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mirror of https://github.com/golang/go synced 2024-11-12 03:40:21 -07:00

parallel spectral-norm

R=rsc
DELTA=85  (84 added, 1 deleted, 0 changed)
OCL=32810
CL=32810
This commit is contained in:
Rob Pike 2009-08-05 18:44:49 -07:00
parent 8764ebee95
commit 158f3f6440
2 changed files with 112 additions and 1 deletions

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@ -0,0 +1,111 @@
/*
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of "The Computer Language Benchmarks Game" nor the
name of "The Computer Language Shootout Benchmarks" nor the names of
its contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/
/* The Computer Language Benchmarks Game
* http://shootout.alioth.debian.org/
*
* contributed by The Go Authors.
* Based on spectral-norm.c by Sebastien Loisel
*/
package main
import (
"flag";
"fmt";
"math";
)
var n = flag.Int("n", 2000, "count")
var nCPU = flag.Int("ncpu", 4, "number of cpus")
func evalA(i, j int) float64 {
return 1 / float64(((i + j)*(i + j + 1)>>1+ i + 1));
}
type Vec []float64
func (v Vec) Times(i, n int, u Vec, c chan int) {
for ; i < n; i++ {
v[i] = 0;
for j := 0; j < len(u); j++ {
v[i] += evalA(i, j)*u[j];
}
}
c <- 1;
}
func (v Vec) TimesTransp(i, n int, u Vec, c chan int) {
for ; i < n; i++ {
v[i] = 0;
for j := 0; j < len(u); j++ {
v[i] += evalA(j, i)*u[j];
}
}
c <- 1;
}
func wait(c chan int) {
for i := 0; i < *nCPU; i++ {
<-c
}
}
func (v Vec) ATimesTransp(u Vec) {
x := make(Vec, len(u));
c := make(chan int, *nCPU);
for i := 0; i < *nCPU; i++ {
go x.Times(i*len(v) / *nCPU, (i+1)*len(v) / *nCPU, u, c);
}
wait(c);
for i := 0; i < *nCPU; i++ {
go v.TimesTransp(i*len(v) / *nCPU, (i+1)*len(v) / *nCPU, x, c);
}
wait(c);
}
func main() {
flag.Parse();
N := *n;
u := make(Vec, N);
for i := 0; i < N; i++ {
u[i] = 1;
}
v := make(Vec, N);
for i := 0; i < 10; i++ {
v.ATimesTransp(u);
u.ATimesTransp(v);
}
var vBv, vv float64;
for i := 0; i < N; i++ {
vBv += u[i]*v[i];
vv += v[i]*v[i];
}
fmt.Printf("%0.9f\n", math.Sqrt(vBv/vv));
}

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@ -64,5 +64,5 @@ spectral-norm 5500
gccgo -O2 spectral-norm.go 12.20u 0.00s 12.23r
gc spectral-norm 50.23u 0.00s 50.36r
gc_B spectral-norm 49.69u 0.01s 49.83r
gc spectral-norm-parallel 24.47u 0.03s 11.05r # has shift >>1 not div /2
[using >>1 instead of /2 : gc gives 24.33u 0.00s 24.33r]