115 lines
2.3 KiB
C++
115 lines
2.3 KiB
C++
#include <cassert>
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#include <chrono> // timing
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#include <cmath> // sqrt()
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#include <cstdlib> // atoi()
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#include <cstring> // strncmp()
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#include <ctime>
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#include <iostream>
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#include <sstream>
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#include <vector>
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#include <lapacke.h>
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#include "timing.h"
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#include "benchmark.h"
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using namespace std;
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using namespace std::chrono; // timing
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int main()
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{
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unsigned int n= 32;
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vector<double> M(n*n,4.0);
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for(unsigned int i=0; i<n; i++)
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{
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for(unsigned int j=0; j<n; j++)
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{
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if(i!=j)
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{
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double diff = i-j;
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M[i*n+j] = 1.0/(diff*diff);
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}
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}
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}
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vector<double> M2 = M;
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vector<int> ipiv(n); //pivots
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LAPACKE_dgetrf(LAPACK_ROW_MAJOR,n,n, M.data(),n,ipiv.data()); //M=PLU
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double time;
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unsigned int nhrsmax = 1000000;
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for(unsigned int i=nhrsmax/10; i < nhrsmax;i+=nhrsmax/10)
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{
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unsigned int nhrs = i;
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//FOR CHECKING
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vector<double> X(n*nhrs,1.0);
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vector<double> b = benchmark_C(M2,X,n);
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tic();
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LAPACKE_dgetrs(LAPACK_ROW_MAJOR,'N',n,nhrs,M.data(),n,ipiv.data(),b.data(),nhrs);
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time = toc();
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cout << "Time for nhrs=" << nhrs << ": " << time << endl;
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double max_err = 0.0;
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for (unsigned int j = 0; j < n * nhrs; j++)
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{
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double err = b[j] - X[j];
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err *= err;
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if (err > max_err) max_err = err;
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}
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cout <<"max err^2:" << max_err <<endl;
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cout <<endl;
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}
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/*
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Time for nhrs=100000: 0.0605495
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max err^2:4.93038e-32
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Time for nhrs=200000: 0.127608
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max err^2:4.93038e-32
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Time for nhrs=300000: 0.182197
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max err^2:4.93038e-32
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Time for nhrs=400000: 0.202608
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max err^2:4.93038e-32
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Time for nhrs=500000: 0.24484
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max err^2:4.93038e-32
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Time for nhrs=600000: 0.298055
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max err^2:4.93038e-32
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Time for nhrs=700000: 0.362414
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max err^2:4.93038e-32
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Time for nhrs=800000: 0.410004
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max err^2:4.93038e-32
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Time for nhrs=900000: 0.492339
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max err^2:4.93038e-32
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Time grows slow (linearly)
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*/
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return 0;
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}
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