Update

openmp/8-dotproduct-v0-time.cpp

+#include <stdio.h>
+#include <stdlib.h>
+#include <omp.h>
+#define MAX_THREADS 128
+
+double T = 0.0;
+float dotproduct(float *x, float *y, int n)
+{
+  int i;
+  int nthreads = 0;
+  float d[MAX_THREADS];
+  float r;
+  double t0 = omp_get_wtime();
+  #pragma omp parallel shared(x,y,d, nthreads), private(i), firstprivate(n)
+  {
+    #pragma omp master
+    nthreads = omp_get_num_threads();
+    
+    int tid = omp_get_thread_num();
+    d[tid]=0;
+    #pragma omp for schedule(static)
+    for (i=0; i<n; i++) {
+      d[tid] += x[i]*y[i];
+    }
+  }
+  for (i=0; i<nthreads; ++i)
+    r+=d[i];
+  double t1 = omp_get_wtime();
+  printf("Time: %f\n", t1-t0);
+  T += t1-t0;
+  return r;
+}
+
+int main(int argc, char** argv)
+{
+  int N = atoi(argv[1]);
+  float* x = new float[N];
+  float* y = new float[N];
+
+  #pragma omp parallel for schedule(static)
+  for (int i=0; i<N; i++) {
+    x[i] = 1.0/double(i);
+    y[i] = N/double(i);
+  }
+
+  for (int i=0; i<10; ++i)
+  {
+    float d = dotproduct(x,y,N);
+  }
+  printf("Avrg: %f\n", T/10);
+  return 0;
+}
+