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/* ========================================================================== */
/* === CHOLMOD/MATLAB/ldlsolve mexFunction ================================== */
/* ========================================================================== */
/* -----------------------------------------------------------------------------
* CHOLMOD/MATLAB Module. Copyright (C) 2005-2006, Timothy A. Davis
* http://www.suitesparse.com
* MATLAB(tm) is a Trademark of The MathWorks, Inc.
* -------------------------------------------------------------------------- */
/* Solve LDL'x=b given an LDL' factorization computed by ldlchol.
*
* Usage:
*
* x = ldlsolve (LD,b)
*
* b can be dense or sparse.
*/
#include "cholmod_matlab.h"
void mexFunction
(
int nargout,
mxArray *pargout [ ],
int nargin,
const mxArray *pargin [ ]
)
{
double dummy = 0, rcond ;
Long *Lp, *Lnz, *Lprev, *Lnext ;
cholmod_sparse *Bs, Bspmatrix, *Xs ;
cholmod_dense *B, Bmatrix, *X ;
cholmod_factor *L ;
cholmod_common Common, *cm ;
Long j, k, n, B_is_sparse, head, tail ;
/* ---------------------------------------------------------------------- */
/* start CHOLMOD and set parameters */
/* ---------------------------------------------------------------------- */
cm = &Common ;
cholmod_l_start (cm) ;
sputil_config (SPUMONI, cm) ;
/* ---------------------------------------------------------------------- */
/* check inputs */
/* ---------------------------------------------------------------------- */
if (nargout > 1 || nargin != 2)
{
mexErrMsgTxt ("Usage: x = ldlsolve (LD, b)") ;
}
n = mxGetN (pargin [0]) ;
k = mxGetN (pargin [1]) ;
if (!mxIsSparse (pargin [0]) || n != mxGetM (pargin [0]))
{
mexErrMsgTxt ("ldlsolve: LD must be sparse and square") ;
}
if (n != mxGetM (pargin [1]))
{
mexErrMsgTxt ("ldlsolve: b wrong dimension") ;
}
/* ---------------------------------------------------------------------- */
/* get b */
/* ---------------------------------------------------------------------- */
/* get sparse or dense matrix B */
B = NULL ;
Bs = NULL ;
B_is_sparse = mxIsSparse (pargin [1]) ;
if (B_is_sparse)
{
/* get sparse matrix B (unsymmetric) */
Bs = sputil_get_sparse (pargin [1], &Bspmatrix, &dummy, 0) ;
}
else
{
/* get dense matrix B */
B = sputil_get_dense (pargin [1], &Bmatrix, &dummy) ;
}
/* ---------------------------------------------------------------------- */
/* 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->prev = cholmod_l_malloc (n+2, sizeof (Long), cm) ;
L->next = cholmod_l_malloc (n+2, sizeof (Long), cm) ;
Lprev = L->prev ;
Lnext = L->next ;
head = n+1 ;
tail = n ;
Lnext [head] = 0 ;
Lprev [head] = -1 ;
Lnext [tail] = -1 ;
Lprev [tail] = n-1 ;
for (j = 0 ; j < n ; j++)
{
Lnext [j] = j+1 ;
Lprev [j] = j-1 ;
}
Lprev [0] = head ;
L->xtype = (mxIsComplex (pargin [0])) ? CHOLMOD_ZOMPLEX : CHOLMOD_REAL ;
L->nzmax = Lp [n] ;
/* ---------------------------------------------------------------------- */
/* solve and return solution to MATLAB */
/* ---------------------------------------------------------------------- */
if (B_is_sparse)
{
/* solve LDL'X=B with sparse X and B; return sparse X to MATLAB */
Xs = cholmod_l_spsolve (CHOLMOD_LDLt, L, Bs, cm) ;
pargout [0] = sputil_put_sparse (&Xs, cm) ;
}
else
{
/* solve AX=B with dense X and B; return dense X to MATLAB */
X = cholmod_l_solve (CHOLMOD_LDLt, L, B, cm) ;
pargout [0] = sputil_put_dense (&X, cm) ;
}
rcond = cholmod_l_rcond (L, cm) ;
if (rcond == 0)
{
mexWarnMsgTxt ("Matrix is indefinite or singular to working precision");
}
else if (rcond < DBL_EPSILON)
{
mexWarnMsgTxt ("Matrix is close to singular or badly scaled.") ;
mexPrintf (" Results may be inaccurate. RCOND = %g.\n", rcond) ;
}
/* ---------------------------------------------------------------------- */
/* 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_finish (cm) ;
cholmod_l_print_common (" ", cm) ;
/*
if (cm->malloc_count !=
(mxIsComplex (pargout [0]) + (mxIsSparse (pargout[0]) ? 3:1)))
mexErrMsgTxt ("!") ;
*/
}
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