Create benchmark.c

benchmark.c

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+// test memory access time by "touching" elements of a linear array A
+// with a progressively growing stepsize (stride).
+//
+// Author : Yuhua Ma (ym474)
+// Date : 2/1/2020
+// How to compile :
+//
+// % cd _sourcefile's path_
+// % gcc -o benchmark benchmark.c
+//
+// no std=c99 because clock_gettime()
+// add -pthread because pthread_create,pthread_join
+// % ./benchmark
+//
+// #include <math.h> //pow()
+#include <stdio.h>  //printf
+#include <stdlib.h> // malloc
+#include <time.h>   /* for clock_gettime */
+#include <stdint.h> /* for uint64 definition */
+
+#define BILLION 1E9L
+#define MAX_LENGTH1 1 << 26
+#define MIN_SIZE1 1 << 10
+
+void main() {
+  struct timespec start, end;
+  double diff;
+  float *A = (float *)malloc(sizeof(float) * MAX_LENGTH1); // whether init A[][]
+                                                           // does not influence
+                                                           // the experiment
+                                                           // result
+
+  int n, s, i, c, cnt = 10, tmp, j;
+
+  FILE *f = fopen("problem1_data.txt", "w");
+
+  for (n = MIN_SIZE1; n <= MAX_LENGTH1; n *= 2) {
+    fprintf(f, "n = %ld\n", n);
+    for (s = 1; s <= n / 2; s *= 2) {
+      clock_gettime(CLOCK_MONOTONIC, &start);
+      for (c = 0; c < cnt * s; c++) {
+        for (i = 0; i < n; i += s) {
+          tmp = A[i]; // load A[i]
+        }
+      }
+      clock_gettime(CLOCK_MONOTONIC, &end);
+      diff =
+          BILLION * (end.tv_sec - start.tv_sec) + end.tv_nsec - start.tv_nsec;
+      diff = diff / (n * cnt);
+      printf("array length(n) : %ld stride length(s) : %ld for s*n times. "
+             "Average timing(sec) %llu\n",
+             n, s, diff);
+      fprintf(f, "%lf\n", diff);
+    }
+    fprintf(f, "------------------\n");
+  }
+  fclose(f);
+}