| 21 Nov 2025 |
 raitobezarius | Unnamed pairs | 21:08:07 |
 Sergei Zimmerman (xokdvium) | I did research a bit the distribution of list sizes when evaling nixpkgs. Small lists are quite often used, but lists just pale in comparison with attrsets overall | 21:17:12 |
 mzero | name value pairs are so common because of listToAttrs, etc, I wonder if a pair type would actually make a significant perf difference | 21:19:00 |
| Sergei Zimmerman (xokdvium) | A more generic approach could be to have "attrset shapes". Very similar to how v8 optimizes classes with the same layout | 21:20:09 |
| Sergei Zimmerman (xokdvium) | Then names wouldn't need to be stored in the attribute set and function calls could reuse the same memory and not copy anything to a new Env.
(I and Robert Hensing discussed this a bit at some point) | 21:21:57 |
 Qyriad | In reply to @xokdvium:matrix.org
A more generic approach could be to have "attrset shapes". Very similar to how v8 optimizes classes with the same layout benefits of a JIT especially | 21:22:04 |
| Sergei Zimmerman (xokdvium) | Not exactly tho. jit/memory layout are tangential somewhat | 21:22:32 |
| Qyriad | yeah but you can optimize hot shapes | 21:22:56 |
| Sergei Zimmerman (xokdvium) | Yeah. I think python has slots for this kind of thing | 21:23:13 |
| Sergei Zimmerman (xokdvium) | * Yeah. I think python has __slots__ for this kind of thing | 21:23:28 |
| mzero | do you have something I could read about that? I'm curious how it would work. | 21:25:02 |
| Sergei Zimmerman (xokdvium) | Probably staring at prior art in V8? I haven't done that myself, but I'd be curious how they do tracing to find hot shapes | 21:26:04 |
| Sergei Zimmerman (xokdvium) | All of those optimizations are pretty inaccessible without tracing infra :( | 21:27:26 |
| Sergei Zimmerman (xokdvium) | But tracing attrset shapes doesn't exactly depend on function call tracing. Computing a shape fingerprint and having a small hashmap of that could give a rough picture of the frequency. | 21:29:23 |
| Sergei Zimmerman (xokdvium) | So maybe only do this for attrsets smaller than N, compute a hash of symbol table ids, store it a fixed-sized map and count frequency that way. This shouldn't have much of an overhead | 21:30:50 |
 John Ericson | yeah that is in a bitrotted PR | 21:39:29 |
| 16 May 2024 |
|  zrsk joined the room. | 13:54:49 |
 samrose | In reply to @lunaphied:lunaphied.me
I think there were a few CLs on the Gerrit but nothing being actively worked The other thing that I could do if it helps is test things and try to find bugs. I did do some C++ work in the past, but may lack the time to do it justice here at least for about 30 days or so | 15:55:29 |
| Qyriad | we are not in any rush 🙂 | 17:20:53 |
| samrose | Would it help to also test out the existing Lix code and try to find issues/bugs etc? | 17:23:21 |
| Qyriad | absolutely | 17:23:41 |
| samrose |
- how do people feel about the existing test suite that comes along with nix source code or Lix?
| 17:23:48 |
| Qyriad | it's pitiful | 17:24:10 |
| samrose | heh | 17:24:16 |
| raitobezarius | expanding it is cool | 17:24:23 |
| raitobezarius | writing new tests for builtins which are not tested | 17:24:30 |
| raitobezarius | new test behaviors, etc. | 17:24:32 |
| Qyriad | we have three flavors of test:
gtest (offer only available in libexpr and libutil) bash script virtual machine
the vast, vast majority of testing is in the "bash script" flavor and it is a mess | 17:25:01 |
| samrose | I was just going to ask on the "functional" tests: do we still like using bash there? | 17:25:56 |
| samrose | the last time that I worked on a major nix related cli project that used bash, or bats for testing, over time it became rather kind of hard to maintain | 17:26:42 |
