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/* ========================================================================== */
/* === CHOLMOD/MATLAB/Test/lxbpattern mexFunction =========================== */
/* ========================================================================== */
/* -----------------------------------------------------------------------------
* CHOLMOD/MATLAB Module. Copyright (C) 2005-2013, Timothy A. Davis
* http://www.suitesparse.com
* MATLAB(tm) is a Trademark of The MathWorks, Inc.
* -------------------------------------------------------------------------- */
/* Find the nonzero pattern of x=L\b for a sparse vector b. If numerical
* cancellation has caused entries to drop in L, then this function may
* give an incorrect result.
*
* xpattern = lxbpattern (L,b), same as xpattern = find (L\b),
* assuming no numerical cancellation, except that xpattern will not
* appear in sorted ordering (it appears in topological ordering).
*
* The core cholmod_lsolve_pattern function takes O(length (xpattern)) time,
* except that the initialzations in this mexFunction interface add O(n) time.
*
* This function is for testing cholmod_lsolve_pattern only.
*/
#include "cholmod_matlab.h"
void mexFunction
(
int nargout,
mxArray *pargout [ ],
int nargin,
const mxArray *pargin [ ]
)
{
double dummy = 0 ;
Long *Lp, *Lnz, *Xp, *Xi, xnz ;
cholmod_sparse *B, Bmatrix, *X ;
cholmod_factor *L ;
cholmod_common Common, *cm ;
Long j, n ;
/* ---------------------------------------------------------------------- */
/* start CHOLMOD and set parameters */
/* ---------------------------------------------------------------------- */
cm = &Common ;
cholmod_l_start (cm) ;
sputil_config (SPUMONI, cm) ;
/* ---------------------------------------------------------------------- */
/* check inputs */
/* ---------------------------------------------------------------------- */
if (nargin != 2 || nargout > 1)
{
mexErrMsgTxt ("usage: xpattern = lxbpattern (L,b)") ;
}
n = mxGetN (pargin [0]) ;
if (!mxIsSparse (pargin [0]) || n != mxGetM (pargin [0]))
{
mexErrMsgTxt ("lxbpattern: L must be sparse and square") ;
}
if (n != mxGetM (pargin [1]) || mxGetN (pargin [1]) != 1)
{
mexErrMsgTxt ("lxbpattern: b wrong dimension") ;
}
if (!mxIsSparse (pargin [1]))
{
mexErrMsgTxt ("lxbpattern: b must be sparse") ;
}
/* ---------------------------------------------------------------------- */
/* get the sparse b */
/* ---------------------------------------------------------------------- */
/* get sparse matrix B (unsymmetric) */
B = sputil_get_sparse (pargin [1], &Bmatrix, &dummy, 0) ;
/* ---------------------------------------------------------------------- */
/* construct a shallow copy of the input sparse matrix L */
/* ---------------------------------------------------------------------- */
/* the construction of the CHOLMOD takes O(n) time and memory */
/* allocate the CHOLMOD symbolic L */
L = cholmod_l_allocate_factor (n, cm) ;
L->ordering = CHOLMOD_NATURAL ;
/* get the MATLAB L */
L->p = mxGetJc (pargin [0]) ;
L->i = mxGetIr (pargin [0]) ;
L->x = mxGetPr (pargin [0]) ;
L->z = mxGetPi (pargin [0]) ;
/* allocate and initialize the rest of L */
L->nz = cholmod_l_malloc (n, sizeof (Long), cm) ;
Lp = L->p ;
Lnz = L->nz ;
for (j = 0 ; j < n ; j++)
{
Lnz [j] = Lp [j+1] - Lp [j] ;
}
/* L is not truly a valid CHOLMOD sparse factor, since L->prev and next are
NULL. But these pointers are not accessed in cholmod_lsolve_pattern */
L->prev = NULL ;
L->next = NULL ;
L->xtype = (mxIsComplex (pargin [0])) ? CHOLMOD_ZOMPLEX : CHOLMOD_REAL ;
L->nzmax = Lp [n] ;
/* ---------------------------------------------------------------------- */
/* allocate size-n space for the result X */
/* ---------------------------------------------------------------------- */
X = cholmod_l_allocate_sparse (n, 1, n, FALSE, TRUE, 0, 0, cm) ;
/* ---------------------------------------------------------------------- */
/* find the pattern of X=L\B */
/* ---------------------------------------------------------------------- */
cholmod_l_lsolve_pattern (B, L, X, cm) ;
/* ---------------------------------------------------------------------- */
/* return result, converting to 1-based */
/* ---------------------------------------------------------------------- */
Xp = (Long *) X->p ;
Xi = (Long *) X->i ;
xnz = Xp [1] ;
pargout [0] = sputil_put_int (Xi, xnz, 1) ;
/* ---------------------------------------------------------------------- */
/* free workspace and the CHOLMOD L, except for what is copied to MATLAB */
/* ---------------------------------------------------------------------- */
L->p = NULL ;
L->i = NULL ;
L->x = NULL ;
L->z = NULL ;
cholmod_l_free_factor (&L, cm) ;
cholmod_l_free_sparse (&X, cm) ;
cholmod_l_finish (cm) ;
cholmod_l_print_common (" ", cm) ;
}
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