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2022-10-11 r/5105 fix(tvix/eval/builtins): force acc not list element in foldl'sterni1-0/+2
When investigating discrepancies between foldl' in tvix and C++ Nix, I discovered that C++ Nix's foldl' doesn't seem to be strict at all. Since this seemed wrong, I looked into Haskell's foldl' implementation which doesn't force the list elements (`val` in our code), but the accumulation value (`res` in our code). You can look at the code here: https://hackage.haskell.org/package/base-4.17.0.0/docs/src/GHC.List.html#foldl%27 This actually makes a lot of sense: If `res` is not forced after each application of `op`, we'll end up thunks nested as deeply as the list is long, potentially taking up a lot of space. This can be limited by forcing the `res` thunk before applying `op` again (and creating a new thunk). I've also PR-ed an equivalent change for C++ Nix at https://github.com/NixOS/nix/pull/7158. Since this is not merged nor backported to our Nix 2.3 fork, I've not copied the eval fail test yet, since it wouldn't when checking our tests against C++ Nix in depot. Change-Id: I34edf6fc3031fc1485c3e714f2280b4fba8f004b Reviewed-on: https://cl.tvl.fyi/c/depot/+/6947 Autosubmit: sterni <sternenseemann@systemli.org> Reviewed-by: grfn <grfn@gws.fyi> Tested-by: BuildkiteCI
2022-10-01 r/5008 docs(tvix/eval): start doc about problematic/weird lang behaviorsterni1-0/+39
The idea is that we can keep track of the more unexpected behavior, behavior that maybe should not be a thing at all and behavior we are not sure about yet. Change-Id: I70933f00af1230a7ab9d30e917b61199fe571caf Reviewed-on: https://cl.tvl.fyi/c/depot/+/6803 Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
2022-09-18 r/4896 docs(tvix/eval): note C++ implementation details for C++ Nixsterni1-0/+8
Just want to note those down somewhere before I forget them again, we can delete them later if we have it all figured out. Change-Id: Icafa2d8fc7ca39e38e9637b7eca6f2bbf487c2b8 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6632 Autosubmit: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI Reviewed-by: tazjin <tazjin@tvl.su>
2022-09-11 r/4821 docs(tvix/eval): propose builtin "inlining" optimisationsterni1-0/+18
Change-Id: I96a187792a1fd48cffd6b56ec22347aee8cae3af Reviewed-on: https://cl.tvl.fyi/c/depot/+/6526 Autosubmit: sterni <sternenseemann@systemli.org> Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
2022-09-11 r/4820 docs(tvix/eval): mention `?` and `or` for builtins optimisationsterni1-1/+3
Change-Id: Ifaa6da345d408a69ce46d6a0e7483352715c75bd Reviewed-on: https://cl.tvl.fyi/c/depot/+/6525 Autosubmit: sterni <sternenseemann@systemli.org> Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
2022-09-11 r/4804 docs(tvix/eval): add some notes on recursive attribute setsVincent Ambo1-0/+60
Change-Id: I36b826f12854a22e60a27ed1982ab5528c58bdad Reviewed-on: https://cl.tvl.fyi/c/depot/+/6489 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-11 r/4803 docs(tvix/eval): add optimisation note on eliminating `with` thunksVincent Ambo1-6/+9
Change-Id: I18d50ac8e157929a027f8bf284e65f1eb8950d5a Reviewed-on: https://cl.tvl.fyi/c/depot/+/6488 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-08 r/4748 refactor(tvix/eval): return call frame result from VM::callVincent Ambo1-0/+16
Previously, "calling" (setting up the VM run loop for executing a call frame) and "running" (running this loop to completion) were separate operations. This was basically an attempt to avoid nesting `VM::run` invocations. However, doing things this way introduced some tricky bugs for exiting out of the call frames of thunks vs. builtins & closures. For now, we unify the two operations and always return the value to the caller directly. For now this makes calls a little less effective, but it gives us a chance to nail down some other strange behaviours and then re-optimise this afterwards. To make sure we tackle this again further down I've added it to the list of known possible optimisations. Change-Id: I96828ab6a628136e0bac1bf03555faa4e6b74ece Reviewed-on: https://cl.tvl.fyi/c/depot/+/6415 Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-09-08 r/4746 docs(tvix/eval): add notes for builtins access optimisationVincent Ambo1-0/+10
Change-Id: Iadbfbe2864ae42fe5492ef3ede0925baee4872b2 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6413 Reviewed-by: sterni <sternenseemann@systemli.org> Tested-by: BuildkiteCI
2022-09-06 r/4652 docs(tvix/eval): start a document on known optimisation potentialVincent Ambo1-0/+57
Change-Id: I9bc41e57e1cfdf536d7b9048bac2e7aff1ee2ffa Reviewed-on: https://cl.tvl.fyi/c/depot/+/6313 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-09-04 r/4648 docs(tvix/eval): pad pure column so it can fit "false"sterni1-107/+107
Change-Id: Iaedfc281db82de1e8eb2400db1118c8431d2579f Reviewed-on: https://cl.tvl.fyi/c/depot/+/6333 Tested-by: BuildkiteCI Autosubmit: sterni <sternenseemann@systemli.org> Reviewed-by: tazjin <tazjin@tvl.su>
2022-09-04 r/4647 docs(tvix/eval): add a list of builtins added in Nix >= 2.4sterni1-0/+11
`builtins.getFlake` doesn't interest us, of course, but some others may be worth (or easy) to implement. They are pretty low priority, though, since nixpkgs has compatiblity wrappers for the ones it uses. The new debugging-related builtins (break and traceVerbose) are interesting to note, but may not make sense to implement at all. Change-Id: Icae547aa3bd9d6ee6b87897ba8210eb9b9b044c7 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6332 Tested-by: BuildkiteCI Autosubmit: sterni <sternenseemann@systemli.org> Reviewed-by: tazjin <tazjin@tvl.su>
2022-09-02 r/4586 docs(tvix/eval): add an overview of all builtins in NixVincent Ambo1-0/+120
Change-Id: Ie187f3317046c6c9e59852d4a128f25ceed99309 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6252 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
2022-08-13 r/4428 docs(tvix/eval): add design documentation for attrset opcodesVincent Ambo1-0/+122
Change-Id: I303b57e035543f4597c6247983d1d533e4014638 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6092 Tested-by: BuildkiteCI Reviewed-by: grfn <grfn@gws.fyi>