On Fri, 29 Jul 2022 03:55:54 GMT, Xiaohong Gong <xg...@openjdk.org> wrote:
> Vector API binary op "`FIRST_NONZERO`" represents the vector operation of "`a > != 0 ? a : b`", which can be implemented with existing APIs like "`compare + > blend`". The current implementation is more complex especially for the > floating point type vectors. The main idea is: > > > 1) mask = a.compare(0, ne); > 2) b = b.blend(0, mask); > 3) result = a | b; > > > And for the floating point types, it needs the vector reinterpretation > between the floating point type and the relative integral type, since the > final "`OR`" operation is only valid for bitwise integral types. > > A simpler implementation is: > > > 1) mask = a.compare(0, eq); > 2) result = a.blend(b, mask); > > > This could save the final "`OR`" operation and the related reinterpretation > between FP and integral types. > > Here are the performance data of the "`FIRST_NONZERO`" benchmarks (please see > the benchmark details for byte vector from [1]) on ARM NEON system: > > Benchmark (size) Mode Cnt Before After Units > ByteMaxVector.FIRST_NONZERO 1024 thrpt 15 12107.422 18385.157 ops/ms > ByteMaxVector.FIRST_NONZEROMasked 1024 thrpt 15 9765.282 14739.775 ops/ms > DoubleMaxVector.FIRST_NONZERO 1024 thrpt 15 1798.545 2331.214 ops/ms > DoubleMaxVector.FIRST_NONZEROMasked 1024 thrpt 15 1211.838 1810.644 ops/ms > FloatMaxVector.FIRST_NONZERO 1024 thrpt 15 3491.924 4377.167 ops/ms > FloatMaxVector.FIRST_NONZEROMasked 1024 thrpt 15 2307.085 3606.576 ops/ms > IntMaxVector.FIRST_NONZERO 1024 thrpt 15 3602.727 5610.258 ops/ms > IntMaxVector.FIRST_NONZEROMasked 1024 thrpt 15 2726.843 4210.741 ops/ms > LongMaxVector.FIRST_NONZERO 1024 thrpt 15 1819.886 2974.655 ops/ms > LongMaxVector.FIRST_NONZEROMasked 1024 thrpt 15 1337.737 2315.094 ops/ms > ShortMaxVector.FIRST_NONZERO 1024 thrpt 15 6603.642 9586.320 ops/ms > ShortMaxVector.FIRST_NONZEROMasked 1024 thrpt 15 5222.006 7991.443 ops/ms > > We can also observe the similar improvement on x86 system. > > [1] > https://github.com/openjdk/panama-vector/blob/vectorIntrinsics/test/micro/org/openjdk/bench/jdk/incubator/vector/operation/ByteMaxVector.java#L266 LGTM. ------------- Marked as reviewed by eliu (Author). PR: https://git.openjdk.org/jdk/pull/9683
