John Regehr

he/him

Public Key

npub15xjwk4qzx56p5tdsmzsge7m5ahztkp4nzmrmkw2cp324t888rwsswe5a5k

NIP-05 Address

regehr_at_mastodon.social@mostr.pub

Profile Code

nprofile1qqs2rf8t2spr2dq69kcd3gyvld6wm39mq6e3d3am89vqc424nnn3hggpz4mhxue69uhhyetvv9ujumt0wd68ytnsw43qz9thwden5te0v35hgar09ec82c30wfjkcctec60whh

Publishing to

relay.mostr.pub

ditto.pub/relay

relay.noswhere.com

Author Public Key

npub15xjwk4qzx56p5tdsmzsge7m5ahztkp4nzmrmkw2cp324t888rwsswe5a5k

Show more details

Last Notes

2024-09-07 21:52:14

anyone know what this stuff is? some sort of medicine? It was in the liquor cabinet of a friend who passed away
https://files.mastodon.social/media_attachments/files/113/098/484/605/294/375/original/646c5bc350db4fd1.mp4

2024-08-29 22:49:04

reading Watts' _Blindsight_. it's definitely my jam, not sure why it never made it to the top of my list before now

2024-08-18 23:12:34

some sort of leech has attached itself
alt: just a flat tabbycat glued to my midsection
https://files.mastodon.social/media_attachments/files/112/985/552/319/777/584/original/ccb747b6244aada4.jpeg

2024-08-18 02:11:32

honestly these potato chips are a little bit confusing
alt: crispy taco flavored Lays
https://files.mastodon.social/media_attachments/files/112/980/592/962/743/337/original/5340f3f513c205c7.jpeg

2024-08-04 04:01:43

- reply

@npub14fs…qegk jfc

2024-08-03 20:18:01

pretty cool paper about superoptimizing assembly code
https://eprint.iacr.org/2022/1303.pdf

2024-08-03 16:53:13

it warms my heart to see everyone dogpiling on Piers Anthony
https://www.reddit.com/r/BestofRedditorUpdates/comments/1eiu1jg/my_25f_recent_boyfriend_37m_gave_me_a_book_to/

2024-07-30 18:09:25

- reply

@npub1sys…ckr3 hahahah nice. but yeah I know either, I just appreciate CMM as a way to understand how serious an org is at producing quality software on a predictable schedule

2024-07-30 02:40:17

- reply

@npub1src…fms4 I should watch it again! I went through it as it came out but never really approached it as a complete thing

2024-07-30 02:37:46

- reply

@npub1src…fms4 the German time travel show?

2024-07-29 16:59:15

it's been a while since I taught Advanced Compilers and this time I thought I'd start out having the class read a few big-picture papers about the field.
some ideas I had include:
- Reflections on Trusting Trust
- Impact of economics on compiler optimization
- Death of Optimizing Compilers
https://cr.yp.to/talks/2015.04.16/slides-djb-20150416-4x3.pdf
what else should be on this list?

2024-07-29 01:17:57

- reply

@npub14fs…qegk I don’t think that one really exists

2024-07-29 00:56:30

- reply

@npub14fs…qegk no need to assume, with that mf

2024-07-24 14:33:43

- reply

@npub1src…fms4 ❤️

2024-07-24 02:55:34

the Rolling Stones finished a tour two days ago, and it turns out neither Mick Jagger nor Keith Richards is a boomer -- they were born in 1943.
and also, this standup bit about Keith's apparent immortality is from *1990*:
https://www.youtube.com/watch?v=1ln54geqGks

2024-07-20 19:49:23

you just know that when this happened there was someone at Crowdstrike who said "so what are we doing to prevent this from happening on Windows" at a meeting and everyone was like "Bob SHUT UP"
https://www.neowin.net/news/crowdstrike-broke-debian-and-rocky-linux-months-ago-but-no-one-noticed/

2024-07-19 15:39:21

I often tell people that security software is sort of uniquely horrible since it runs at maximum privilege level while being developed by B- or C- software shops. today isn't a counterexample.

2024-07-14 23:59:34

- reply

@npub1src…fms4 thanks Miguel!

2024-07-14 22:40:11

my wife isn’t on this site but as of today we’ve been married for 23 years! ❤️ ❤️ ❤️

2024-07-12 21:19:40

this beer is balanced but overly complicated
alt: beer can labeled AVL IPA
https://files.mastodon.social/media_attachments/files/112/775/601/821/346/182/original/a7e4e8c5c908c86c.jpeg

2024-07-09 01:30:29

"I was rejected because I told my interviewer I never make mistakes"
this is so good:
https://www.reddit.com/r/BORUpdates/comments/1dynufe/excuse_me_miss_im_a_professional_i_was_rejected/

2024-07-07 00:07:11

I want to send out props to my wont-be-named colleague who just now sent an email with the main body of "Agree with John." and then 3 separate, lengthy, footnotes

2024-07-05 16:42:19

why are we assuming malloc can't fail?
https://gcc.godbolt.org/z/d4rs4hfGE

2024-07-04 23:59:23

ideally, a compiler would be monotonic in the sense that giving it more information would never make it generate worse code. these folks go looking for violations of this principle in GCC and LLVM.
https://dl.acm.org/doi/pdf/10.1145/3656404

2024-07-03 16:59:42

even if you had a bad day at work, at least you didn't try to static-fire a rocket and it got loose
https://www.space.com/space-pioneer-tianlong-3-rocket-accidental-launch

2024-06-27 18:13:44

The SIGPLAN Programming Languages Software Award goes to the original Rust team!!!!!
https://files.mastodon.social/media_attachments/files/112/689/936/159/396/099/original/3f1f1b4f73d43bef.jpeg

2024-06-17 02:45:39

someone turn out the lights, astrophysics is done https://en.wikipedia.org/wiki/Nuclear_pasta
https://files.mastodon.social/media_attachments/files/112/629/665/156/356/394/original/0239863d266da6f1.png

2024-05-26 17:05:55

- reply

@npub14fs…qegk I don’t have a problem on the input side but my students and I all constantly type the wrong one of these

2024-05-25 23:42:55

- reply

@npub1src…fms4 "let us never speak of this again"

2024-05-25 17:57:25

just a peephole optimization in the Go compiler bailing out if c+d != c+d, where c and d are FP constants
(must be a NaN check, but they have an isNaN call available, so why obfuscate it this way?)
https://files.mastodon.social/media_attachments/files/112/503/010/407/690/132/original/a56d3e7a1cbc4bf5.png

2024-05-21 23:11:43

- reply

@npub1a4c…t2kf if "it's worth reacting, it's worth over-reacting."
but for real: I'm sure you've seen the Microsoft AI bullshit that just dropped?

2024-05-21 22:10:12

I saw "orange roughy" at the supermarket and immediately thought this must be one of those fish they renamed so that people would want to eat them and yep
https://files.mastodon.social/media_attachments/files/112/481/361/667/012/863/original/280146ecea022974.png

2024-05-17 15:16:27

yesterday I talked to someone who has two proposals in the system at the US NSF and both got rated Highly Competitive, which usually means a grant will get funded, and both are getting rejected due to the dire budget situation there. not good!
https://www.insidehighered.com/news/government/science-research-policy/2024/05/02/researchers-shocked-and-disappointed-after-nsf

2024-05-17 00:04:21

- reply

@npub1src…fms4 love to see them fly and be free :)

2024-05-16 23:32:14

I totally forgot to take a photo, but my PhD student Manasij Muhkerjee just successfully defended his thesis "Peephole Optimizations : From Craft towards Science"!!!@!1!!!!!

2024-05-13 00:33:00

my parents have some beekeeper neighbors and a colony escaped and found a home at my folks’ mailbox!!!
https://files.mastodon.social/media_attachments/files/112/430/961/850/565/990/original/78a582efee863286.jpeg

2024-05-10 03:00:47

alt: golden hour on the central Wasatch Range over some burbs
https://files.mastodon.social/media_attachments/files/112/414/557/225/254/339/original/d0c1b6c66c948d1b.jpeg

2024-05-09 15:16:27

a Panera bread opened up not far from where I live. actually not, I bet Apple Maps scraped a database a bit too aggressively -- probably the people who live there own a franchise
https://files.mastodon.social/media_attachments/files/112/411/780/854/674/092/original/62601c69cd1414fe.png

2024-05-05 21:11:42

great that we bought some patio furniture on Friday!
https://files.mastodon.social/media_attachments/files/112/390/534/518/894/380/original/9c4d952e6c251282.jpeg

2024-05-04 20:13:53

- reply

@npub14fs…qegk better keep them coming I've read all those :)

2024-05-04 20:04:25

last few years, when I have a slow weekend I like to read a graphic novel. one that I've really enjoyed is Yokohama Kaidashi Kikou. if I had to be there at the end of the world, this is how I would want it to be.
https://www.amazon.com/dp/B0B5GC3GMF/

2024-05-04 02:32:30

- reply

@npub1y0e…mm9n implementing AVL trees from Knuth's MIX is a significant challenge

2024-05-03 21:30:07

"He mispronounced quite common words: urticate, salpinx, bordereau."

2024-05-03 18:05:23

I've been seeing more posts recently about AIs getting poisoned by training on AI bullshit, but this reminds me of the time I assigned students to go find a red-black tree implementation on the web and then test it and fix the bugs they found. most of the available implementations were so wrong that the assignment was infeasible, and this was well before the current wave of AI-generated bullshit.

2024-04-27 21:14:40

did y'all know that "fdupes" is like *really* slow when you point it at an 85 GB directory tree? all I'm asking for here is good algorithmics

2024-04-24 22:47:41

- reply

@npub1c9m…9xjd there are definitely limits to what can be done in that format, but mostly I think that's part of the charm

2024-04-24 22:45:11

- reply

@npub1c9m…9xjd awesome!

2024-04-24 22:25:31

"Explaining Code using ASCII Art" was one of the most fun blog posts I ever wrote
https://blog.regehr.org/archives/1653
and now there's a paper on this topic! ❤️
https://pg.ucsd.edu/publications/how-programmers-ASCII-diagram-code_CHI-2024.pdf

2024-04-21 16:13:04

- reply

@npub1c9m…9xjd most of these seem tractable during the next 50 years or so, but not printing, we should just leave that one alone

2024-04-19 19:31:46

this has to be one of my all-time favorite bug-finding techniques: in your widely deployed software, at very low probability, you put a new heap allocation next to a protected page. performance is unaffected and the bugs that you find are those that actually matter to users in practice.
https://arxiv.org/pdf/2311.09394v2.pdf

2024-04-16 17:41:33

"The legal rule that computers are presumed to be operating correctly – unforeseen and unjust consequences"
https://www.benthamsgaze.org/wp-content/uploads/2022/06/briefing-presumption-that-computers-are-reliable.pdf
a lot to unpack here!

2024-04-09 17:49:51

TIL that in IEEE FP, -0.0 + +0.0 = +0.0
https://alive2.llvm.org/ce/z/jPi8ZV

2024-03-31 20:38:19

oh no!! Mathematical Recreations and Computer Recreations were staples of my childhood and adolescent years, such amazing material
https://lfpress.remembering.ca/obituary/alexander-dewdney-1089463499

2024-03-30 22:10:22

is there a good survey paper sort of thing about real-world weaponized software backdoors / backdoor attempts, that covers stuff like the 2003 Linux one, the 2015 Juniper router one, etc.? seems like this is something that's deserving of real study

2024-03-29 23:21:09

- reply

@npub14fs…qegk agreed. it'll be interesting to see how this plays out. and to whoever did it, fuck them and I hope they look like assholes forever, to the internet

2024-03-29 22:43:13

- reply

@npub14fs…qegk but also how stupid would people have to be to not cover up stuff like names, time zones, etc?

2024-03-29 22:26:08

lots of talk today about open source supply chain vulnerabilities and obviously that is a very real problem, but I would think that's hard-mode.
if you have nation-state level resources, getting a few of your people in the door at FAANG companies seems way easier than this

2024-03-29 18:43:39

- reply

@npub1809…nd7t every internet user owes you a beer

2024-03-29 15:28:33

it's quite dated at this point but _Why Cryptosystems Fail_ is such a beautiful paper, fun to read and a complete antidote to the sorts of stuff we are (or were) taught about computer security in classes
https://www.cl.cam.ac.uk/~rja14/Papers/wcf.pdf

2024-03-28 23:52:21

"Xr0 Makes C Safer than Rust"
https://xr0.dev/safer

2024-03-25 02:34:44

the mountain is out tonight! and that moon is all ready to do its eclipse thing
https://files.mastodon.social/media_attachments/files/112/153/984/438/843/169/original/c76ce30e2982ef4a.jpeg

2024-03-20 15:30:57

- reply

@npub143w…pykj that's just its passive-aggressive way of protecting you from those pages

2024-03-15 22:48:38

I really hope nobody uses this site to do anything that violates their local laws but if you did for example require an electronic copy of a book that you totally own legally speaking then this site would be an awesome place to make this happen
https://libgen.is/

2024-03-15 22:35:30

I don't think anyone reads Dirk Gently anymore. but if they did they would understand both the problem and the solution.
https://www.reddit.com/r/therewasanattempt/comments/1bfndpi/to_move_a_couch/

2024-03-07 21:25:36

https://files.mastodon.social/media_attachments/files/112/056/513/200/359/561/original/3995cbe0a690a8b1.jpeg

2024-03-06 20:48:33

with the recent Dune interest, I have to remind everyone that this book exists
https://en.wikipedia.org/wiki/National_Lampoon%27s_Doon
I don't think anyone needs to go out of their way to find a copy, but it does have its moments. Herbert's writing style is a pretty easy target.

2024-03-05 22:29:30

- reply

@npub1pu3…8r76 @npub1c0z…9vx5 also I bet a trash can that's missing the lid

2024-03-05 21:53:25

here's a new paper about bridging the gap between discovering a missing compiler optimization (both humans and superoptimizers are good at this) and obtaining a correct and general implementation of that optimization in a production compiler (this is very hard, even for experts)
https://users.cs.utah.edu/~regehr/generalization-oopsla24.pdf
this is my student Manasij's thesis work. I'll just throw modesty to the wind and say that this is a really important paper for how we'll build compilers in the future!

2024-02-28 01:31:25

- reply

@npub1u3f…nne2 rough life!!

2024-02-24 21:21:33

- reply

@npub1a4c…t2kf I always enjoyed talking to Jon when I'd run into him! but it's been a while. he's no longer at Hopkins, do you know what he's up to?

2024-02-21 21:41:12

"it will be left to decompose naturally"
in Oregon, they'll never forget Nov 12 1970
https://files.mastodon.social/media_attachments/files/111/971/632/290/258/175/original/3b7beee2840f21ff.png

2024-02-20 23:12:29

one of my students who works on program synthesis is playing around with GPT-4 which is actually kind of a great use of AI -- we have an SMT solver to check everything it emits, we would never trust it for a millisecond otherwise
and also, our current synthesis strategy (enumeration) is so painfully boneheaded that even random-ass LLM magic seems like an improvement

2024-02-19 23:20:42

- reply

@npub1pu3…8r76 but it's ever better if there's as much time in between these two things as possible -- so they made the UI suck

2024-02-19 23:05:22

the programmers behind the Canvas LMS have managed to build very nasty races on top of what is almost certainly a transactional-database-backed web site. plenty of instructors have gotten burned by this; for years now, I've told my TAs: only one person edits Canvas grades at a time.
https://mastodon.social/@predrag@hachyderm.io/111960629537208842

2024-02-18 23:18:10

- reply

@npub1src…fms4 my guess is the LLVM interpreter is more trouble than it's worth and wasm sounds probably the way to go

2024-02-18 04:39:58

I wish more computer scientists would read books like this, they’re a great antidote to people who think formal verification is some sort of systems safety panacea
https://hachyderm.io/@cornazano/111947785095905083

2024-02-17 21:49:42

- reply

@npub1pu3…8r76 @npub1c0z…9vx5 a shame that Europe wimped out on metric time

2024-02-17 21:44:38

- reply

@npub1c0z…9vx5 @npub1pu3…8r76 I think Fabian is salty because we have beautiful base 2 fractions whereas his preferred system uses the awkward and artificial base 10

2024-02-16 23:28:58

greatest country on Earth, folks
https://files.mastodon.social/media_attachments/files/111/943/754/013/969/613/original/851f77cf8bc84bfb.png

2024-02-03 00:44:00

- reply

@npub1src…fms4 Please Don't Destroy is like the only funny thing about SNL now, as far as I can tell

2024-02-02 23:56:27

"nepo truce" is really strong, I'm 100% going to make this happen at a faculty meeting to call out everyone who has a parent that's an academic
https://www.youtube.com/watch?v=XX_Rxvg8vdo

2024-02-01 02:50:00

it's fun to see people in the USA fight argue about our food https://deadspin.com/the-great-american-menu-foods-of-the-states-ranked-an-1349137024

2024-01-26 03:11:22

- reply

@npub1src…fms4 at least you didn't log in and leave a comment. I hope.

2024-01-26 00:41:21

- reply

@npub1src…fms4 yes!!!

2024-01-26 00:34:16

- reply

@npub1src…fms4 other day I posted something snarky like this and like 12 people came and told me it's a maintenance issue not a Boeing issue. I wish you better luck with your own snark.

2024-01-24 16:33:35

at this point I'm thinking maybe just tighten *all* the bolts on these things
https://files.mastodon.social/media_attachments/files/111/811/885/038/545/828/original/c6c8ba90b2fa2061.png

2024-01-24 02:09:06

I would 100% read the book-length version of this https://www.abortretry.fail/p/the-itanic-saga

2024-01-23 03:10:01

question for LLVM / AArch64 people: where can I find out what this LLVM backend does for "fastcc" functions? is this written up? so far I've just implemented the calling convention from AAPCS64 in my translation validation tool

2024-01-22 23:22:33

- reply

@npub1a4c…t2kf I'm super out of touch with MS at this point, but who ever is their customer base these days? now that many people do without a home PC, is it like 96% corporate and government?

2024-01-22 04:04:16

- reply

@npub1a4c…t2kf whatever keeps these folks off the streets is fine with me!

2024-01-15 01:35:10

alt: snowy foothills and low storm clouds
https://files.mastodon.social/media_attachments/files/111/757/391/049/884/547/original/b25e42202a493da2.jpeg

2024-01-14 16:50:21

never seen an avalanche forecast like this 😬
https://files.mastodon.social/media_attachments/files/111/755/326/908/558/210/original/2e6116701d3151e5.png

2024-01-12 03:57:17

this is so good, the crypto example cast of characters
(via @npub153x…v0k6)
https://en.wikipedia.org/wiki/Alice_and_Bob#Cast_of_characters
https://files.mastodon.social/media_attachments/files/111/740/964/606/409/334/original/997eb461649b2424.png

2024-01-06 02:40:53

wikipedia has so many gems, but this has to be one of the best.
related, English is such a clusterfuck, what a crazy language
but also I'm completely obsessed with heteronyms, they're the best thing ever
https://files.mastodon.social/media_attachments/files/111/706/685/804/678/347/original/eee78f857aee53f0.png

2024-01-05 20:44:39

was just rereading a 2016 blog post about teaching C to undergrads and I think it has held up pretty well
https://blog.regehr.org/archives/1393

2024-01-02 04:31:29

if you're having trouble finding a book that's out of print or that your local library doesn't carry, Library Genesis is pretty amazing
https://libgen.is/

2023-12-30 01:21:42

- reply

@npub1a4c…t2kf I’m old enough to remember that American cars required frequent oil checks not incredibly long ago

2023-12-27 05:28:27

see, that wasn't that hard was it?
https://github.com/coq/ceps/blob/coq-roadmap/text/069-coq-roadmap.md#change-of-name-coq---the-rocq-prover
"The Coq developer team has validated the renaming of Coq into the Rocq Prover."

2023-12-23 22:41:56

"Memory Safety is a Red Herring"
https://steveklabnik.com/writing/memory-safety-is-a-red-herring
this is a very nice, nuanced piece, even if Steve went with a bit of a clickbaity title (or maybe it wasn't intended that way and I'm only reading it as clickbaity...)

2023-12-23 22:23:35

#caturday
https://files.mastodon.social/media_attachments/files/111/632/069/345/281/544/original/dd77a3bbfac90744.jpeg