On Wed, 27 Nov 2024 11:21:32 GMT, Maurizio Cimadamore <mcimadam...@openjdk.org> wrote:
>> This PR proposes adding a _JDK-internal_ method for calculating hash codes >> for content in a `MemorySegment`. >> >> The internal method uses a polynomial 32-bit hash function equivalent to >> `Arrays::hashCode`. The new method is almost two times faster than naïvely >> iterating over individual bytes for larger regions. Also, it is more lean on >> inlining space compared to a naïve loop. >> >> >> >> Benchmark (ELEM_SIZE) Mode Cnt Score Error >> Units >> SegmentBulkHash.array 8 avgt 30 2.645 ? 0.078 >> ns/op >> SegmentBulkHash.array 64 avgt 30 6.062 ? 0.171 >> ns/op >> SegmentBulkHash.heapSegment 8 avgt 30 4.181 ? 0.145 >> ns/op >> SegmentBulkHash.heapSegment 64 avgt 30 25.716 ? 1.043 >> ns/op >> SegmentBulkHash.nativeSegment 8 avgt 30 3.939 ? 0.150 >> ns/op >> SegmentBulkHash.nativeSegment 64 avgt 30 23.262 ? 0.694 >> ns/op >> SegmentBulkHash.nativeSegmentJava 8 avgt 30 5.219 ? 0.183 >> ns/op <- Naïve iteration >> SegmentBulkHash.nativeSegmentJava 64 avgt 30 39.668 ? 1.040 >> ns/op <- Naïve iteration >> >> >>  >> >> >> If internal JDK code uses this method, it will automatically benefit from >> future performance improvements that can be implemented once the Vector API >> becomes available. > > test/jdk/java/foreign/TestSegmentBulkOperationsContentHash.java line 49: > >> 47: import static org.junit.jupiter.api.Assertions.*; >> 48: >> 49: final class TestSegmentBulkOperationsContentHash { > > Should we add a test which checks that the result of the content hash is the > same as the polynomial described in the javadoc? We test it is the same as `Arrays.hashCode(byte[])` which implements this scheme. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/22364#discussion_r1860660343
