Re: [Help-gsl] GSL Implementation of Quick Sort (or something better)

[Patrick Alken]

why not use the qsort(3) function?

if you have a gsl_vector *v:

qsort(v->data, v->size, sizeof(double), &compare)

where you would just have to write the compare function.

On Thu, Aug 16, 2007 at 05:10:00PM +0100, Matthew Boulton wrote:
> Hello. I've got some quick sort code that is now reading in data from 
> GSl vectors, and so I was wondering if there is a GSL implementation of 
> the quick sort algorithm given below:
> 
> --quick_sort.c
> 
> #include "common.h"
> 
> void quick_sort (DATA_TYPE *list, int *index, int n){
> 
>  int i;
>  void quick_sort_1();
> 
>  for ( i = 0; i < n; i++ ) index [i]=i;
>  quick_sort_1 ( list , index , 0 , n-1 );
> 
>  return;
> 
> }
> 
> -- quick_sort_1.c
> 
> #include "common.h"
> 
> void quick_sort_1(DATA_TYPE *list, int *index, int left_end, int right_end)
> 
> {
> 
>  int i, j, temp;
>  DATA_TYPE chosen;
> 
>  chosen = list[ index[ (left_end + right_end) / 2 ] ];
>  i = (left_end - 1);
>  j = (right_end + 1);
> 
>  for (;;)
> 
>    {
>  
>    while (list [index[++i]] < chosen);
>    while (list [index[--j]] > chosen);
>   
>    if (i < j)
> 
>      {
>     
>         temp = index [j];
>         index [j] = index [i];
>         index [i] = temp;
>     
>      }
> 
>    else if (i==j)
> 
>      {
> 
>      ++i;
>      break;
>   
>      }
>   
>    else break;
>  
>  }
> 
>  if (left_end < j)  quick_sort_1 (list, index, left_end, j);
>  if (i < right_end) quick_sort_1 (list, index, i, right_end);
> 
>  return;
>   
> }
> 
> which looks like a fairly standard quick sort algorithm. If there is no 
> GSL quick sort algorithm, then would the GSL heapsort algorithm easily 
> take the place of the above quick sort  function?
> 
> Kind Regards,
> 
> Matt
> 
> 
> 
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