Initial data commit

Task/Time-a-function/C/time-a-function.c

@@ -0,0 +1,39 @@
+#include <stdio.h>
+#include <time.h>
+
+int identity(int x) { return x; }
+
+int sum(int s)
+{
+  int i;
+  for(i=0; i < 1000000; i++) s += i;
+  return s;
+}
+
+#ifdef CLOCK_PROCESS_CPUTIME_ID
+/* cpu time in the current process */
+#define CLOCKTYPE  CLOCK_PROCESS_CPUTIME_ID
+#else
+/* this one should be appropriate to avoid errors on multiprocessors systems */
+#define CLOCKTYPE  CLOCK_MONOTONIC
+#endif
+
+double time_it(int (*action)(int), int arg)
+{
+  struct timespec tsi, tsf;
+
+  clock_gettime(CLOCKTYPE, &tsi);
+  action(arg);
+  clock_gettime(CLOCKTYPE, &tsf);
+
+  double elaps_s = difftime(tsf.tv_sec, tsi.tv_sec);
+  long elaps_ns = tsf.tv_nsec - tsi.tv_nsec;
+  return elaps_s + ((double)elaps_ns) / 1.0e9;
+}
+
+int main()
+{
+  printf("identity (4) takes %lf s\n", time_it(identity, 4));
+  printf("sum      (4) takes %lf s\n", time_it(sum, 4));
+  return 0;
+}