# SRC/dgscon.c File Reference

Estimates reciprocal of the condition number of a general matrix. More...

`#include <math.h>`
`#include "slu_ddefs.h"`

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

## Detailed Description

     -- SuperLU routine (version 3.0) --
     Univ. of California Berkeley, Xerox Palo Alto Research Center,
     and Lawrence Berkeley National Lab.
     October 15, 2003

     Modified from lapack routines DGECON.

## Function Documentation

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

       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

        =====================================================================