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run benchmark take_kernels |
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Dandandan
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run benchmark interleave_kernels |
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Hmm this looks actually worse on this machine (probably x86 vs ARM...)... |
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run benchmark take_kernels |
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run benchmark interleave_kernels |
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@comphead @andygrove FYI as you seem to be interested in sort performance (which is one of the consumers) |
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@mbutrovich as well :) |
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I'm curious what a SIMD gather (AVX2, SVE) intrinsics' performance is like vs. unrolling manually on modern architectures. The former likely ends up as similar μops anyway. I don't love specializing the code like this (in either direction, SIMD intrinsics or unrolling especially with ARM increasingly prevalent in the cloud) but if today it's faster I'm okay with it. It's also a pretty well-understood technique at this point. |
comphead
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Mar 12, 2026
| let chunks = indices.chunks_exact(8); | ||
| let remainder = chunks.remainder(); | ||
| for chunk in chunks { | ||
| let v0 = arrays[chunk[0].0].value(chunk[0].1); |
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thinking aloud, is 8 a constant? does it depend on number of cpu/threads, etc?
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It just a loop unrolling constant - the higher the more code it will generate inside the loop so it can hide more latency by running/pipelining the instructions not depending on the loads.
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yeah, thats what I was thinking if user may want to modify this value depending on their hardware/OS setup?
Or if someone would like to benchmark take or interleave with different chunks values, they would have to rewrite the method respectively? maybe some macro could help? it can be done as follow up if needed
comphead
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Mar 12, 2026
| .collect::<Vec<_>>(); | ||
| for idx in remainder { | ||
| // SAFETY: base < len == output capacity | ||
| unsafe { dst.add(base).write(arrays[idx.0].value(idx.1)) }; |
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for unsafe calls, would it make sense to debug_assert safety requirements to catch unexpected things on CI debug builds?
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Agreed. Auto-vectorization is preferred and in an ideal scenario we don't need to specialize the code and write our APIs so LLVM can generate good code automatically. Ideally I think, the I am thinking perhaps we can at least remove the bounds checks for |
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run benchmark interleave_kernels |
This reverts commit fc1adb9.
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Oh wait that is a not so useful idea as we get them for all of the rows (so it will be more expensive to check upfront than it is to do "on the go") |
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