1 /*
2 A simplification of the Stream benchmark for OpenMP
3 Original code developed by John D. McCalpin
4 */
5 #include <stdio.h>
6 #include <math.h>
7 #include <limits.h>
8 #include <float.h>
9 #include <sys/time.h>
10 #include <stdlib.h>
11 #include <petscsys.h>
12
13 //#define N 2*4*20000000
14 #define N 80000000
15 //#define N 1200000
16 //#define N 120000
17 #define NTIMES 50
18 #define OFFSET 0
19
20 #if !defined(MIN)
21 #define MIN(x, y) ((x) < (y) ? (x) : (y))
22 #endif
23 #if !defined(MAX)
24 #define MAX(x, y) ((x) > (y) ? (x) : (y))
25 #endif
26
27 static double a[N + OFFSET], b[N + OFFSET], c[N + OFFSET];
28 static double mintime = FLT_MAX;
29 static double bytes = 3 * sizeof(double) * N;
30
main(int argc,char ** argv)31 int main(int argc, char **argv)
32 {
33 MPI_Init(&argc, &argv);
34 const static double scalar = 3.0;
35 #pragma omp threadprivate(scalar)
36 double times[NTIMES], rate;
37 int size;
38 char *env;
39 FILE *fd;
40
41 env = getenv("OMP_NUM_THREADS");
42 if (!env) env = (char *)"1";
43 sscanf(env, "%d", &size);
44
45 #pragma omp parallel for schedule(static)
46 for (int j = 0; j < N; j++) {
47 a[j] = 1.0;
48 b[j] = 2.0;
49 c[j] = 3.0;
50 }
51
52 /* --- MAIN LOOP --- repeat test cases NTIMES times --- */
53 for (int k = 0; k < NTIMES; k++) {
54 times[k] = MPI_Wtime();
55 // https://www.openmp.org/wp-content/uploads/OpenMP-API-Specification-5-2.pdf
56 // #pragma omp parallel for (same performance as below)
57 // #pragma omp parallel for simd schedule(static) (same performance as below)
58 #pragma omp parallel for schedule(static)
59 for (register int j = 0; j < N; j++) a[j] = b[j] + scalar * c[j];
60 times[k] = MPI_Wtime() - times[k];
61 }
62 for (int k = 1; k < NTIMES; k++) { /* note -- skip first iteration */
63 mintime = MIN(mintime, times[k]);
64 }
65
66 if (size == 65) printf("Never printed %g\n", a[11]);
67 rate = 1.0E-06 * bytes / mintime;
68
69 if (size == 1) {
70 printf("%d %11.4f Rate (MB/s) 1\n", size, rate);
71 fd = fopen("flops", "w");
72 fprintf(fd, "%g\n", rate);
73 fclose(fd);
74 } else {
75 double prate;
76 fd = fopen("flops", "r");
77 fscanf(fd, "%lg", &prate);
78 fclose(fd);
79 printf("%d %11.4f Rate (MB/s) %g\n", size, rate, rate / prate);
80 }
81 MPI_Finalize();
82 return 0;
83 }
84