58 lines
1.5 KiB
C
58 lines
1.5 KiB
C
#include <stdio.h>
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#include <time.h>
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#include <math.h>
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void lorenz(const double *x, double *restrict y) {
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y[0] = 10.0 * (x[1] - x[0]);
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y[1] = 28.0 * x[0] - x[1] - x[0] * x[2];
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y[2] = x[0] * x[1] - (8.0 / 3.0) * x[2];
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}
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int main(int argc, const char *argv[])
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{
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const int nb_steps = 20000000;
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const double h = 1.0e-10;
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const double h2 = 0.5 * h;
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const double nb_loops = 21;
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double x[3];
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double y[3];
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double f1[3];
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double f2[3];
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double f3[3];
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double f4[3];
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double min_time = 1E6;
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clock_t begin, end;
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double time_spent;
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for (int j = 0; j < nb_loops; j++) {
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x[0] = 8.5;
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x[1] = 3.1;
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x[2] = 1.2;
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begin = clock();
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for (int k = 0; k < nb_steps; k++) {
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lorenz(x, f1);
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for (int i = 0; i < 3; i++) {
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y[i] = x[i] + h2 * f1[i];
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}
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lorenz(y, f2);
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for (int i = 0; i < 3; i++) {
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y[i] = x[i] + h2 * f2[i];
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}
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lorenz(y, f3);
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for (int i = 0; i < 3; i++) {
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y[i] = x[i] + h * f3[i];
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}
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lorenz(y, f4);
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for (int i = 0; i < 3; i++) {
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x[i] = x[i] + h * (f1[i] + 2 * (f2[i] + f3[i]) + f4[i]) / 6.0;
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}
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}
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end = clock();
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min_time = fmin(min_time, (double)(end-begin)/CLOCKS_PER_SEC);
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printf("Result: %f\t runtime: %f\n", x[0], (double)(end-begin)/CLOCKS_PER_SEC);
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}
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printf("Minimal Runtime: %f\n", min_time);
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return 0;
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}
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