That works. But it's about 40% slower than the A::C version I nicked. 11 seconds instead of 8 for the 601 million 16 from 32:

[17:27:38.79] C:\test\humanGenome>junk 32 16
^C
[17:41:10.28] C:\test\humanGenome>junk 32 16
Iters:601080390

[17:41:17.49] C:\test\humanGenome>junk2 32 16
^C
[17:41:40.82] C:\test\humanGenome>junk2 32 16
Iters:601080390

[17:41:52.30] C:\test\humanGenome>
[download]

junk2 is your code adapted to count rather than print.

I'm still brushing the rust off my C. :) This one is 50% faster with only slight tweaks. This tight loop is *highly* sensitive to almost any change. BTW, going from -o2 to -o4 doubles speed.

// inc_c - http://perlmonks.org/?node_id=1128230
// 8.52 secs. for 16/32 count=601080390 -o2
// 3.16 secs. for 16/32 count=601080390 -o4

#include <stdlib.h>
#include <stdio.h>

#define N 16 // number of elements wanted
#define M 32 // place

static int place[N+1];
static int count = 0;

int
step(void)
  {
  int *p = place;

  for(int i = 0; i < N; i++, p++ )
    {
    if(*p < p[1] - 1)
      {
      ++*p;
      while( --i >= 0 ) *--p -= place[0];
      return 1;
      }
    }
  return 0;
  }

int
main(int argc, char **argv)
  {
  int i;
  int more = 1;

  for(i = 0; i < N; i++) place[i] = i;
  place[N] = M;

  while( more )
    {
    //for(i = 0; i < N; i++) printf(" %d", place[i]);
    //putchar('\n');
    count++;
    more = step();
    }

  printf("%d\n", count);

  exit(0);
  }
[download]

Yes. That now beats the A::C version by about 20% (6.5s v 8) on my system when compiled with /Ox. Thank you.

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