111 lines
No EOL
2.4 KiB
C++
111 lines
No EOL
2.4 KiB
C++
#include <benchmark/benchmark.h>
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#include <random>
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#include <cmath>
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#include <iostream>
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/*
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Cephes Math Library Release 2.2: June, 1992
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Copyright 1984, 1987, 1989 by Stephen L. Moshier
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Direct inquiries to 30 Frost Street, Cambridge, MA 02140
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*/
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/* Single precision exponential function.
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* test interval: [-0.5, +0.5]
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* trials: 80000
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* peak relative error: 7.6e-8
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* rms relative error: 2.8e-8
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*/
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static float MAXNUMF = 3.4028234663852885981170418348451692544e38;
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static float MAXLOGF = 88.72283905206835;
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static float MINLOGF = -103.278929903431851103; /* log(2^-149) */
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static float LOG2EF = 1.44269504088896341;
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static float C1 = 0.693359375;
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static float C2 = -2.12194440e-4;
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float cephes_expf(float xx) {
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float x, z;
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int n;
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x = xx;
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if( x > MAXLOGF)
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{
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//mtherr( "expf", OVERFLOW );
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return( MAXNUMF );
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}
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if( x < MINLOGF )
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{
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//mtherr( "expf", UNDERFLOW );
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return(0.0);
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}
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/* Express e**x = e**g 2**n
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* = e**g e**( n loge(2) )
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* = e**( g + n loge(2) )
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*/
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z = floorf( LOG2EF * x + 0.5 ); /* floor() truncates toward -infinity. */
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x -= z * C1;
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x -= z * C2;
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n = z;
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z = x * x;
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/* Theoretical peak relative error in [-0.5, +0.5] is 4.2e-9. */
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z =
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((((( 1.9875691500E-4f * x
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+ 1.3981999507E-3f) * x
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+ 8.3334519073E-3f) * x
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+ 4.1665795894E-2f) * x
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+ 1.6666665459E-1f) * x
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+ 5.0000001201E-1f) * z
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+ x
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+ 1.0;
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/* multiply by power of 2 */
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x = ldexpf( z, n );
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return( x );
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}
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static void Dummy(benchmark::State& state) {
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std::random_device rd { };
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std::mt19937 gen { rd() };
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std::normal_distribution<float> dist { };
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for (auto _ : state)
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{
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auto value = dist(gen);
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benchmark::DoNotOptimize(value);
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}
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}
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static void StdExp(benchmark::State& state) {
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std::random_device rd { };
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std::mt19937 gen { rd() };
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std::normal_distribution<float> dist { };
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for (auto _ : state)
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{
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auto value = std::exp(dist(gen));
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benchmark::DoNotOptimize(value);
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}
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}
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static void CephesExp(benchmark::State& state) {
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std::random_device rd { };
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std::mt19937 gen { rd() };
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std::normal_distribution<float> dist { };
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for (auto _ : state)
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{
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auto value = cephes_expf(dist(gen));
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benchmark::DoNotOptimize(value);
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}
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}
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BENCHMARK(Dummy);
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BENCHMARK(StdExp);
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BENCHMARK(CephesExp);
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BENCHMARK_MAIN(); |