/*! \file
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
at the top-level directory.
*/

/*! @file dgscon.c
 * \brief Estimates reciprocal of the condition number of a general matrix
 * 
 * <pre>
 * -- SuperLU routine (version 5.0) --
 * Univ. of California Berkeley, Xerox Palo Alto Research Center,
 * and Lawrence Berkeley National Lab.
 * July 25, 2015
 *
 * Modified from lapack routines DGECON.
 * </pre> 
 */

/*
 * File name:	dgscon.c
 * History:     Modified from lapack routines DGECON.
 */
#include <math.h>
#include "slu_ddefs.h"

/*! \brief
 *
 * <pre>
 *   Purpose   
 *   =======   
 *
 *   DGSCON estimates the reciprocal of the condition number of a general 
 *   real matrix A, in either the 1-norm or the infinity-norm, using   
 *   the LU factorization computed by DGETRF.   *
 *
 *   An estimate is obtained for norm(inv(A)), and the reciprocal of the   
 *   condition number is computed as   
 *      RCOND = 1 / ( norm(A) * norm(inv(A)) ).   
 *
 *   See supermatrix.h for the definition of 'SuperMatrix' structure.
 * 
 *   Arguments   
 *   =========   
 *
 *    NORM    (input) char*
 *            Specifies whether the 1-norm condition number or the   
 *            infinity-norm condition number is required:   
 *            = '1' or 'O':  1-norm;   
 *            = 'I':         Infinity-norm.
 *	    
 *    L       (input) SuperMatrix*
 *            The factor L from the factorization Pr*A*Pc=L*U as computed by
 *            dgstrf(). Use compressed row subscripts storage for supernodes,
 *            i.e., L has types: Stype = SLU_SC, Dtype = SLU_D, Mtype = SLU_TRLU.
 * 
 *    U       (input) SuperMatrix*
 *            The factor U from the factorization Pr*A*Pc=L*U as computed by
 *            dgstrf(). Use column-wise storage scheme, i.e., U has types:
 *            Stype = SLU_NC, Dtype = SLU_D, Mtype = SLU_TRU.
 *	    
 *    ANORM   (input) double
 *            If NORM = '1' or 'O', the 1-norm of the original matrix A.   
 *            If NORM = 'I', the infinity-norm of the original matrix A.
 *	    
 *    RCOND   (output) double*
 *           The reciprocal of the condition number of the matrix A,   
 *           computed as RCOND = 1/(norm(A) * norm(inv(A))).
 *	    
 *    INFO    (output) int*
 *           = 0:  successful exit   
 *           < 0:  if INFO = -i, the i-th argument had an illegal value   
 *
 *    ===================================================================== 
 * </pre>
 */

void
dgscon(char *norm, SuperMatrix *L, SuperMatrix *U,
       double anorm, double *rcond, SuperLUStat_t *stat, int *info)
{


    /* Local variables */
    int    kase, kase1, onenrm, i;
    double ainvnm;
    double *work;
    int    *iwork;
    int    isave[3];
    extern int drscl_(int *, double *, double *, int *);

    extern int dlacon2_(int *, double *, double *, int *, double *, int *, int []);

    
    /* Test the input parameters. */
    *info = 0;
    onenrm = *(unsigned char *)norm == '1' || strncmp(norm, "O", 1)==0;
    if (! onenrm && ! strncmp(norm, "I", 1)==0) *info = -1;
    else if (L->nrow < 0 || L->nrow != L->ncol ||
             L->Stype != SLU_SC || L->Dtype != SLU_D || L->Mtype != SLU_TRLU)
	 *info = -2;
    else if (U->nrow < 0 || U->nrow != U->ncol ||
             U->Stype != SLU_NC || U->Dtype != SLU_D || U->Mtype != SLU_TRU) 
	*info = -3;
    if (*info != 0) {
	i = -(*info);
	input_error("dgscon", &i);
	return;
    }

    /* Quick return if possible */
    *rcond = 0.;
    if ( L->nrow == 0 || U->nrow == 0) {
	*rcond = 1.;
	return;
    }

    work = doubleCalloc( 3*L->nrow );
    iwork = intMalloc( L->nrow );


    if ( !work || !iwork )
	ABORT("Malloc fails for work arrays in dgscon.");
    
    /* Estimate the norm of inv(A). */
    ainvnm = 0.;
    if ( onenrm ) kase1 = 1;
    else kase1 = 2;
    kase = 0;

    do {
	dlacon2_(&L->nrow, &work[L->nrow], &work[0], &iwork[0], &ainvnm, &kase, isave);

	if (kase == 0) break;

	if (kase == kase1) {
	    /* Multiply by inv(L). */
	    sp_dtrsv("L", "No trans", "Unit", L, U, &work[0], stat, info);

	    /* Multiply by inv(U). */
	    sp_dtrsv("U", "No trans", "Non-unit", L, U, &work[0], stat, info);
	    
	} else {

	    /* Multiply by inv(U'). */
	    sp_dtrsv("U", "Transpose", "Non-unit", L, U, &work[0], stat, info);

	    /* Multiply by inv(L'). */
	    sp_dtrsv("L", "Transpose", "Unit", L, U, &work[0], stat, info);
	    
	}

    } while ( kase != 0 );

    /* Compute the estimate of the reciprocal condition number. */
    if (ainvnm != 0.) *rcond = (1. / ainvnm) / anorm;

    SUPERLU_FREE (work);
    SUPERLU_FREE (iwork);
    return;

} /* dgscon */

