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/*
* -- SuperLU routine (version 2.0) --
* Univ. of California Berkeley, Xerox Palo Alto Research Center,
* and Lawrence Berkeley National Lab.
* November 15, 1997
*
*/
/*
Copyright (c) 2003, The Regents of the University of California, through
Lawrence Berkeley National Laboratory (subject to receipt of any required
approvals from U.S. Dept. of Energy)
All rights reserved.
The source code is distributed under BSD license, see the file License.txt
*/
/*
Copyright (c) 1997 by Xerox Corporation. All rights reserved.
THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
EXPRESSED OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
Permission is hereby granted to use or copy this program for any
purpose, provided the above notices are retained on all copies.
Permission to modify the code and to distribute modified code is
granted, provided the above notices are retained, and a notice that
the code was modified is included with the above copyright notice.
*/
#include <math.h>
#include "slu_ddefs.h"
double
dPivotGrowth(int ncols, SuperMatrix *A, int *perm_c,
SuperMatrix *L, SuperMatrix *U)
{
/*
* Purpose
* =======
*
* Compute the reciprocal pivot growth factor of the leading ncols columns
* of the matrix, using the formula:
* min_j ( max_i(abs(A_ij)) / max_i(abs(U_ij)) )
*
* Arguments
* =========
*
* ncols (input) int
* The number of columns of matrices A, L and U.
*
* A (input) SuperMatrix*
* Original matrix A, permuted by columns, of dimension
* (A->nrow, A->ncol). The type of A can be:
* Stype = NC; Dtype = SLU_D; Mtype = GE.
*
* L (output) SuperMatrix*
* The factor L from the factorization Pr*A=L*U; use compressed row
* subscripts storage for supernodes, i.e., L has type:
* Stype = SC; Dtype = SLU_D; Mtype = TRLU.
*
* U (output) SuperMatrix*
* The factor U from the factorization Pr*A*Pc=L*U. Use column-wise
* storage scheme, i.e., U has types: Stype = NC;
* Dtype = SLU_D; Mtype = TRU.
*
*/
NCformat *Astore;
SCformat *Lstore;
NCformat *Ustore;
double *Aval, *Lval, *Uval;
int fsupc, nsupr, luptr, nz_in_U;
int i, j, k, oldcol;
int *inv_perm_c;
double rpg, maxaj, maxuj;
extern double dlamch_(char *);
double smlnum;
double *luval;
/* Get machine constants. */
smlnum = dlamch_("S");
rpg = 1. / smlnum;
Astore = A->Store;
Lstore = L->Store;
Ustore = U->Store;
Aval = Astore->nzval;
Lval = Lstore->nzval;
Uval = Ustore->nzval;
inv_perm_c = (int *) SUPERLU_MALLOC(A->ncol*sizeof(int));
for (j = 0; j < A->ncol; ++j) inv_perm_c[perm_c[j]] = j;
for (k = 0; k <= Lstore->nsuper; ++k) {
fsupc = L_FST_SUPC(k);
nsupr = L_SUB_START(fsupc+1) - L_SUB_START(fsupc);
luptr = L_NZ_START(fsupc);
luval = &Lval[luptr];
nz_in_U = 1;
for (j = fsupc; j < L_FST_SUPC(k+1) && j < ncols; ++j) {
maxaj = 0.;
oldcol = inv_perm_c[j];
for (i = Astore->colptr[oldcol]; i < Astore->colptr[oldcol+1]; ++i)
maxaj = SUPERLU_MAX( maxaj, fabs(Aval[i]) );
maxuj = 0.;
for (i = Ustore->colptr[j]; i < Ustore->colptr[j+1]; i++)
maxuj = SUPERLU_MAX( maxuj, fabs(Uval[i]) );
/* Supernode */
for (i = 0; i < nz_in_U; ++i)
maxuj = SUPERLU_MAX( maxuj, fabs(luval[i]) );
++nz_in_U;
luval += nsupr;
if ( maxuj == 0. )
rpg = SUPERLU_MIN( rpg, 1.);
else
rpg = SUPERLU_MIN( rpg, maxaj / maxuj );
}
if ( j >= ncols ) break;
}
SUPERLU_FREE(inv_perm_c);
return (rpg);
}
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