/* read a problem from a file; use %g for integers to avoid int conflicts */
problem *get_problem (FILE *f, double tol)
{
cs *T, *A, *C ;
int sym, m, n, mn, nz1, nz2 ;
problem *Prob ;
Prob = cs_calloc (1, sizeof (problem)) ;
if (!Prob) return (NULL) ;
T = cs_load (f) ; /* load triplet matrix T from a file */
Prob->A = A = cs_compress (T) ; /* A = compressed-column form of T */
cs_spfree (T) ; /* clear T */
if (!cs_dupl (A)) return (free_problem (Prob)) ; /* sum up duplicates */
Prob->sym = sym = is_sym (A) ; /* determine if A is symmetric */
m = A->m ; n = A->n ;
mn = CS_MAX (m,n) ;
nz1 = A->p [n] ;
cs_dropzeros (A) ; /* drop zero entries */
nz2 = A->p [n] ;
if (tol > 0) cs_droptol (A, tol) ; /* drop tiny entries (just to test) */
Prob->C = C = sym ? make_sym (A) : A ; /* C = A + triu(A,1)', or C=A */
if (!C) return (free_problem (Prob)) ;
printf ("\n--- Matrix: %g-by-%g, nnz: %g (sym: %g: nnz %g), norm: %8.2e\n",
(double) m, (double) n, (double) (A->p [n]), (double) sym,
(double) (sym ? C->p [n] : 0), cs_norm (C)) ;
if (nz1 != nz2) printf ("zero entries dropped: %g\n", (double) (nz1 - nz2));
if (nz2 != A->p [n]) printf ("tiny entries dropped: %g\n",
(double) (nz2 - A->p [n])) ;
Prob->b = cs_malloc (mn, sizeof (double)) ;
Prob->x = cs_malloc (mn, sizeof (double)) ;
Prob->resid = cs_malloc (mn, sizeof (double)) ;
return ((!Prob->b || !Prob->x || !Prob->resid) ? free_problem (Prob) : Prob) ;
}
/* cs_droptol: remove small entries from A */
void mexFunction
(
int nargout,
mxArray *pargout [ ],
int nargin,
const mxArray *pargin [ ]
)
{
cs Amatrix, *C, *A ;
int j, k ;
double tol ;
if (nargout > 1 || nargin != 2)
{
mexErrMsgTxt ("Usage: C = cs_droptol(A,tol)") ;
}
A = cs_mex_get_sparse (&Amatrix, 0, 1, pargin [0]) ; /* get A */
tol = mxGetScalar (pargin [1]) ; /* get tol */
C = cs_spalloc (A->m, A->n, A->nzmax, 1, 0) ; /* C = A */
for (j = 0 ; j <= A->n ; j++) C->p [j] = A->p [j] ;
for (k = 0 ; k < A->nzmax ; k++) C->i [k] = A->i [k] ;
for (k = 0 ; k < A->nzmax ; k++) C->x [k] = A->x [k] ;
cs_droptol (C, tol) ; /* drop from C */
pargout [0] = cs_mex_put_sparse (&C) ; /* return C */
}
