Initial

uebung_02/main_matrix.c

@@ -0,0 +1,64 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int compute(int N) {
+
+  int i_0, i_1;
+  // claim space
+  double **A = (double **)malloc(sizeof(double *) * N);
+  for (i_0 = 0; i_0 < N; i_0++) {
+    A[i_0] = (double *)malloc(sizeof(double) * N);
+  }
+  double *x = (double *)malloc(sizeof(double) * N);
+  double *y = (double *)malloc(sizeof(double) * N);
+  double *y_sol = (double *)malloc(sizeof(double) * N);
+
+  // fill matrix and vector
+  for (i_0 = 0; i_0 < N; i_0++) {
+    x[i_0] = i_0 + 1;
+    y_sol[i_0] = (i_0 + 1) * N;
+    for (i_1 = 0; i_1 < N; i_1++) {
+      A[i_0][i_1] = (i_0 + 1.0) / (i_1 + 1.0);
+    }
+  }
+
+  // for (i_0 = 0; i_0 < N; i_0++){
+  // 	printf("[ ");
+  // 	for(i_1 = 0; i_1 < N; i_1++){
+  // 		printf("%.3f ",A[i_0][i_1]);
+  // 	}
+  // 	printf("]");
+  // 	printf("[ %.1f ] = [ %.1f ][ %.1f ]\n",x[i_0],y[i_0],y_sol[i_0]);
+  // }
+
+  // compute matrix-vector product
+  for (i_0 = 0; i_0 < N; i_0++) {
+    y[i_0] = 0;
+    for (i_1 = 0; i_1 < N; i_1++) {
+      y[i_0] += A[i_0][i_1] * x[i_1];
+    }
+  }
+
+  // compare result to solution
+  double sum = 0.0;
+  for (i_0 = 0; i_0 < N; i_0++) {
+    sum += (y[i_0] - y_sol[i_0]) * (y[i_0] - y_sol[i_0]);
+  }
+
+  return sum;
+}
+
+int main(int argc, char *argv[]) {
+
+  int N;
+  if (argc != 2) {
+    N = 1000;
+  } else {
+    N = atoi(argv[1]); // Convert the argument to an integer
+  }
+
+  double err = compute(N);
+  printf("Error for N = %d: %.8f\n", N, err);
+
+  return 0;
+}

uebung_02/main_openmp.c

@@ -0,0 +1,19 @@
+#include <omp.h> // load Open-MP library
+#include <stdio.h>
+#include <stdlib.h>
+
+int main() {
+  int N = 5;
+  int num;
+
+#pragma omp parallel for private(num) // start Open-MP section
+  // here the program (1 thread) is split into multiple threads
+  // each thread has its own copy of i (loop) and num (private)
+  // all threads share N (by default, because defined outside)
+  for (int i = 0; i < N; i++) {
+    num = omp_get_thread_num();
+    printf("Thread %d does iteration %d\n", num, i);
+  }
+
+  return 0;
+}