[robert3005]

The list take by PiecewiseSequence compiled its gather kernels for every combination of piece start, piece length, list offset and output offset type (4 x 4 x 4 x 4). The kernels read each piece start and length only once per piece. The inner loop over list offsets depends only on the offset types. The take now widens the starts and lengths to u64 and dispatches only on the offset types.

The widening does not copy when the pieces are already u64, which is the type that the list take itself produces. For other widths it copies the piece arrays once. That copy is proportional to the number of pieces, not to the number of elements.

	before	after
vortex-array release __text (macOS arm64)	14,012,988 B	12,798,204 B (-1.21 MB)

[codspeed]

Merging this PR will degrade performance by 17.76%

4 warnings, 1 note

⚠️ Walltime results may be unreliable

Some benchmarks used the Walltime instrument outside CodSpeed Macro Runners, which can make the results inconsistent.

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⚠️ Unable to measure the execution of 2 benchmarks

These benchmarks measured no execution time, so their results are not comparable and count as unchanged. This usually happens when the compiler removes the code under test.

Prevent compiler optimizations

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⚠️ 16 benchmarks are dominated by system calls

System calls cannot be simulated consistently and are left out of the measure. The reported value understates the real cost. Switch to the Walltime instrument to measure them.

Learn more about system calls

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⚠️ Base and head ran on different runner types

Some benchmarks with significant performance changes were compared across different runner types, so the changes might not come from the code. Run base and head on the same runner type, or use CodSpeed Macro Runners for more stable results.

Learn more about Macro Runners

Open the report in CodSpeed to investigate

ℹ️ 40 benchmarks have no flamegraph

The flamegraph wasn't generated: the symbols of the profiling trace could not be resolved, because no information about the language frames was collected.

See affected benchmarks

⚡ 2 improved benchmarks
❌ 3 regressed benchmarks
✅ 2434 untouched benchmarks
⏩ 12 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	CPU Simulation	bench_compare_sliced_dict_primitive[(3333, 10000)]	32.9 µs	71.3 µs	-53.81%
❌	CPU Simulation	filter_powerlaw_by_random[250000]	131.3 µs	174.3 µs	-24.65%
❌	CPU Simulation	random_i8[0.01]	101.9 µs	115.5 µs	-11.84%
⚡	Walltime	threshold_avx512[80]	2.7 µs	2.5 µs	+10.81%
⚡	CPU Simulation	decompress[u16, (4000, 256)]	62.5 µs	56.5 µs	+10.66%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing rk/size-list-take-wide-pieces (699ffe0) with develop (76d8371)}

Footnotes

1. 12 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[robert3005]

This is really only a slow down if average list size is 1-4, otherwise it's noise