how to reduce page faults in this program?

Question

I'm gating more then 1000 page faults in this program. can i reduce them to some smaller value or even to zero ? or even any other changes can speed up the execution

#include <stdio.h>
#include<stdlib.h>
int main(int argc, char* argv[])
{
  register unsigned  int u, v,i;
  register unsigned int arr_size=0;
  register unsigned int b_size=0;
  register unsigned  int c;
  register unsigned  int *b;
  FILE *file;
  register unsigned int *arr;
  file=fopen(argv[1],"r");
  arr=(unsigned int *)malloc(4*10000000);
  while(!feof(file)){
    ++arr_size;
    fscanf(file,"%u\n",&arr[arr_size-1]);
  }
  fclose(file);
  b=(unsigned int *)malloc(arr_size*4);
  if (arr_size!=0)
  {
    ++b_size;
    b[b_size-1]=0;

    for (i = 1; i < arr_size; ++i)
    {
      if (arr[b[b_size-1]] < arr[i])
      {
        ++b_size;
        b[b_size-1]=i;
        continue;
      }
      for (u = 0, v = b_size-1; u < v;)
      {
        c = (u + v) / 2;
        if (arr[b[c]] < arr[i]) u=c+1; else v=c;
      }
      if (arr[i] < arr[b[u]])
      {
        b[u] = i;
      }
      if(i>arr_size)break;
    }
  }
  free(arr);
  free(b);
  printf("%u\n", b_size);
  return 0;
}

A first thing you could do to improve your program would be proper indenting. Wait, I'll edit that for you. — schnaader, Aug 19 '11 at 18:48
You get a lot of page faults because you use a lot of memory. That's the way the operating system works, turning virtual memory into real memory. — Hans Passant, Aug 19 '11 at 20:16

score 0 · Answer 1 · answered Aug 19 '11 at 19:02

0

The line:

arr=(unsigned int *)malloc(4*10000000);

is not a good programming style. Are you sure that your file is as big as 40MBs? try not to allocate the whole memory in the first lines of your program.

answered Aug 19 '11 at 19:02

TonySalimi

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i tried to use realloc() but it slowing down the program. i made but thank you my file may cost 15MB so i changed it to 4*3750000 – R Krishna Sagar Aug 19 '11 at 19:25

how to reduce page faults in this program?

1 Answers1