Squashed 'third_party/boostorg/odeint/' content from commit 6ff2719
Change-Id: If4892e29c1a5e6cf3a7aa51486a2725c251b0c7d
git-subtree-dir: third_party/boostorg/odeint
git-subtree-split: 6ff2719b6907b86596c3d43e88c1bcfdf29df560
diff --git a/performance/c_lorenz.c b/performance/c_lorenz.c
new file mode 100644
index 0000000..85aba7f
--- /dev/null
+++ b/performance/c_lorenz.c
@@ -0,0 +1,57 @@
+#include <stdio.h>
+#include <time.h>
+#include <math.h>
+
+void lorenz(const double *x, double *restrict y) {
+ y[0] = 10.0 * (x[1] - x[0]);
+ y[1] = 28.0 * x[0] - x[1] - x[0] * x[2];
+ y[2] = x[0] * x[1] - (8.0 / 3.0) * x[2];
+}
+
+int main(int argc, const char *argv[])
+{
+ const int nb_steps = 20000000;
+ const double h = 1.0e-10;
+ const double h2 = 0.5 * h;
+ const double nb_loops = 21;
+ double x[3];
+ double y[3];
+ double f1[3];
+ double f2[3];
+ double f3[3];
+ double f4[3];
+ double min_time = 1E6;
+ clock_t begin, end;
+ double time_spent;
+
+ for (int j = 0; j < nb_loops; j++) {
+ x[0] = 8.5;
+ x[1] = 3.1;
+ x[2] = 1.2;
+ begin = clock();
+ for (int k = 0; k < nb_steps; k++) {
+ lorenz(x, f1);
+ for (int i = 0; i < 3; i++) {
+ y[i] = x[i] + h2 * f1[i];
+ }
+ lorenz(y, f2);
+ for (int i = 0; i < 3; i++) {
+ y[i] = x[i] + h2 * f2[i];
+ }
+ lorenz(y, f3);
+ for (int i = 0; i < 3; i++) {
+ y[i] = x[i] + h * f3[i];
+ }
+ lorenz(y, f4);
+ for (int i = 0; i < 3; i++) {
+ x[i] = x[i] + h * (f1[i] + 2 * (f2[i] + f3[i]) + f4[i]) / 6.0;
+ }
+ }
+ end = clock();
+ min_time = fmin(min_time, (double)(end-begin)/CLOCKS_PER_SEC);
+ printf("Result: %f\t runtime: %f\n", x[0], (double)(end-begin)/CLOCKS_PER_SEC);
+ }
+ printf("Minimal Runtime: %f\n", min_time);
+
+ return 0;
+}