbuilding with ghc-8.10 needs at least 20.09.
  # A peek at https://github.com/input-output-hk/haskell.nix/blob/master/ci.nix can help
  nixpkgsSrc = haskellNix.sources.nixpkgs-2009;
  nixpkgsArgs = haskellNix.nixpkgsArgs;
  pkgs = import nixpkgsSrc nixpkgsArgs;

Now we can define pkgs, which is our version of the nixpkgs package set, extended with the haskell.nix machinery. We rely on haskell.nix to pin of a suitable revision of the nixpkgs set (see how we are using their niv setup). Here we could our own configuration, overlays, etc to nixpkgsArgs. In fact, we do in

  pkgs-osx = import nixpkgsSrc (nixpkgsArgs //   system = "x86_64-darwin";  );

to get the nixpkgs package set of an OSX machine.

  # a nicer filterSource
  sourceByRegex =
    src: regexes: builtins.filterSource (path: type:
      let relPath = pkgs.lib.removePrefix (toString src + "/") (toString path); in
      let match = builtins.match (pkgs.lib.strings.concatStringsSep " " regexes); in
      ( type == "directory"  && match (relPath + "/") != null
        match relPath != null)) src;

Next I define a little helper that I have been copying between projects, and which allows me to define the input to a nix derivation (i.e. a nix build job) with a set of regexes. I ll use that soon.

  tttool-exe = pkgs: sha256:
    (pkgs.haskell-nix.cabalProject  

The cabalProject function takes a cabal project and turns it into a nix project, running cabal v2-configure under the hood to let cabal figure out a suitable build plan. Since we want to have multiple variants of the tttool, this is so far just a function of two arguments pkgs and sha256, which will be explained in a bit.

      src = sourceByRegex ./. [
          "cabal.project"
          "src/"
          "src/.*/"
          "src/.*.hs"
          ".*.cabal"
          "LICENSE"
        ];

The cabalProject function wants to know the source of the Haskell projects. There are different ways of specifying this; in this case I went for a simple whitelist approach. Note that cabal.project.freze (which exists in the directory) is not included.

      # Pinning the input to the constraint solver
      compiler-nix-name = "ghc8102";

The cabal solver doesn t find out which version of ghc to use, that is still my choice. I am using GHC-8.10.2 here. It may require a bit of experimentation to see which version works for your project, especially when cross-compiling to odd targets.

      index-state = "2020-11-08T00:00:00Z";

I want the build to be deterministic, and not let cabal suddenly pick different package versions just because something got uploaded. Therefore I specify which snapshot of the Hackage package index it should consider.

      plan-sha256 = sha256;
      inherit checkMaterialization;

Here we use the second parameter, but I ll defer the explanation for a bit.

      modules = [ 
        # smaller files
        packages.tttool.dontStrip = false;
       ] ++

These modules are essentially configuration data that is merged in a structural way. Here we say that we want the tttool binary to be stripped (saves a few megabyte).

      pkgs.lib.optional pkgs.hostPlatform.isMusl  
        packages.tttool.configureFlags = [ "--ghc-option=-static" ];

Also, when we are building on the musl platform, that s when we want to produce a static build, so let s pass -static to GHC. This seems to be enough in terms of flags to produce static binaries. It helps that my project is using mostly pure Haskell libraries; if you link against C libraries you might have to jump through additional hoops to get static linking going. The haskell.nix documentation has a section on static building with some flags to cargo-cult.

        # terminfo is disabled on musl by haskell.nix, but still the flag
        # is set in the package plan, so override this
        packages.haskeline.flags.terminfo = false;
       ;

This (again only used when the platform is musl) seems to be necessary to workaround what might be a big in haskell.nix.

     ).tttool.components.exes.tttool;

The cabalProject function returns a data structure with all Haskell packages of the project, and for each package the different components (libraries, tests, benchmarks and of course executables). We only care about the tttool executable, so let s project that out.

  osx-bundler = pkgs: tttool:
   pkgs.stdenv.mkDerivation  
      name = "tttool-bundle";
      buildInputs = [ pkgs.macdylibbundler ];
      builder = pkgs.writeScript "tttool-osx-bundler.sh" ''
        source $ pkgs.stdenv /setup
        mkdir -p $out/bin/osx
        cp $ tttool /bin/tttool $out/bin/osx
        chmod u+w $out/bin/osx/tttool
        dylibbundler \
          -b \
          -x $out/bin/osx/tttool \
          -d $out/bin/osx \
          -p '@executable_path' \
          -i /usr/lib/system \
          -i $ pkgs.darwin.Libsystem /lib
      '';
     ;

This function, only to be used on OSX, takes a fully build tttool, finds all the system libraries it is linking against, and copies them next to the executable, using the nice macdylibbundler. This way we can get a self-contained executable. A nix expert will notice that this probably should be written with pkgs.runCommandNoCC, but then dylibbundler fails because it lacks otool. This should work eventually, though.

in rec  
  linux-exe      = tttool-exe pkgs
     "0rnn4q0gx670nzb5zp7xpj7kmgqjmxcj2zjl9jqqz8czzlbgzmkh";
  windows-exe    = tttool-exe pkgs.pkgsCross.mingwW64
     "01js5rp6y29m7aif6bsb0qplkh2az0l15nkrrb6m3rz7jrrbcckh";
  static-exe     = tttool-exe pkgs.pkgsCross.musl64
     "0gbkyg8max4mhzzsm9yihsp8n73zw86m3pwvlw8170c75p3vbadv";
  osx-exe        = tttool-exe pkgs-osx
     "0rnn4q0gx670nzb5zp7xpj7kmgqjmxcj2zjl9jqqz8czzlbgzmkh";

Time to create the four versions of tttool. In each case we use the tttool-exe function from above, passing the package set (pkgs, ) and a SHA256 hash. The package set is either the normal one, or it is one of those configured for cross compilation, building either for Windows or for Linux using musl, or it is the OSX package set that we instantiated earlier. The SHA256 hash describes the result of the cabal plan calculation that happens as part of cabalProject. By noting down the expected result, nix can skip that calculation, or fetch it from the nix cache etc. How do we know what number to put there, and when to change it? That s when the --arg checkMaterialization true flag comes into play: When that is set, cabalProject will not blindly trust these hashes, but rather re-calculate them, and tell you when they need to be updated. We ll make sure that CI checks them.

  osx-exe-bundle = osx-bundler pkgs-osx osx-exe;

For OSX, I then run the output through osx-bundler defined above, to make it independent of any library paths in /nix/store. This is already good enough to build the tool for the various systems! The rest of the the file is related to packaging up the binaries, to tests, and various other things, but nothing too essentially. So if you got bored, you can more or less stop now.

  static-files = sourceByRegex ./. [
    "README.md"
    "Changelog.md"
    "oid-decoder.html"
    "example/.*"
    "Debug.yaml"
    "templates/"
    "templates/.*\.md"
    "templates/.*\.yaml"
    "Audio/"
    "Audio/digits/"
    "Audio/digits/.*\.ogg"
  ];
  contrib = ./contrib;

The final zip file that I want to serve to my users contains a bunch of files from throughout my repository; I collect them here.

  book =  ;

The project comes with documentation in the form of a Sphinx project, which we build here. I ll omit the details, because they are not relevant for this post (but of course you can peek if you are curious).

  os-switch = pkgs.writeScript "tttool-os-switch.sh" ''
    #!/usr/bin/env bash
    case "$OSTYPE" in
      linux*)   exec "$(dirname "''$ BASH_SOURCE[0] ")/linux/tttool" "$@" ;;
      darwin*)  exec "$(dirname "''$ BASH_SOURCE[0] ")/osx/tttool" "$@" ;;
      msys*)    exec "$(dirname "''$ BASH_SOURCE[0] ")/tttool.exe" "$@" ;;
      cygwin*)  exec "$(dirname "''$ BASH_SOURCE[0] ")/tttool.exe" "$@" ;;
      *)        echo "unsupported operating system $OSTYPE" ;;
    esac
  '';

The zipfile should provide a tttool command that works on all systems. To that end, I implement a simple platform switch using bash. I use pks.writeScript so that I can include that file directly in default.nix, but it would have been equally reasonable to just save it into nix/tttool-os-switch.sh and include it from there.

  release = pkgs.runCommandNoCC "tttool-release"  
    buildInputs = [ pkgs.perl ];
    ''
    # check version
    version=$($ static-exe /bin/tttool --help perl -ne 'print $1 if /tttool-(.*) -- The swiss army knife/')
    doc_version=$(perl -ne "print \$1 if /VERSION: '(.*)'/" $ book /book.html/_static/documentation_options.js)
    if [ "$version" != "$doc_version" ]
    then
      echo "Mismatch between tttool version \"$version\" and book version \"$doc_version\""
      exit 1
    fi

Now the derivation that builds the content of the release zip file. First I double check that the version number in the code and in the documentation matches. Note how $ static-exe refers to a path with the built static Linux build, and $ book the output of the book building process.

    mkdir -p $out/
    cp -vsr $ static-files /* $out
    mkdir $out/linux
    cp -vs $ static-exe /bin/tttool $out/linux
    cp -vs $ windows-exe /bin/* $out/
    mkdir $out/osx
    cp -vsr $ osx-exe-bundle /bin/osx/* $out/osx
    cp -vs $ os-switch  $out/tttool
    mkdir $out/contrib
    cp -vsr $ contrib /* $out/contrib/
    cp -vsr $ book /* $out
  '';

The rest of the release script just copies files from various build outputs that we have defined so far. Note that this is using both static-exe (built on Linux) and osx-exe-bundle (built on Mac)! This means you can only build the release if you either have setup a remote osx builder (a pretty nifty feature of nix, which I unfortunately can t use, since I don't have access to a Mac), or the build product must be available in a nix cache (which it is in my case, as I will explain later). The output of this derivation is a directory with all the files I want to put in the release.

  release-zip = pkgs.runCommandNoCC "tttool-release.zip"  
    buildInputs = with pkgs; [ perl zip ];
    ''
    version=$(bash $ release /tttool --help perl -ne 'print $1 if /tttool-(.*) -- The swiss army knife/')
    base="tttool-$version"
    echo "Zipping tttool version $version"
    mkdir -p $out/$base
    cd $out
    cp -r $ release /* $base/
    chmod u+w -R $base
    zip -r $base.zip $base
    rm -rf $base
  '';

And now these files are zipped up. Note that this automatically determines the right directory name and basename for the zipfile. This concludes the step necessary for a release.

  gme-downloads =  ;
  tests =  ;

These two definitions in default.nix are related to some simple testing, and again not relevant for this post.

  cabal-freeze = pkgs.stdenv.mkDerivation  
    name = "cabal-freeze";
    src = linux-exe.src;
    buildInputs = [ pkgs.cabal-install linux-exe.env ];
    buildPhase = ''
      mkdir .cabal
      touch .cabal/config
      rm cabal.project # so that cabal new-freeze does not try to use HPDF via git
      HOME=$PWD cabal new-freeze --offline --enable-tests   true
    '';
    installPhase = ''
      mkdir -p $out
      echo "-- Run nix-shell -A check-cabal-freeze to update this file" > $out/cabal.project.freeze
      cat cabal.project.freeze >> $out/cabal.project.freeze
    '';
   ;

Above I mentioned that I still would like to be able to just run cabal, and ideally it should take the same library versions that the nix-based build does. But pinning the version of ghc in cabal.project is not sufficient, I also need to pin the precise versions of the dependencies. This is best done with a cabal.project.freeze file. The above derivation runs cabal new-freeze in the environment set up by haskell.nix and grabs the resulting cabal.project.freeze. With this I can run nix-build -A cabal-freeze and fetch the file from result/cabal.project.freeze and add it to the repository.

  check-cabal-freeze = pkgs.runCommandNoCC "check-cabal-freeze"  
      nativeBuildInputs = [ pkgs.diffutils ];
      expected = cabal-freeze + /cabal.project.freeze;
      actual = ./cabal.project.freeze;
      cmd = "nix-shell -A check-cabal-freeze";
      shellHook = ''
        dest=$ toString ./cabal.project.freeze 
        rm -f $dest
        cp -v $expected $dest
        chmod u-w $dest
        exit 0
      '';
      ''
      diff -r -U 3 $actual $expected  
          echo "To update, please run"; echo "nix-shell -A check-cabal-freeze"; exit 1;  
      touch $out
    '';

But generated files in repositories are bad, so if that cannot be avoided, at least I want a CI job that checks if they are up to date. This job does that. What s more, it is set up so that if I run nix-shell -A check-cabal-freeze it will update the file in the repository automatically, which is much more convenient than manually copying. Lately, I have been using this pattern regularly when adding generated files to a repository: * Create one nix derivation that creates the files * Create a second derivation that compares the output of that derivation against the file in the repo * Create a derivation that, when run in nix-shell, updates that file. Sometimes that derivation is its own file (so that I can just run nix-shell nix/generate.nix), or it is merged into one of the other two. This concludes the tour of default.nix.

The CI setup The next interesting bit is the file .github/workflows/build.yml, which tells Github Actions what to do:

name: "Build and package"
on:
  pull_request:
  push:

Standard prelude: Run the jobs in this file upon all pushes to the repository, and also on all pull requests. Annoying downside: If you open a PR within your repository, everything gets built twice. Oh well.

jobs:
  build:
    strategy:
      fail-fast: false
      matrix:
        include:
        - target: linux-exe
          os: ubuntu-latest
        - target: windows-exe
          os: ubuntu-latest
        - target: static-exe
          os: ubuntu-latest
        - target: osx-exe-bundle
          os: macos-latest
    runs-on: $  matrix.os  

The build job is a matrix job, i.e. there are four variants, one for each of the different tttool builds, together with an indication of what kind of machine to run this on.

    - uses: actions/checkout@v2
    - uses: cachix/install-nix-action@v12

We begin by checking out the code and installing nix via the install-nix-action.

    - name: "Cachix: tttool"
      uses: cachix/cachix-action@v7
      with:
        name: tttool
        signingKey: '$  secrets.CACHIX_SIGNING_KEY  '

Then we configure our Cachix cache. This means that this job will use build products from the cache if possible, and it will also push new builds to the cache. This requires a secret key, which you get when setting up your Cachix cache. See the nix and Cachix tutorial for good instructions.

    - run: nix-build --arg checkMaterialization true -A $  matrix.target  

Now we can actually run the build. We set checkMaterialization to true so that CI will tell us if we need to update these hashes.

    # work around https://github.com/actions/upload-artifact/issues/92
    - run: cp -RvL result upload
    - uses: actions/upload-artifact@v2
      with:
        name: tttool ($  matrix.target  )
        path: upload/

For convenient access to build products, e.g. from pull requests, we store them as Github artifacts. They can then be downloaded from Github s CI status page.

  test:
    runs-on: ubuntu-latest
    needs: build
    steps:
    - uses: actions/checkout@v2
    - uses: cachix/install-nix-action@v12
    - name: "Cachix: tttool"
      uses: cachix/cachix-action@v7
      with:
        name: tttool
        signingKey: '$  secrets.CACHIX_SIGNING_KEY  '
    - run: nix-build -A tests

The next job repeats the setup, but now runs the tests. Because of needs: build it will not start before the builds job has completed. This also means that it should get the actual tttool executable to test from our nix cache.

  check-cabal-freeze:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v2
    - uses: cachix/install-nix-action@v12
    - name: "Cachix: tttool"
      uses: cachix/cachix-action@v7
      with:
        name: tttool
        signingKey: '$  secrets.CACHIX_SIGNING_KEY  '
    - run: nix-build -A check-cabal-freeze

The same, but now running the check-cabal-freeze test mentioned above. Quite annoying to repeat the setup instructions for each job

  package:
    runs-on: ubuntu-latest
    needs: build
    steps:
    - uses: actions/checkout@v2
    - uses: cachix/install-nix-action@v12
    - name: "Cachix: tttool"
      uses: cachix/cachix-action@v7
      with:
        name: tttool
        signingKey: '$  secrets.CACHIX_SIGNING_KEY  '
    - run: nix-build -A release-zip
    - run: unzip -d upload ./result/*.zip
    - uses: actions/upload-artifact@v2
      with:
        name: Release zip file
        path: upload

Finally, with the same setup, but slightly different artifact upload, we build the release zip file. Again, we wait for build to finish so that the built programs are in the nix cache. This is especially important since this runs on linux, so it cannot build the OSX binary and has to rely on the cache. Note that we don t need to checkMaterialization again. Annoyingly, the upload-artifact action insists on zipping the files you hand to it. A zip file that contains just a zipfile is kinda annoying, so I unpack the zipfile here before uploading the contents.

Conclusion With this setup, when I do a release of tttool, I just bump the version numbers, wait for CI to finish building, run nix-build -A release-zip and upload result/tttool-n.m.zip. A single file that works on all target platforms. I have not yet automated making the actual release, but with one release per year this is fine. Also, when trying out a new feature, I can easily create a branch or PR for that and grab the build products from Github s CI, or ask people to try them out (e.g. to see if they fixed their bugs). Note, though, that you have to sign into Github before being able to download these artifacts. One might think that this is a fairly hairy setup finding the right combinations of various repertories so that cross-compilation works as intended. But thanks to nix s value propositions, this does work! The setup presented here was a remake of a setup I did two years ago, with a much less mature haskell.nix. Back then, I committed a fair number of generated files to git, and juggled more complex files but once it worked, it kept working for two years. I was indeed insulated from upstream changes. I expect that this setup will also continue to work reliably, until I choose to upgrade it again. Hopefully, then things are even more simple, and require less work-around or manual intervention.

• [1] https://bugs.kde.org/show_bug.cgi?id=316348
• [2] https://tinyurl.com/y3veoyvw
• [3] https://tinyurl.com/y5tstthv
• [4] https://tinyurl.com/hqcmzdb
• [5] https://www.youtube.com/watch?v=zT64Q9kuj2c
• [6] https://tinyurl.com/y3kwy5zp
• [7] https://tinyurl.com/y6ypvy26
• [8] https://tinyurl.com/y4jo3q39
• [9] https://tinyurl.com/yyna9z7y
• [10] https://tinyurl.com/y3xzayea
• [11] https://tinyurl.com/y4hv8mxm
• [12] https://tinyurl.com/y5rhmqlz

deb https://download.opensuse.org/repositories/home:/npreining:/debian-kde:/frameworks/Debian_Unstable/ ./
deb https://download.opensuse.org/repositories/home:/npreining:/debian-kde:/plasma520/Debian_Unstable/ ./
deb https://download.opensuse.org/repositories/home:/npreining:/debian-kde:/apps2008/Debian_Unstable/ ./
deb https://download.opensuse.org/repositories/home:/npreining:/debian-kde:/other/Debian_Unstable/ ./

• Update will need two trials because files moved from plasma-desktop to plasma-workspace. I will add the required replace/conflicts later.
• Make sure that kwayland-server packages (libkwaylandserver5, libkwaylandserver-dev are at version 5.20.2. Some old versions had an epoch so automatic updates will not work.

• Don't create negative cost for lot without cost
• Support complex implicit conversions
• Handle typed metadata with value 0 correctly
• Set per-unit instead of total cost when cost is missing from lot
• Support commodity-less amounts
• Convert transactions with no amounts or only 0 amounts to notes
• Fix parsing of transaction notes
• Keep tags in transaction notes on same line as transaction header
• Add beancount config options for non-standard root names automatically
• Fix conversion of fixated prices to costs
• Fix removal of price when price==cost but when they use different number formats
• Fix removal of price when price==cost but per-unit and total notation mixed
• Fix detection of tags and metadata after posting/aux date
• Use D directive to set default commodity for hledger
• Improve support for postings with commodity-less amounts
• Allow empty comments
• Preserve leading whitespace in comments in postings and transaction headers
• Preserve indentation for tags and metadata
• Preserve whitespace between amount and comment
• Refactor code to use more data structures
• Remove dependency on Config::Onion module

Tseng Labs ET4000AX (1989) This SVGA graphics card was installed into a PC powered by a 386SX CPU running at 16 MHz. This was a good card at the time as it was pretty fast. It didn t feature 2D acceleration, unlike the later ET4000/W32. This version only features 512 KB of RAM. It can display 1024 768 images with 16 colors or 800 600 with 256 colors. It was also compatible with CGA, EGA, VGA, MDA, and Hercules modes. No contemporary games were using the SVGA modes but the higher resolutions were useful with Windows 3. This card was manufactured directly by Tseng Labs.

Tseng Labs ET4000 AX ISA card

AdLib clone (1992) My first sound card was an AdLib. My parents bought it in Canada during the summer holidays in 1992. It uses a Yamaha OPL2 chip to produce sound via FM synthesis. The first game I have tried is Indiana Jones and the Last Crusade. I think I gave this AdLib to a friend once I upgraded my PC with a Sound Blaster Pro 2. Recently, I needed one for a side project, but they are rare and expensive on eBay. Someone mentioned a cheap clone on Vogons, so I bought it. It was sold by Sun Moon Star in 1992 and shipped with a CD-ROM of Doom shareware.

AdLib clone ISA card by Sun Moon Star

On this topic, take a look at OPL2LPT: an AdLib sound card for the parallel port and OPL2 Audio Board: an AdLib sound card for Arduino .

Sound Blaster Pro 2 (1992) Later, I switched the AdLib sound card with a Sound Blaster Pro 2. It features an OPL3 chip and was also able to output digital samples. At the time, this was a welcome addition, but not as important as the FM synthesis introduced earlier by the AdLib.

Sound Blaster Pro 2 ISA card

Promise EIDE 2300 Plus (1995) I bought this card mostly for the serial port. I was using a 486DX2 running at 66 MHz with a Creatix LC 288 FC external modem. The serial port was driven by an 8250 UART with no buffer. Thanks to Terminate, I was able to connect to BBSes with DOS, but this was not possible with Windows 3 or OS/2. I needed one of these fancy new cards with a 16550 UART, featuring a 16-byte buffer. At the time, this was quite difficult to find in France. During a holiday trip, I convinced my parent to make a short detour from Los Angeles to San Diego to buy this Promise EIDE 2300 Plus controller card at a shop I located through an advertisement in a local magazine! The card also features an EIDE controller with multi-word DMA mode 2 support. In contrast with the older PIO modes, the CPU didn t have to copy data from disk to memory.

Promise EIDE 2300 Plus VLB card

3dfx Voodoo2 Magic 3D II (1998) The 3dfx Voodoo2 was one of the first add-in graphics cards implementing hardware acceleration of 3D graphics. I bought it from a friend along with his Pentium II box in 1999. It was a big evolutionary step in PC gaming, as games became more beautiful and fluid. A traditional video controller was still required for 2D. A pass-through VGA cable daisy-chained the video controller to the Voodoo, which was itself connected to the monitor.

3dfx Voodoo2 Magic 3D II PCI card

3Com 3C905C-TX-M Tornado (1999) In the early 2000s, in college, the Internet connection on the campus was provided by a student association through a 100 Mbps Ethernet cable. If you wanted to reach the maximum speed, the 3Com 3C905C-TX-M PCI network adapter, nicknamed Tornado , was the card you needed. We would buy it second-hand by the dozen and sell them to other students for around 30 .

3Com 3C905C-TX-M PCI card