34 lines
No EOL
872 B
C++
34 lines
No EOL
872 B
C++
#include "mylib.h"
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#include <cassert> // assert()
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#include <cmath>
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#include <vector>
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using namespace std;
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double scalar(vector<double> const &x, vector<double> const &y)
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{
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assert(x.size() == y.size());
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size_t const N = x.size();
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double sum = 0.0;
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for (size_t i = 0; i < N; ++i)
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{
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sum += x[i] * y[i];
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}
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return sum;
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}
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double Kahan_skalar(vector<double> const &x, vector<double> const &y)
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{
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double sum = 0;
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double c = 0;
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size_t n = x.size();
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for (size_t i = 0; i < n; ++i)
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{
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double z = x[i]*y[i] - c; // c is the part that got lost in the last iteration
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double t = sum + z; // when adding sum + z, the lower digits are lost if sum is large
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c = (t - sum) - z; // now we recover the lower digits to add in the next iteration
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sum = t;
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}
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return sum;
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} |