461 lines
15 KiB
C
461 lines
15 KiB
C
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/*! @file zgsrfs.c
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* \brief Improves computed solution to a system of inear equations
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*
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* <pre>
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* -- SuperLU routine (version 3.0) --
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* Univ. of California Berkeley, Xerox Palo Alto Research Center,
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* and Lawrence Berkeley National Lab.
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* October 15, 2003
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*
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* Modified from lapack routine ZGERFS
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* </pre>
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*/
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/*
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* File name: zgsrfs.c
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* History: Modified from lapack routine ZGERFS
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*/
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#include <math.h>
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#include "slu_zdefs.h"
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/*! \brief
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*
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* <pre>
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* Purpose
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* =======
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*
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* ZGSRFS improves the computed solution to a system of linear
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* equations and provides error bounds and backward error estimates for
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* the solution.
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*
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* If equilibration was performed, the system becomes:
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* (diag(R)*A_original*diag(C)) * X = diag(R)*B_original.
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*
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* See supermatrix.h for the definition of 'SuperMatrix' structure.
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*
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* Arguments
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* =========
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*
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* trans (input) trans_t
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* Specifies the form of the system of equations:
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* = NOTRANS: A * X = B (No transpose)
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* = TRANS: A'* X = B (Transpose)
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* = CONJ: A**H * X = B (Conjugate transpose)
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*
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* A (input) SuperMatrix*
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* The original matrix A in the system, or the scaled A if
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* equilibration was done. The type of A can be:
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* Stype = SLU_NC, Dtype = SLU_Z, Mtype = SLU_GE.
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*
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* L (input) SuperMatrix*
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* The factor L from the factorization Pr*A*Pc=L*U. Use
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* compressed row subscripts storage for supernodes,
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* i.e., L has types: Stype = SLU_SC, Dtype = SLU_Z, Mtype = SLU_TRLU.
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*
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* U (input) SuperMatrix*
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* The factor U from the factorization Pr*A*Pc=L*U as computed by
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* zgstrf(). Use column-wise storage scheme,
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* i.e., U has types: Stype = SLU_NC, Dtype = SLU_Z, Mtype = SLU_TRU.
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*
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* perm_c (input) int*, dimension (A->ncol)
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* Column permutation vector, which defines the
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* permutation matrix Pc; perm_c[i] = j means column i of A is
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* in position j in A*Pc.
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*
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* perm_r (input) int*, dimension (A->nrow)
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* Row permutation vector, which defines the permutation matrix Pr;
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* perm_r[i] = j means row i of A is in position j in Pr*A.
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*
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* equed (input) Specifies the form of equilibration that was done.
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* = 'N': No equilibration.
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* = 'R': Row equilibration, i.e., A was premultiplied by diag(R).
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* = 'C': Column equilibration, i.e., A was postmultiplied by
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* diag(C).
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* = 'B': Both row and column equilibration, i.e., A was replaced
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* by diag(R)*A*diag(C).
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*
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* R (input) double*, dimension (A->nrow)
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* The row scale factors for A.
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* If equed = 'R' or 'B', A is premultiplied by diag(R).
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* If equed = 'N' or 'C', R is not accessed.
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*
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* C (input) double*, dimension (A->ncol)
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* The column scale factors for A.
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* If equed = 'C' or 'B', A is postmultiplied by diag(C).
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* If equed = 'N' or 'R', C is not accessed.
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*
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* B (input) SuperMatrix*
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* B has types: Stype = SLU_DN, Dtype = SLU_Z, Mtype = SLU_GE.
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* The right hand side matrix B.
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* if equed = 'R' or 'B', B is premultiplied by diag(R).
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*
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* X (input/output) SuperMatrix*
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* X has types: Stype = SLU_DN, Dtype = SLU_Z, Mtype = SLU_GE.
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* On entry, the solution matrix X, as computed by zgstrs().
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* On exit, the improved solution matrix X.
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* if *equed = 'C' or 'B', X should be premultiplied by diag(C)
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* in order to obtain the solution to the original system.
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*
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* FERR (output) double*, dimension (B->ncol)
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* The estimated forward error bound for each solution vector
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* X(j) (the j-th column of the solution matrix X).
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* If XTRUE is the true solution corresponding to X(j), FERR(j)
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* is an estimated upper bound for the magnitude of the largest
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* element in (X(j) - XTRUE) divided by the magnitude of the
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* largest element in X(j). The estimate is as reliable as
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* the estimate for RCOND, and is almost always a slight
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* overestimate of the true error.
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*
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* BERR (output) double*, dimension (B->ncol)
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* The componentwise relative backward error of each solution
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* vector X(j) (i.e., the smallest relative change in
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* any element of A or B that makes X(j) an exact solution).
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*
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* stat (output) SuperLUStat_t*
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* Record the statistics on runtime and floating-point operation count.
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* See util.h for the definition of 'SuperLUStat_t'.
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*
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* info (output) int*
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* = 0: successful exit
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* < 0: if INFO = -i, the i-th argument had an illegal value
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*
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* Internal Parameters
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* ===================
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*
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* ITMAX is the maximum number of steps of iterative refinement.
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*
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* </pre>
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*/
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void
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zgsrfs(trans_t trans, SuperMatrix *A, SuperMatrix *L, SuperMatrix *U,
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int *perm_c, int *perm_r, char *equed, double *R, double *C,
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SuperMatrix *B, SuperMatrix *X, double *ferr, double *berr,
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SuperLUStat_t *stat, int *info)
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{
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#define ITMAX 5
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/* Table of constant values */
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int ione = 1;
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doublecomplex ndone = {-1., 0.};
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doublecomplex done = {1., 0.};
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/* Local variables */
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NCformat *Astore;
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doublecomplex *Aval;
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SuperMatrix Bjcol;
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DNformat *Bstore, *Xstore, *Bjcol_store;
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doublecomplex *Bmat, *Xmat, *Bptr, *Xptr;
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int kase;
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double safe1, safe2;
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int i, j, k, irow, nz, count, notran, rowequ, colequ;
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int ldb, ldx, nrhs;
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double s, xk, lstres, eps, safmin;
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char transc[1];
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trans_t transt;
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doublecomplex *work;
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double *rwork;
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int *iwork;
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extern int zlacon_(int *, doublecomplex *, doublecomplex *, double *, int *);
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#ifdef _CRAY
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extern int CCOPY(int *, doublecomplex *, int *, doublecomplex *, int *);
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extern int CSAXPY(int *, doublecomplex *, doublecomplex *, int *, doublecomplex *, int *);
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#else
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extern int zcopy_(int *, doublecomplex *, int *, doublecomplex *, int *);
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extern int zaxpy_(int *, doublecomplex *, doublecomplex *, int *, doublecomplex *, int *);
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#endif
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Astore = A->Store;
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Aval = Astore->nzval;
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Bstore = B->Store;
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Xstore = X->Store;
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Bmat = Bstore->nzval;
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Xmat = Xstore->nzval;
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ldb = Bstore->lda;
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ldx = Xstore->lda;
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nrhs = B->ncol;
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/* Test the input parameters */
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*info = 0;
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notran = (trans == NOTRANS);
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if ( !notran && trans != TRANS && trans != CONJ ) *info = -1;
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else if ( A->nrow != A->ncol || A->nrow < 0 ||
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A->Stype != SLU_NC || A->Dtype != SLU_Z || A->Mtype != SLU_GE )
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*info = -2;
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else if ( L->nrow != L->ncol || L->nrow < 0 ||
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L->Stype != SLU_SC || L->Dtype != SLU_Z || L->Mtype != SLU_TRLU )
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*info = -3;
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else if ( U->nrow != U->ncol || U->nrow < 0 ||
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U->Stype != SLU_NC || U->Dtype != SLU_Z || U->Mtype != SLU_TRU )
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*info = -4;
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else if ( ldb < SUPERLU_MAX(0, A->nrow) ||
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B->Stype != SLU_DN || B->Dtype != SLU_Z || B->Mtype != SLU_GE )
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*info = -10;
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else if ( ldx < SUPERLU_MAX(0, A->nrow) ||
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X->Stype != SLU_DN || X->Dtype != SLU_Z || X->Mtype != SLU_GE )
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*info = -11;
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if (*info != 0) {
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i = -(*info);
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xerbla_("zgsrfs", &i);
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return;
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}
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/* Quick return if possible */
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if ( A->nrow == 0 || nrhs == 0) {
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for (j = 0; j < nrhs; ++j) {
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ferr[j] = 0.;
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berr[j] = 0.;
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}
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return;
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}
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rowequ = lsame_(equed, "R") || lsame_(equed, "B");
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colequ = lsame_(equed, "C") || lsame_(equed, "B");
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/* Allocate working space */
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work = doublecomplexMalloc(2*A->nrow);
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rwork = (double *) SUPERLU_MALLOC( A->nrow * sizeof(double) );
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iwork = intMalloc(A->nrow);
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if ( !work || !rwork || !iwork )
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ABORT("Malloc fails for work/rwork/iwork.");
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if ( notran ) {
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*(unsigned char *)transc = 'N';
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transt = TRANS;
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} else {
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*(unsigned char *)transc = 'T';
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transt = NOTRANS;
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}
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/* NZ = maximum number of nonzero elements in each row of A, plus 1 */
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nz = A->ncol + 1;
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eps = dlamch_("Epsilon");
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safmin = dlamch_("Safe minimum");
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/* Set SAFE1 essentially to be the underflow threshold times the
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number of additions in each row. */
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safe1 = nz * safmin;
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safe2 = safe1 / eps;
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/* Compute the number of nonzeros in each row (or column) of A */
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for (i = 0; i < A->nrow; ++i) iwork[i] = 0;
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if ( notran ) {
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for (k = 0; k < A->ncol; ++k)
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for (i = Astore->colptr[k]; i < Astore->colptr[k+1]; ++i)
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++iwork[Astore->rowind[i]];
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} else {
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for (k = 0; k < A->ncol; ++k)
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iwork[k] = Astore->colptr[k+1] - Astore->colptr[k];
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}
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/* Copy one column of RHS B into Bjcol. */
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Bjcol.Stype = B->Stype;
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Bjcol.Dtype = B->Dtype;
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Bjcol.Mtype = B->Mtype;
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Bjcol.nrow = B->nrow;
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Bjcol.ncol = 1;
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Bjcol.Store = (void *) SUPERLU_MALLOC( sizeof(DNformat) );
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if ( !Bjcol.Store ) ABORT("SUPERLU_MALLOC fails for Bjcol.Store");
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Bjcol_store = Bjcol.Store;
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Bjcol_store->lda = ldb;
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Bjcol_store->nzval = work; /* address aliasing */
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/* Do for each right hand side ... */
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for (j = 0; j < nrhs; ++j) {
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count = 0;
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lstres = 3.;
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Bptr = &Bmat[j*ldb];
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Xptr = &Xmat[j*ldx];
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while (1) { /* Loop until stopping criterion is satisfied. */
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/* Compute residual R = B - op(A) * X,
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where op(A) = A, A**T, or A**H, depending on TRANS. */
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#ifdef _CRAY
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CCOPY(&A->nrow, Bptr, &ione, work, &ione);
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#else
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zcopy_(&A->nrow, Bptr, &ione, work, &ione);
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#endif
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sp_zgemv(transc, ndone, A, Xptr, ione, done, work, ione);
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/* Compute componentwise relative backward error from formula
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max(i) ( abs(R(i)) / ( abs(op(A))*abs(X) + abs(B) )(i) )
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where abs(Z) is the componentwise absolute value of the matrix
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or vector Z. If the i-th component of the denominator is less
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than SAFE2, then SAFE1 is added to the i-th component of the
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numerator before dividing. */
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for (i = 0; i < A->nrow; ++i) rwork[i] = z_abs1( &Bptr[i] );
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/* Compute abs(op(A))*abs(X) + abs(B). */
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if (notran) {
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for (k = 0; k < A->ncol; ++k) {
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xk = z_abs1( &Xptr[k] );
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for (i = Astore->colptr[k]; i < Astore->colptr[k+1]; ++i)
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rwork[Astore->rowind[i]] += z_abs1(&Aval[i]) * xk;
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}
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} else {
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for (k = 0; k < A->ncol; ++k) {
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s = 0.;
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for (i = Astore->colptr[k]; i < Astore->colptr[k+1]; ++i) {
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irow = Astore->rowind[i];
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s += z_abs1(&Aval[i]) * z_abs1(&Xptr[irow]);
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}
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rwork[k] += s;
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}
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}
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s = 0.;
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for (i = 0; i < A->nrow; ++i) {
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if (rwork[i] > safe2) {
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s = SUPERLU_MAX( s, z_abs1(&work[i]) / rwork[i] );
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} else if ( rwork[i] != 0.0 ) {
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s = SUPERLU_MAX( s, (z_abs1(&work[i]) + safe1) / rwork[i] );
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}
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/* If rwork[i] is exactly 0.0, then we know the true
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residual also must be exactly 0.0. */
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}
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berr[j] = s;
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/* Test stopping criterion. Continue iterating if
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1) The residual BERR(J) is larger than machine epsilon, and
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2) BERR(J) decreased by at least a factor of 2 during the
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last iteration, and
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3) At most ITMAX iterations tried. */
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if (berr[j] > eps && berr[j] * 2. <= lstres && count < ITMAX) {
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/* Update solution and try again. */
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zgstrs (trans, L, U, perm_c, perm_r, &Bjcol, stat, info);
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#ifdef _CRAY
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CAXPY(&A->nrow, &done, work, &ione,
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&Xmat[j*ldx], &ione);
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#else
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zaxpy_(&A->nrow, &done, work, &ione,
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&Xmat[j*ldx], &ione);
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#endif
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lstres = berr[j];
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++count;
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} else {
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break;
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}
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} /* end while */
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stat->RefineSteps = count;
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/* Bound error from formula:
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norm(X - XTRUE) / norm(X) .le. FERR = norm( abs(inv(op(A)))*
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( abs(R) + NZ*EPS*( abs(op(A))*abs(X)+abs(B) ))) / norm(X)
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where
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norm(Z) is the magnitude of the largest component of Z
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inv(op(A)) is the inverse of op(A)
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abs(Z) is the componentwise absolute value of the matrix or
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vector Z
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NZ is the maximum number of nonzeros in any row of A, plus 1
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EPS is machine epsilon
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The i-th component of abs(R)+NZ*EPS*(abs(op(A))*abs(X)+abs(B))
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is incremented by SAFE1 if the i-th component of
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abs(op(A))*abs(X) + abs(B) is less than SAFE2.
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Use ZLACON to estimate the infinity-norm of the matrix
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inv(op(A)) * diag(W),
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where W = abs(R) + NZ*EPS*( abs(op(A))*abs(X)+abs(B) ))) */
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for (i = 0; i < A->nrow; ++i) rwork[i] = z_abs1( &Bptr[i] );
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/* Compute abs(op(A))*abs(X) + abs(B). */
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if ( notran ) {
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for (k = 0; k < A->ncol; ++k) {
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xk = z_abs1( &Xptr[k] );
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for (i = Astore->colptr[k]; i < Astore->colptr[k+1]; ++i)
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rwork[Astore->rowind[i]] += z_abs1(&Aval[i]) * xk;
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}
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} else {
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for (k = 0; k < A->ncol; ++k) {
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s = 0.;
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for (i = Astore->colptr[k]; i < Astore->colptr[k+1]; ++i) {
|
||
|
irow = Astore->rowind[i];
|
||
|
xk = z_abs1( &Xptr[irow] );
|
||
|
s += z_abs1(&Aval[i]) * xk;
|
||
|
}
|
||
|
rwork[k] += s;
|
||
|
}
|
||
|
}
|
||
|
|
||
|
for (i = 0; i < A->nrow; ++i)
|
||
|
if (rwork[i] > safe2)
|
||
|
rwork[i] = z_abs(&work[i]) + (iwork[i]+1)*eps*rwork[i];
|
||
|
else
|
||
|
rwork[i] = z_abs(&work[i])+(iwork[i]+1)*eps*rwork[i]+safe1;
|
||
|
kase = 0;
|
||
|
|
||
|
do {
|
||
|
zlacon_(&A->nrow, &work[A->nrow], work,
|
||
|
&ferr[j], &kase);
|
||
|
if (kase == 0) break;
|
||
|
|
||
|
if (kase == 1) {
|
||
|
/* Multiply by diag(W)*inv(op(A)**T)*(diag(C) or diag(R)). */
|
||
|
if ( notran && colequ )
|
||
|
for (i = 0; i < A->ncol; ++i) {
|
||
|
zd_mult(&work[i], &work[i], C[i]);
|
||
|
}
|
||
|
else if ( !notran && rowequ )
|
||
|
for (i = 0; i < A->nrow; ++i) {
|
||
|
zd_mult(&work[i], &work[i], R[i]);
|
||
|
}
|
||
|
|
||
|
zgstrs (transt, L, U, perm_c, perm_r, &Bjcol, stat, info);
|
||
|
|
||
|
for (i = 0; i < A->nrow; ++i) {
|
||
|
zd_mult(&work[i], &work[i], rwork[i]);
|
||
|
}
|
||
|
} else {
|
||
|
/* Multiply by (diag(C) or diag(R))*inv(op(A))*diag(W). */
|
||
|
for (i = 0; i < A->nrow; ++i) {
|
||
|
zd_mult(&work[i], &work[i], rwork[i]);
|
||
|
}
|
||
|
|
||
|
zgstrs (trans, L, U, perm_c, perm_r, &Bjcol, stat, info);
|
||
|
|
||
|
if ( notran && colequ )
|
||
|
for (i = 0; i < A->ncol; ++i) {
|
||
|
zd_mult(&work[i], &work[i], C[i]);
|
||
|
}
|
||
|
else if ( !notran && rowequ )
|
||
|
for (i = 0; i < A->ncol; ++i) {
|
||
|
zd_mult(&work[i], &work[i], R[i]);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
} while ( kase != 0 );
|
||
|
|
||
|
/* Normalize error. */
|
||
|
lstres = 0.;
|
||
|
if ( notran && colequ ) {
|
||
|
for (i = 0; i < A->nrow; ++i)
|
||
|
lstres = SUPERLU_MAX( lstres, C[i] * z_abs1( &Xptr[i]) );
|
||
|
} else if ( !notran && rowequ ) {
|
||
|
for (i = 0; i < A->nrow; ++i)
|
||
|
lstres = SUPERLU_MAX( lstres, R[i] * z_abs1( &Xptr[i]) );
|
||
|
} else {
|
||
|
for (i = 0; i < A->nrow; ++i)
|
||
|
lstres = SUPERLU_MAX( lstres, z_abs1( &Xptr[i]) );
|
||
|
}
|
||
|
if ( lstres != 0. )
|
||
|
ferr[j] /= lstres;
|
||
|
|
||
|
} /* for each RHS j ... */
|
||
|
|
||
|
SUPERLU_FREE(work);
|
||
|
SUPERLU_FREE(rwork);
|
||
|
SUPERLU_FREE(iwork);
|
||
|
SUPERLU_FREE(Bjcol.Store);
|
||
|
|
||
|
return;
|
||
|
|
||
|
} /* zgsrfs */
|