RFR 8209171 : Simplify Java implementation of Integer/Long.numberOfTrailingZeros() (original) (raw)

Ivan Gerasimov ivan.gerasimov at oracle.com
Thu Aug 9 23:45:07 UTC 2018

Hi Joe!

On 8/9/18 4:20 PM, Joseph D. Darcy wrote:

Hi Ivan,

On which platforms were the benchmark numbers collected? Ah, yes, should have mentioned that. macOS 10.13.5 High Sierra, processor 3.1 GHz Intel Core i7

With kind regards, Ivan

Thanks, > -Joe > On 8/9/2018 4:15 PM, Ivan Gerasimov wrote: > Hello! >>> Integer.numberOfTrailingZeros() and Long.numberOfTrailingZeros() are > intrinsified by Hotspot, so the Java implementation of these is not > too important. > However, they still can be improved by a tiny bit :) >>> Could you please help review the fix? >>> Bug: https://bugs.openjdk.java.net/browse/JDK-8209171 > Webrev: http://cr.openjdk.java.net/~igerasim/8209171/00/webrev/ > Benchmark for Integer: > http://cr.openjdk.java.net/~igerasim/8209171/00/bench/int/MyBenchmark.java > Benchmark for Long: > http://cr.openjdk.java.net/~igerasim/8209171/00/bench/long/MyBenchmark.java >>> The resulting code is both smaller and faster. It may also help to > warm up Integer.numberOfLeadingZeros() quicker. >>> On average, the new Integer.numberOfTrailingZeros() has got +11% to > performance for -client and +1% for -server. > Long.numberOfTrailingZeros() is faster on 17% for -client and +20% > for -server. >>>

With kind regards, Ivan Gerasimov

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