Re: [Help-gsl] gsl_linalg_LU_decomp Function

[Matthew Boulton]

> > Basically I have a matrix called 'matrix' and a permutation matrix called
> > 'indx', both of which are of length mat_size + 1 (except that 'matrix' is in 2D
> > of course so it has two columns of that length). However, GCC flags up an error
> > when I run the code saying:
> >
> > gsl: lu.c:67: ERROR: permutation length must match matrix size
> >     
>
> Could we see a code snippet? Do you have a gsl_matrix that happens to
> be a permutation matrix or a gsl_permutation?
>
> - Jordi G. H.
>   

The programme is far too large to post here I'm afraid, but hopefully 
this snippet will be of use:


 gsl_matrix *matrix = gsl_matrix_calloc( mat_size + 1 , mat_size + 1 ); 
       /* Declare matrix */

 ncomp_total = ( (ncomp1 - 1) * ncomp2 ) + 1 + ncomp_bg; /* = mat_size 
(Size of matrix) */

 gsl_permutation *indx = gsl_permutation_calloc( ncomp_total + 1 ); /* 
Has same length as 'matrix' but is 1D */
 gsl_permutation_init(indx);
 gsl_linalg_LU_decomp( matrix , indx , d ); /* 'matrix' and 'indx' are 
the same size! */


So to answer your last question I have specifically initialised indx 
using gsl_permutation.

Kind Regards,

Matt