rmuir opened a new pull request, #12764: URL: https://github.com/apache/lucene/pull/12764
J9 VM doesn't seem to actually implement the vector api, so it falls back to hundreds-of-times-slower-pure-java impl. Currently: ``` VectorUtilBenchmark.floatCosineScalar 1024 thrpt 15 0.860 ± 0.011 ops/us VectorUtilBenchmark.floatCosineVector 1024 thrpt 75 0.010 ± 0.001 ops/us (!) VectorUtilBenchmark.floatDotProductScalar 1024 thrpt 15 2.325 ± 0.047 ops/us VectorUtilBenchmark.floatDotProductVector 1024 thrpt 75 0.021 ± 0.001 ops/us (!) VectorUtilBenchmark.floatSquareScalar 1024 thrpt 15 1.797 ± 0.020 ops/us VectorUtilBenchmark.floatSquareVector 1024 thrpt 75 0.015 ± 0.001 ops/us (!) ``` Look, i realize somehow it seems "culturally acceptable" in the java world to fall back to hundreds-of-times-slower code whenever it is convenient (e.g. `Math.fma` in the jdk), but this is so, so, so, wrong. We must never allow it to happen when it can be easily prevented: we have to detect and prevent such performance landmines. Many users have no idea of the differences between different JVMs and I don't want them hitting any traps like this. It may not really be their fault, perhaps some java-based software they are running is turning on the vector flags for them in a shell script/bat file, and they just happen to have J9 VM in their path. Patch: ``` Benchmark (size) Mode Cnt Score Error Units VectorUtilBenchmark.floatCosineScalar 1024 thrpt 15 0.858 ± 0.012 ops/us VectorUtilBenchmark.floatCosineVector 1024 thrpt 75 0.864 ± 0.002 ops/us VectorUtilBenchmark.floatDotProductScalar 1024 thrpt 15 2.327 ± 0.027 ops/us VectorUtilBenchmark.floatDotProductVector 1024 thrpt 75 2.331 ± 0.013 ops/us VectorUtilBenchmark.floatSquareScalar 1024 thrpt 15 1.782 ± 0.022 ops/us VectorUtilBenchmark.floatSquareVector 1024 thrpt 75 1.779 ± 0.021 ops/us ``` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org For additional commands, e-mail: issues-h...@lucene.apache.org
