[Help-gsl] Declaring GSL Matrices

[Matthew Boulton]

Hello. I'm having a bit of an issue with implementing GSL matrices. 
Basically at the moment when I declare a permutation matrix in a 
particular function called by the main function, that matrix is not 
considered to be declared if I try and use it later on in my main function.

For example, I declare a matrix called indx in check_stamps() as follows:

 gsl_permutation * indx = gsl_permutation_calloc( ncomp_total + 1 + 100 );

Now bear in mind that line is in the check_stamps() function, my main 
function looks as follows:

 check_stamps();
 printf("Expanding Matrix\n");
 mat_size = (ncomp_kernel - 1) * ((( deg_spatial + 1 ) * ( deg_spatial 
+ 2 )) / 2) + ((( deg_bg + 1 ) * ( deg_bg + 2 )) / 2) + 1;
 gsl_matrix *matrix = gsl_matrix_calloc( ncomp_total + 1 + 100 , 
ncomp_total + 1 + 100);   /* Declare matrix */
 matrix = build_matrix();
 printf("Expanding Matrix Done\n");
 build_scprod(sub_image);
 ncomp_total = (ncomp1 - 1) * ncomp2 + 1 + ncomp_bg; /* = mat_size 
(Size of matrix) */
/* gsl_permutation *indx = gsl_permutation_calloc( ncomp_total + 1 + 100 
);  Has same dimension as 'matrix' but is 1D */
 gsl_linalg_LU_decomp( matrix , indx , d );

Sadly this will not compile unless I remove the commented out line, but 
this means I am declaring the same matrix twice.

Is this a common problem or have I simply not implemented this correctly?

Kind Regards,

Matt