Re: [Help-gsl] Questions about using gsl permutation

[John D Lamb]

On 15/02/14 22:38, Yi-Ping Huang wrote:
> I am trying to use gsl permutation. And I have a hard time to pass the
> information to the functions in permutation.

The manual could make it clearer that most functions, like 
gsl_permutation_swap(), gsl_permutation_next(), and gsl_permute(), work 
with the permutation in linear form. The canonical form is less usual. I 
mainly us it if I want t print the permutation in canonical form.

> For example, I would like to evaluate the number of cycles of a specific
> permutation [1023456789].
> If I store this integer series in the array a. How should I transform the
> information into gsl_permutation_linear_cycles?

int i, cycles;
gsl_permutation *p;
…

p = gsl_permutation_alloc( 10 );

for( i = 0; i < gsl_permutation_size( p ); ++i )
  gsl_permutation_data( p )[i] = a[i];

cycles = gsl_permutation_linear_cycles( p );

ought to do it. I would write a small test program and see that it gives 
the result I expect before using this.

--
John D Lamb