Update timing code to (maybe) be Mac compatible.

00-timing-soln.c

@@ -1,31 +1,19 @@
 #include <stdio.h>
-#include <time.h>
+#include "timing.h"
 
-double timespec_diff_in_seconds(struct timespec start, struct timespec end)
-{
-  struct timespec temp;
-  if ((end.tv_nsec-start.tv_nsec)<0) {
-    temp.tv_sec = end.tv_sec-start.tv_sec-1;
-    temp.tv_nsec = 1000000000+end.tv_nsec-start.tv_nsec;
-  } else {
-    temp.tv_sec = end.tv_sec-start.tv_sec;
-    temp.tv_nsec = end.tv_nsec-start.tv_nsec;
-  }
-  return temp.tv_sec + 1e-9*temp.tv_nsec;
-}
 
 int main()
 {
-  struct timespec time1, time2;
-  clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time1);
+  timestamp_type time1, time2;
+  get_timestamp(&time1);
 
   long int temp = 1;
   for (int i = 0; i< 250000000; i++)
     temp+= 3*temp-1;
 
-  clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &time2);
+  get_timestamp(&time2);
   printf("that took %f seconds\n",
-      timespec_diff_in_seconds(time1,time2));
+      timestamp_diff_in_seconds(time1,time2));
 
   // printf("and the result was %d\n", temp);
 

timing.h

@@ -1,48 +1,43 @@
-#include <time.h>
+#ifdef __APPLE__
 
-#ifdef __APPLE___
+#include <sys/time.h>
 
 typedef struct timeval timestamp_type;
 
-static void get_current_time(timestamp_type *t)
+static void get_timestamp(timestamp_type *t)
 {
-  gettimeofday(t);
+  gettimeofday(t, NULL);
 }
 
-double
-timeval_subtract (timestamp_type x, timestamp_type y)
+double timestamp_diff_in_seconds(timestamp_type x, timestamp_type y)
 {
   /* Perform the carry for the later subtraction by updating y. */
-  if (x.tv_usec < y->tv_usec) {
-    int nsec = (y->tv_usec - x.tv_usec) / 1000000 + 1;
-    y->tv_usec -= 1000000 * nsec;
-    y->tv_sec += nsec;
+  if (x.tv_usec < y.tv_usec) {
+    int nsec = (y.tv_usec - x.tv_usec) / 1000000 + 1;
+    y.tv_usec -= 1000000 * nsec;
+    y.tv_sec += nsec;
   }
-  if (x.tv_usec - y->tv_usec > 1000000) {
-    int nsec = (x.tv_usec - y->tv_usec) / 1000000;
-    y->tv_usec += 1000000 * nsec;
-    y->tv_sec -= nsec;
+  if (x.tv_usec - y.tv_usec > 1000000) {
+    int nsec = (x.tv_usec - y.tv_usec) / 1000000;
+    y.tv_usec += 1000000 * nsec;
+    y.tv_sec -= nsec;
   }
 
-  /* Compute the time remaining to wait.
-     tv_usec is certainly positive. */
-  result->tv_sec = x.tv_sec;
-  result->tv_usec = x.tv_usec - y->tv_usec;
-
-  /* Return 1 if result is negative. */
-  return x.tv_sec < y->tv_sec;
+  return x.tv_sec + (x.tv_usec - y.tv_usec)*1e-6;
 }
 
 #else
 
+#include <time.h>
+
 typedef struct timespec timestamp_type;
 
-static void get_current_time(timestamp_type *t)
+static void get_timestamp(timestamp_type *t)
 {
   clock_gettime(CLOCK_REALTIME, t);
 }
 
-static double timespec_diff_in_seconds(timestamp_type start, timestamp_type end)
+static double timestamp_diff_in_seconds(timestamp_type start, timestamp_type end)
 {
   struct timespec temp;
   if ((end.tv_nsec-start.tv_nsec)<0) {