tavianator

5 ms·

1.
by tavianator 3mo ago
Didn't Google have a tool for this called MOE (Make Open Easy) like 15 years ago? I remember it from some of my open source contributions to Guice
2.
by tavianator 6mo ago
> Airplanes don't have wings ???
3.
by tavianator 8mo ago
No: https://en.wikipedia.org/wiki/Sony_Computer_Entertainment_Am...
4.
by tavianator 11mo ago
Presumably that's just a mistake. The author calls it "stochastic gradient descent" correctly elsewhere in the article
5.
There is no memory safety without thread safety(ralfj.de)
456 points by tavianator 1y ago|503 comments
6.
by tavianator 1y ago
I did try it a while ago and it wasn't profitable, but that was before I added stat() support. Batching those is probably good
7.
by tavianator 1y ago
My bfs project also uses io_uring: https://github.com/tavianator/bfs/blob/main/src/ioq.c I'm curious how lsr compares to bfs -ls for example. bfs only uses io_uring when multiple threads are e
8.
by tavianator 1y ago
You may want to look into improvements to A* for grids, like Rectangular Symmetry Reduction.
9.
by tavianator 1y ago
> There was no other helix db https://en.wikipedia.org/wiki/Helix_(database)
10.
by tavianator 1y ago
They were referencing the title of a specific paper, which invented type classes: https://dl.acm.org/doi/10.1145/75277.75283
11.
by tavianator 1y ago
The C standard (since C99) says that `main()` has an implicit `return 0`, you don't need to write it explicitly.
12.
by tavianator 1y ago
I was looking for a relevant paper and found this one, which isn't what I was looking for but is related: https://sigops.org/s/conferences/hotos/2023/papers/liargkova...
13.
by tavianator 1y ago
My actual "production" implementation of this concept does support that: https://github.com/tavianator/bfs/blob/main/configure But I wanted the blog post sized version to be simpler for exposit
14.
by tavianator 1y ago
Just tried reconfiguring LLVM: 27.24s user 8.71s system 99% cpu 36.218 total Admittedly the LLVM build time dwarfs the configuration time, but still. If you're only building a smaller component then the config time dominates:
15.
by tavianator 1y ago
Fixed! https://github.com/tavianator/tavianator.com/commit/aa9d99d5...
16.
by tavianator 1y ago
Nice! I used to do something similar, don't remember exactly why I had to switch but the two step process did become necessary at some point. Just from a quick peek at that repo, nowadays you can write #if __has_attribute(cold) and av
17.
by tavianator 1y ago
Whoops! Forgot to do that when I switched from a ``` block to raw html
18.
by tavianator 1y ago
You might be interested in rawhide[1] or fselect[2]. (Note: I don't really use them myself, but they seem to offer something like what you're suggesting.) Also, this is still a find-style syntax, but my bfs utility supports -excl
19.
by tavianator 1y ago
At least with GNU coreutils, you can use `-r`/`--relative`
20.
by tavianator 1y ago
Someday I will get that functionality into fd :)
21.
by tavianator 2y ago
I've replaced Valgrind with sanitizers for most of my workflow. Using the sanitizer APIs in your custom allocator is also easy: https://github.com/tavianator/bfs/blob/main/src/sanity.h https:
22.
by tavianator 2y ago
Very interesting, thanks! If I get time I'll try to measure every instruction to see the whole set of affected instructions.
23.
by tavianator 2y ago
Wrote up the presumed explanation here: https://tavianator.com/2025/shlxplained.html
24.
by tavianator 2y ago
In general I'd be very surprised if code alignment had much effect on a 10,000 instruction block, especially since the instruction is 5 bytes long so it will quickly unalign itself
25.
by tavianator 2y ago
> Wait a sec, isn’t this backwards? No, if you push and pop RCX it's fast again. I mentioned this in the blog post, `mov rcx, 1` is slow but `mov rcx, 1; push rcx; pop rcx` is fast.
26.
by tavianator 2y ago
Right. Actually it turns out it's 11 bits, since [-1024, 1023] are all supported by the immediate add renamer. In general I think people are overstating the delay of an additional 64-bit add on register file reads (though I'm not
27.
by tavianator 2y ago
Benchmark code is in the post! The trick is to limit the number of SHLX instructions before you re-initialize RCX. Doing it every 10,000 keeps it fresh enough. I didn't have to disable preemption or anything, perf shows 0 context sw
28.
by tavianator 2y ago
I did try aligning the loop, it didn't matter
29.
by tavianator 2y ago
SAL and SHL are synonyms, they have the same encoding. SHL only accepts CL as the count register, there's no other form that takes a variable shift count
30.
by tavianator 2y ago
SHL suffers from the same latency issue as SHLX it turns out

More ›