Antoine Pitrou created ARROW-10058:
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Summary: [C++] Investigate performance of LevelsToBitmap without
BMI2
Key: ARROW-10058
URL: https://issues.apache.org/jira/browse/ARROW-10058
Project: Apache Arrow
Issue Type: Sub-task
Components: C++
Reporter: Antoine Pitrou
Currently, when some Parquet nested data involves some repetition levels,
converting the levels to bitmap goes through a slow scalar path unless the BMI2
instruction set is available and efficient (the latter using the PEXT
instruction to process 16 levels at once).
It may be possible to emulate PEXT for 5- or 6-bit masks by using a lookup
table, allowing to process 5-6 levels at once.
(also, it would be good to add nested reading benchmarks for non-trivial
nesting; currently we only benchmark one-level struct and one-level list)
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