Hi, Here are very basic benchmark results from (JaFaMa 2 - FastMathPerf) made on my laptop (i7-6820HQ set @ 2Ghz + JDK8): --- testing asin(double) --- Loop on Math.asin(double) took 6.675 s Loop on FastMath.asin(double) took 0.162 s
--- testing acos(double) --- Loop on Math.acos(double) took 6.332 s Loop on FastMath.acos(double) took 0.16 s --- testing atan(double) --- Loop on Math.atan(double) took 0.766 s Loop on FastMath.atan(double) took 0.167 --- testing sqrt(double) --- Loop on Math.sqrt(double), args in [0.0,10.0], took 0.095 s Loop on FastMath.sqrt(double), args in [0.0,10.0], took 0.097 s Loop on Math.sqrt(double), args in [0.0,1.0E12], took 0.109 s Loop on FastMath.sqrt(double), args in [0.0,1.0E12], took 0.093 s Loop on Math.sqrt(double), args in all magnitudes (>=0), took 0.091 s Loop on FastMath.sqrt(double), args in all magnitudes (>=0), took 0.092 --- testing cbrt(double) --- Loop on Math.cbrt(double), args in [-10.0,10.0], took 1.152 s Loop on FastMath.cbrt(double), args in [-10.0,10.0], took 0.195 s Loop on Math.cbrt(double), args in [-1.0E12,1.0E12], took 1.153 s Loop on FastMath.cbrt(double), args in [-1.0E12,1.0E12], took 0.193 s Loop on Math.cbrt(double), args in all magnitudes, took 1.154 s Loop on FastMath.cbrt(double), args in all magnitudes, took 0.272 --- testing cbrt(double) = pow(double, 1/3) --- Loop on Math.pow(double, 1/3), args in [-10.0,10.0], took 0.739 s Loop on FastMath.cbrt(double), args in [-10.0,10.0], took 0.166 s Loop on Math.pow(double, 1/3), args in [-0.7,0.7], took 0.746 s Loop on FastMath.cbrt(double), args in [-0.7,0.7], took 0.166 s Loop on Math.pow(double, 1/3), args in [-0.1,0.1], took 0.742 s Loop on FastMath.cbrt(double), args in [-0.1,0.1], took 0.165 s Loop on Math.pow(double, 1/3), args in all magnitudes, took 0.753 s Loop on FastMath.cbrt(double), args in all magnitudes, took 0.244 Conclusion: - acos / asin / atan functions are quite slow: it confirms these are not optimized by hotspot intrinsics. - cbrt() is slower than sqrt() : 1.1s vs 0.1 => 10x slower - cbrt() is slower than pow(1/3) : 1.1s vs 0.7s => 50% slower Any plan to enhance these specific math operations ? Laurent 2017-11-09 14:33 GMT+01:00 Laurent Bourgès <bourges.laur...@gmail.com>: > I checked in the latest jdk master and both cbrt / acos are NOT intrinsics. > > However, cbrt(x) = pow(x, 1/3) so it may be optmized... > > Could someone tell me how cbrt() is concretely implemented ? > > In native libfdm, there is no e_cbrt.c ! > > Thanks for your help, > Laurent > > Le 9 nov. 2017 10:52 AM, "Jonas Konrad" <m...@yawk.at> a écrit : > >> Hey, >> >> Most functions in the Math class are intrinsic ( >> http://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/file/tip/src/ >> share/vm/classfile/vmSymbols.hpp#l664 ) and will use native instructions >> where available. You can also test this yourself using jitwatch. There is >> no native call overhead. >> >> The standard library does not currently include less accurate but faster >> Math functions, maybe someone else can answer if that is something to be >> considered. >> >> - Jonas Konrad >> >> On 11/09/2017 10:00 AM, Laurent Bourgès wrote: >> >>> Hi, >>> >>> The Marlin renderer (JEP265) uses few Math functions: sqrt, cbrt, acos... >>> >>> Could you check if the current JDK uses C2 intrinsics or libfdm (native / >>> JNI overhead?) and tell me if such functions are already highly optimized >>> in jdk9 or 10 ? >>> >>> Some people have implemented their own fast Math like Apache Commons Math >>> or JaFaMa libraries that are 10x faster for acos / cbrt. >>> >>> I wonder if I should implement my own cbrt function (cubics) in pure java >>> as I do not need the highest accuracy but SPEED. >>> >>> Would it sound possible to have a JDK FastMath public API (lots faster >>> but >>> less accurate?) >>> >>> Do you know if recent CPU (intel?) have dedicated instructions for such >>> math operations ? >>> Why not use it instead? >>> Maybe that's part of the new Vectorization API (panama) ? >>> >>> Cheers, >>> Laurent Bourges >>> >>> -- -- Laurent Bourgès
