577772566b
The memoize function is not a pretty thing in terms of implementation, but it's exactly what we need to solve this UX problem and performance problem. Without this, every distinct `withSystem` call will cause a re-evaluation of the `perSystem` module, which is inefficient. Now, it's a one-time 13KB and length(system) attribute lookups: negligible compared to any instantiations and such. Nix doesn't offer memoization for functions yet, so this is the best we can do.
23 lines
771 B
Nix
23 lines
771 B
Nix
# Run with:
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# NIX_SHOW_STATS=1 nix eval --expr 'import ./measure-bytes-per-char.nix { control = false; size = 10; }' --impure
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# NIX_SHOW_STATS=1 nix eval --expr 'import ./measure-bytes-per-char.nix { control = true; size = 10; }' --impure
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{ control ? false, size ? 10 }:
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let
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lib = import <nixpkgs/lib>;
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inherit (import ./memoize.nix { inherit lib; }) memoizeStr;
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# Create a string of the specified size
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key = lib.concatStrings (lib.genList (i: "a") size);
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# Memoized identity function
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memoId = memoizeStr (x: x);
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# Prime the trie with a minimal query to force its construction
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prime = memoId "";
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in
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if control
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then builtins.seq prime key # Return key after priming
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else builtins.seq prime (memoId key) # Pass through memoization after priming
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