#define SIZE 10000000
int x[SIZE];
int y[SIZE];
int i;
int *p1, *p2;

void TestSubscripts(void)
{
  for (i = 0; i < SIZE; i++)
    x[i] = y[i];
}

void TestPointers1(void)
{
  for (p1 = x, p2 = y; p1 - x < SIZE; )
    *p1++ = *p2++;
}

void TestPointers2(void)
{
  for (p1 = x, p2 = y; p1 < &x[SIZE]; )
    *p1++ = *p2++;
}

void TestPointers3(void)
{
  register int *p1, *p2;

  for (p1 = x, p2 = y; p1 < &x[SIZE]; )
    *p1++ = *p2++;
}

void TestTimings(void)
{
  void (*tests[])(void) = {TestSubscripts, TestPointers1, TestPointers2, TestPointers3, TestPointers4};

  #define NUM (sizeof(tests) / sizeof(*tests))

  clock_t start[NUM + 1] = {0};
  clock_t end[NUM + 1]   = {0};
  clock_t total[NUM + 1] = {0};
  int i, j;
  int iterations = 10;

    /* don't count the first iteration, let the cache stabilize */
  for (i = 0; i <= iterations; i++)
  {
    for (j = 0; j < NUM; j++)
    {
      start[j] = clock();
      tests[j]();
      end[j] = clock();

      if (i) /* skip first one */
        total[j] += end[j] - start[j];
    }
 
    if (i) /* skip first */
    {
      printf("%2i:  ", i);
      for (j = 0 ; j < NUM; j++)
        printf("test%i = %3li  ", j + 1, end[j] - start[j]);
      printf("\n");
    }
  }
  
  printf("\nAve: ");
  for (j = 0; j < NUM; j++)
    printf("test%i = %3li  ", j + 1, total[j] / iterations);
  printf("\n");
}

void TestTimings(void)
{
  void (*tests[])(void) = {TestSubscripts, TestPointers1, TestPointers2, TestPointers3, TestPointers4};
  void (**pf)(void);

  #define NUM (sizeof(tests) / sizeof(*tests))

  clock_t start[NUM + 1] = {0};
  clock_t end[NUM + 1]   = {0};
  clock_t total[NUM + 1] = {0};
  int i, j;
  int iterations = 10;

    /* don't count the first iteration, let the cache stabilize */
  for (i = 0; i <= iterations; i++)
  {
    pf = tests;
    for (j = 0; j < NUM; j++)
    {
      start[j] = clock();
      (*pf++)();
      end[j] = clock();

      if (i) /* skip first one */
        total[j] += end[j] - start[j];
    }
 
    if (i) /* skip first */
    {
      printf("%2i:  ", i);
      for (j = 0 ; j < NUM; j++)
        printf("test%i = %3li  ", j + 1, end[j] - start[j]);
      printf("\n");
    }
  }
  
  printf("\nAve: ");
  for (j = 0; j < NUM; j++)
    printf("test%i = %3li  ", j + 1, total[j] / iterations);
  printf("\n");
}