4.x: Improve Buffer via dedicated exact/skip implementations #665
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quinmars
reviewed
Jun 27, 2018
| { | ||
| var idx = _index; | ||
| var buffer = _buffer; | ||
| if (idx == 0) |
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I'd prefer if you test here for buffer == null. I know it's the same, but when I read it the first time without knowing the end I was a little bit alarmed.
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That would be logically incorrect because once the short buffer ends after count, there is a window between count + 1 .. skip where buffer is null and no new buffer should be created.
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Wait, the conversation page shows your comment for line 46 but the changes page shows this for line 125:
quinmars
approved these changes
Jun 27, 2018
danielcweber
approved these changes
Jun 28, 2018
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This PR improves the counted
Bufferoperator by having dedicated exact (count == skip) and gapped (count < skip) implementations because these cases require only one buffer to be handled instead of the overhead of a queue holding at most one buffer.The PR also adds a benchmark to verify the gains:
Improvement of Exact: 9.1%
Improvement of Skip: 6.1%
The Overlap (aka original algorithm) is practically the same within the noise range.
I've tried with a non-modulo algorithm for Overlap but it consistently produced 10 us slower results. I'm not sure why; I assume the special small numbers in the benchmark (1, 2) were JIT'd into binary-and and thus was much faster than an increment-test-store approach like the other two.