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83 lines
2.6 KiB
C
83 lines
2.6 KiB
C
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/*
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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* Neither the name of "The Computer Language Benchmarks Game" nor the
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name of "The Computer Language Shootout Benchmarks" nor the names of
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its contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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/* -*- mode: c -*-
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*
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* The Great Computer Language Shootout
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* http://shootout.alioth.debian.org/
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*
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* Contributed by Sebastien Loisel
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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double eval_A(int i, int j) { return 1.0/((i+j)*(i+j+1)/2+i+1); }
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void eval_A_times_u(int N, const double u[], double Au[])
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{
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int i,j;
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for(i=0;i<N;i++)
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{
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Au[i]=0;
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for(j=0;j<N;j++) Au[i]+=eval_A(i,j)*u[j];
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}
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}
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void eval_At_times_u(int N, const double u[], double Au[])
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{
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int i,j;
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for(i=0;i<N;i++)
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{
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Au[i]=0;
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for(j=0;j<N;j++) Au[i]+=eval_A(j,i)*u[j];
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}
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}
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void eval_AtA_times_u(int N, const double u[], double AtAu[])
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{ double v[N]; eval_A_times_u(N,u,v); eval_At_times_u(N,v,AtAu); }
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int main(int argc, char *argv[])
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{
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int i;
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int N = ((argc == 2) ? atoi(argv[1]) : 2000);
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double u[N],v[N],vBv,vv;
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for(i=0;i<N;i++) u[i]=1;
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for(i=0;i<10;i++)
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{
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eval_AtA_times_u(N,u,v);
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eval_AtA_times_u(N,v,u);
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}
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vBv=vv=0;
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for(i=0;i<N;i++) { vBv+=u[i]*v[i]; vv+=v[i]*v[i]; }
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printf("%0.9f\n",sqrt(vBv/vv));
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return 0;
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}
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