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Jan Midtgaard

@janmidtgaard.bsky.social
70 followers 77 following 37 posts

Recovering academic. Occasionally hacks OCaml and property-based testing, manufacturing bad luck on an industrial scale. Mastodon account: types.pl/@jmid

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Jan Midtgaard @janmidtgaard.bsky.social · 23/09/2025
types.pl/@jmid/115253...
types.pl
Jan Midtgaard (@jmid@types.pl)
Here's a preprint of the paper I wrote up for Olivier's festscrift 🎉 🍾 Property-Based Testing of OCaml 5's Runtime System: Fun and Segfaults with Interpreters and State Transition Functions We desc...
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David Ho @davidho.bsky.social · 04/05/2025
I think a lot about what Carl Sagan said in one of his final interviews.
"WE'VE ARRANGED A society based on science and technology, in which nobody understands anything about science technology. And this combustible mixture of ignorance and power, sooner or later, is going to blow up in our faces. Who is running the science and technology in a democracy if the people don't know anything about it?"
"Science is more than a body of knowledge, it's a way of thinking. A way of skeptically interrogating the universe with a fine understanding of human fallibility. If we are not able to ask skeptical questions, to interrogate those who tell us that something is true, to be skeptical of those in authority, then we're up for grabs for the next charlatan, political or religious, who comes ambling along."
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Yaron Minsky @yminsky.bsky.social · 24/06/2025
A gem from Stephen Dolan, which proposes replacing the "generational hypothesis" that drives the design of generational GCs with a notion of lifetime dispersion as measured by the gini coefficient. Nice to see economics playing a role here! dl.acm.org/doi/pdf/10.1...
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Jan Midtgaard @janmidtgaard.bsky.social · 08/05/2025
Last night it was announced that our TACAS-paper 'Dynamic Verification of OCaml Software with Gospel and Ortac/QCheck-STM' co-authored with Nikolaus Huber, Naomi Spargo, Nicolas Osborne, and Samuel Hym won the 2025 @etapsconf.bsky.social's Best Tool Paper Award 🎉 #testing #pbt #award
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Noah Shachtman @noahshachtman.bsky.social · 07/05/2025
There are people I know in the national security community who are terrified that the US government is sleepwalking into a 9/11-level catastrophe. Focusing finite resources on nonsense like this instead of credible threats -- that is the reason they're so worried. www.wsj.com/world/greenl...
wsj.com
Exclusive | U.S. Orders Intelligence Agencies to Step Up Spying on Greenland
The push underscores the seriousness of President Trump’s intent to acquire the island from Denmark.
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Anil Madhavapeddy @anil.recoil.org · 06/05/2025
Oooh, MirageOS+unikraft PR has appeared from @tarides.com, which should allow much easier deployment of OCaml code to the @unikraft.cloud ! github.com/ocaml/opam-r...
github.com
Publish OCaml/Unikraft packages v1.0.0 by shym · Pull Request #27856 · ocaml/opam-repository
OCaml/Unikraft: an OCaml cross compiler to Unikraft backends OCaml/Unikraft is structured into many packages to allow users to build only what they need. Packages use one of two version numbers: 0...
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Martin Janiczek @janiczek.cz · 01/05/2025
A blogpost I wrote on elm-test's Test.Distribution - testing whether your fuzzers generate interesting cases often enough! martin.janiczek.cz/2025/05/01/e...
martin.janiczek.cz
Elm test distributions
…in which I’ll tell you how you can make sure your property based tests are testing the interesting cases.
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Gro-Tsen @gro-tsen.bsky.social · 07/04/2025
This video was posted on Twitter by the official account of the People's Republic of China's embassy in the United States. The Chinese Communist Party is lecturing the US Republican President by using a Reagan speech on the importance of free trade. We are really living in the Weird timeline.
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KC Sivaramakrishnan @kcsrk.info · 05/04/2025
👀 Oleg Kiselyov's compilers course in OCaml 👀 okmij.org/ftp/tagless-...
okmij.org
Compiler
The materials for the course on compilers: built incrementally and fully in tagless-final style
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Jan Midtgaard @janmidtgaard.bsky.social · 04/04/2025
...and the award for best exception name showing up in an opam-repo CI run goes to... 🏆😄
CI log error message that has a red cross and the text "pyml.20210924 (failed: Great)"
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Marcello Seri @mseri.me · 26/03/2025
≪We estimate the supply-side value of widely-used OSS is $4.15 billion, but that the demand-side value is much larger at $8.8 trillion. We find that firms would need to spend 3.5 times more on software than they currently do if OSS did not exist.≫ From www.hbs.edu/faculty/Page... #opensource
hbs.edu
The Value of Open Source Software - Working Paper - Faculty & Research - Harvard Business School
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New Nomads @new-nomads.com · 24/03/2025
Just... have... to drop this... here.
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Jan Midtgaard @janmidtgaard.bsky.social · 23/03/2025
Scratching another old itch, I've utilized a wonderful hack by @edwintorok.bsky.social to get the Thread-modes of Lin and STM working much better 🤓 github.com/ocaml-multic... (as in: from defunct to decent) It even works on OCaml 4 too! 😄
github.com
Improve context switching chance in `Lin_thread` and `STM_thread` modes by jmid · Pull Request #540 · ocaml-multicore/multicoretests
This fixes #338 - or at least gives it a good kick in the right direction. Both Lin_thread and STM_thread are currently marked as experimental - and for good reason: The chance of them triggering u...
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KC Sivaramakrishnan @kcsrk.info · 14/03/2025
If all goes well, OCaml 5 code will ride into space in < 24 hrs. www.dphispace.com/post/parsimo...
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Jan Midtgaard @janmidtgaard.bsky.social · 12/03/2025
> We have been using OCaml 5 in production since the middle of February 2025, and the rollout has been entirely uneventful. This was a highlight for me, after having worked to stress test it over the past ~3 years. There are other nuggets in @semgrep.bsky.social's latest blog post though... 🤓
semgrep.dev
Semgrep | Upgrading Semgrep from OCaml 4 to OCaml 5
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KC Sivaramakrishnan @kcsrk.info · 10/03/2025
Great work from @tarides.com folks on pragmatic verification of OCaml software. Chosen as one of the distinguished papers at TACAS 2025. Paper: janmidtgaard.dk/papers/Huber... Code: discuss.ocaml.org/t/ann-ortac-...
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David Allsopp @dra27.uk · 01/03/2025
Finally - Relocatable OCaml in “fully relocatable” mode is also reproducible (as long as the C compiler is reproducible) and passes its testsuite 😮‍💨🥳🎉🍾🎊
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Jan Midtgaard @janmidtgaard.bsky.social · 18/02/2025
Dear all After a bit over 3 years my contract with Tarides has come to an end. It has been great - working with and being team lead for an exceptional group of software engineers and - applying my property-based testing skills to stress test and help get the multicore OCaml5 runtime+stdlib in shape.
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Jan Midtgaard @janmidtgaard.bsky.social · 14/02/2025
Raphaël Monat has a PhD position open to work on static analysis with him at Inria in Lille 🙂 recrutement.inria.fr/public/class... #phd-position #abstract-interpretation #static-analysis #ocaml
recrutement.inria.fr
PhD Position F/M Resource-Aware Conservative Static Analysis
Offre d'emploi Inria
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Jan Midtgaard @janmidtgaard.bsky.social · 06/02/2025
Beautiful morning in Aarhus for a morning dip with 4C water and 3C air ☀️🌊🤓
A bright February sunrise over a point where the sea meets a slim sand beach with a forest of naked trees close by.
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Jan Midtgaard @janmidtgaard.bsky.social · 05/02/2025
QCheck(2) hacking continues: 💻 github.com/c-cube/qchec... Replacing an RNG split hack with faster, gastly Obj.magic one, QCheck2 on OCaml 4 starts to work reasonably 🤓 #ocaml #quickcheck #pbt
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ading.dev @ading.dev · 31/01/2025
I got Linux running in a PDF file using a RISC-V emulator. PDFs support Javascript, so Emscripten is used to compile the TinyEMU emulator to asm.js, which runs in the PDF. It boots in about 30 seconds and emulates a riscv32 buildroot system. linux.doompdf.dev/linux.pdf github.com/ading2210/li...
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Jan Midtgaard @janmidtgaard.bsky.social · 31/01/2025
Over the past couple of days, I've been scratching a 3-year old QCheck(2) itch github.com/c-cube/qchec... It's nice to finally make progress on it! 😃 #ocaml #quickcheck #pbt #fp
github.com
QCheck2 shrinker improvements to list, array, bytes, strings, and functions by jmid · Pull Request #319 · c-cube/qcheck
This PR takes a first step towards improving the QCheck2 list shrinker. The current one uses the input size tree and offers only prefixes, e.g., shrinking [1;2;3;4;5;6;7;8] to [], [1;2;3;4], [1;2;3...
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Brian Phillips @brianphillips.lol · 30/01/2025
If you wanted no leaks you should have gone into Settings -> Security -> Configure privacy & security -> Privacy options -> Other -> Configure -> Media interface and clicked “Disallow.” The Leak setting is on by default but we understand your privacy is important so we’ve made it easy to opt out
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Yaron Minsky @yminsky.bsky.social · 30/01/2025
A post about the long and winding road that lead to the Dune build system for OCaml, and, eventually, to Dune replacing our old internal build system, Jenga. blog.janestreet.com/how-we-accid...
blog.janestreet.com
How we accidentally built a better build system for OCaml
A “build system” is one of the most important tools in a developer’stoolbox. Roughly, it figures out how to create runnable programs froma bunch of different...
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Jan Midtgaard @janmidtgaard.bsky.social · 18/01/2025
Yesterday a very good friend gave me this nice box of homemade OCaml coasters, all 3d-printed. Naturally, they were immediately put to good use... 😄🍻 #ocaml #fp
A box with coasters, each with an OCaml-logo camel on them and lying on a white table
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xvw @xvw.lol · 17/01/2025
I'm really happy to present, with @tarides.com , #OCaml Eglot, an #Emacs (minor) mode for editing OCaml code, using LSP through Eglot, the built-in #LSP client of Emacs: github.com/tarides/ocam... Feedback, contribution and RT much appreciated
github.com
GitHub - tarides/ocaml-eglot: An overlay on Eglot for editing OCaml code using LSP
An overlay on Eglot for editing OCaml code using LSP - tarides/ocaml-eglot
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depths of wikipedia @depthsofwikipedia.bsky.social · 13/01/2025
this is the entire article
"no fly list" article on simple english wikipedia. has just three sentences and the last one is  "In the movie Alvin and the Chipmunks 4: The Road Chip, the Chipmunks get onto the No Fly List."
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Jan Midtgaard @janmidtgaard.bsky.social · 10/01/2025
TIL that multicoretests has entered Debian tracker.debian.org/pkg/ocaml-mu... and Arch('s user repo) aur.archlinux.org/packages/oca... 😮🎉 #ocaml #pbt #quickcheck #fp
tracker.debian.org
ocaml-multicoretests - Debian Package Tracker
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David Sancho @david.sancho.dev · 30/12/2024
Published a blog post about cram tests (fancy snapshot tests) in dune. It's a bit of a tutorial style and showcases a feature I truly like about dune. Hope you like it! sancho.dev/blog/cram-t...
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Jan Midtgaard @janmidtgaard.bsky.social · 24/12/2024
I've written up part 2 on our effort to utilize property-based testing to stress test the OCaml 5 run time system. Happy Christmas reading! 🎄🎅 🎁 😄 tarides.com/blog/2024-12... #ocaml #pbt #fp #functionalprogramming #quickcheck
tarides.com
Multicore Property-Based Tests for OCaml 5: Challenges and Lessons Learned
We summarise the challenges and lessons learned in developing a test suite of property-based tests to help ensure the correctness of OCaml 5.
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Jan Midtgaard @janmidtgaard.bsky.social · 20/12/2024
This week the story of the UK Horizon post office scandal hit the news in Denmark. It's a sad story of subtle software defects sending people to prison by a miscarriage of justice, loss of jobs and marriage, etc. 😬 (insert PBT/abs.int/verification pitch here) www.computerweekly.com/feature/Post...
computerweekly.com
Post Office Horizon scandal explained: Everything you need to know | Computer Weekly
Computer Weekly has investigated the Post Office Horizon scandal since 2008 and is, in fact, part of the story. This guide covers essential information about the scandal.
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