in reply to Re^2: Odometer pattern iterator (in C).
in thread Odometer pattern iterator (in C). (Updated.)

A chance to brush off my C :) 

// inc_c - http://perlmonks.org/?node_id=1128230

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

#define M 5 // place
#define N 3 // number of elements wanted

static int place[N];

int
step(void)
  {
  for(int i = 0; i < N; i++)
    {
    if(i < N - 1 ? place[i] < place[i + 1] - 1 : place[i] < M - 1 )
      {
      place[i]++;
      for(int j = i - 1; j >= 0; j--) place[j] -= 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;

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

  exit(0);
  }

[download]

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Re^4: Odometer pattern iterator (in C).
by BrowserUk (Patriarch) on May 29, 2015 at 16:43 UTC

    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.

    With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority". I'm with torvalds on this
    In the absence of evidence, opinion is indistinguishable from prejudice. Agile (and TDD) debunked
[reply]
[d/l]

      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]
[reply]
[d/l]

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

        With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
        Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
        "Science is about questioning the status quo. Questioning authority". I'm with torvalds on this
        In the absence of evidence, opinion is indistinguishable from prejudice. Agile (and TDD) debunked
[reply]

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