8 ms·

No, GenericWriter takes a function at compile time and it gives you a GenericWriter struct that calls that function (at compile time), no function pointers need

by nmilo 2y ago

No, GenericWriter takes a function at compile time and it gives you a GenericWriter struct that calls that function (at compile time), no function pointers needed.

deleted 2y ago
[deleted]
latch 2y ago
There's definitely overhead with the GenericWriter, seeing as it uses the AnyWriter for every call except `write` (1) genericWriter - 31987.66ns per iterations appendSlice - 20112.35ns per iterations appendSliceOptimized - 12996.49ns per iterations `appendSliceOptimized` is implemented using knowledge of the underlying writer, the way that say an interface implementation in Go would be able to. It's a big part of the reason that reading a file in Zig line-by-line can be so much slower than in other languages (2) (1) https://gist.github.com/karlseguin/1d189f683797b0ee00cdb8186f23af98 https://gist.github.com/karlseguin/1d189f683797b0ee00cdb8186... (2) https://github.com/ziglang/zig/issues/17985 https://github.com/ziglang/zig/issues/17985
- josephg 2y ago
  Nice! It'd be fun to see a comparison in rust if anyone is keen. - Both code and resulting performance.
  - josephg 2y ago
    I was curious, so I ran your zig version myself and ported it to rust[1]. I think you forgot to run your benchmark in release mode. In debug mode, I get similar results to you. But in release mode, it runs ~5x faster than you reported: genericWriter - 4035.47ns per iterations appendSlice - 4026.41ns per iterations appendSliceOptimized - 2884.84ns per iterations I bet the first two implementations are emitting identical code. But appendSliceOptimized is clearly much more efficient. For some reason, rust is about twice as fast as zig in this test: generic_writer time: [1.8812 µs 1.8837 µs 1.8870 µs] append_slice time: [2.0019 µs 2.0065 µs 2.0126 µs] append_slice_raw time: [1.6932 µs 1.7041 µs 1.7182 µs] (1µs = 1000ns) [1] https://gist.github.com/josephg/e2dd6e7baf0a764a21bd724f8a2e411b https://gist.github.com/josephg/e2dd6e7baf0a764a21bd724f8a2e... Tests running on linux 6.8.0, CPU: Ryzen 7950x. zig v0.13 / rust v1.84.1. Zig command: zig build --release=fast -Dtarget=native run Rust command: RUSTFLAGS='-C target-cpu=native' cargo run --release -- --bench

by nmilo 2y ago

No, GenericWriter takes a function at compile time and it gives you a GenericWriter struct that calls that function (at compile time), no function pointers needed.

deleted 2y ago

[deleted]

latch 2y ago

There's definitely overhead with the GenericWriter, seeing as it uses the AnyWriter for every call except `write` (1) genericWriter - 31987.66ns per iterations appendSlice - 20112.35ns per iterations appendSliceOptimized - 12996.49ns per iterations `appendSliceOptimized` is implemented using knowledge of the underlying writer, the way that say an interface implementation in Go would be able to. It's a big part of the reason that reading a file in Zig line-by-line can be so much slower than in other languages (2) (1) https://gist.github.com/karlseguin/1d189f683797b0ee00cdb8186f23af98 https://gist.github.com/karlseguin/1d189f683797b0ee00cdb8186... (2) https://github.com/ziglang/zig/issues/17985 https://github.com/ziglang/zig/issues/17985

josephg 2y ago
Nice! It'd be fun to see a comparison in rust if anyone is keen. - Both code and resulting performance.
- josephg 2y ago
  I was curious, so I ran your zig version myself and ported it to rust[1]. I think you forgot to run your benchmark in release mode. In debug mode, I get similar results to you. But in release mode, it runs ~5x faster than you reported: genericWriter - 4035.47ns per iterations appendSlice - 4026.41ns per iterations appendSliceOptimized - 2884.84ns per iterations I bet the first two implementations are emitting identical code. But appendSliceOptimized is clearly much more efficient. For some reason, rust is about twice as fast as zig in this test: generic_writer time: [1.8812 µs 1.8837 µs 1.8870 µs] append_slice time: [2.0019 µs 2.0065 µs 2.0126 µs] append_slice_raw time: [1.6932 µs 1.7041 µs 1.7182 µs] (1µs = 1000ns) [1] https://gist.github.com/josephg/e2dd6e7baf0a764a21bd724f8a2e411b https://gist.github.com/josephg/e2dd6e7baf0a764a21bd724f8a2e... Tests running on linux 6.8.0, CPU: Ryzen 7950x. zig v0.13 / rust v1.84.1. Zig command: zig build --release=fast -Dtarget=native run Rust command: RUSTFLAGS='-C target-cpu=native' cargo run --release -- --bench