sgsequ_dist.c File Reference

Computes row and column scalings. More...

#include <math.h>
#include "superlu_sdefs.h"

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Functions
void	sgsequ_dist (SuperMatrix *A, float *r, float *c, float *rowcnd, float *colcnd, float *amax, int *info)

Detailed Description

Computes row and column scalings.

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.

-- SuperLU routine (version 2.0) --
Univ. of California Berkeley, Xerox Palo Alto Research Center,
and Lawrence Berkeley National Lab.
November 15, 1997

Modified from LAPACK routine SGEEQU

Function Documentation

sgsequ_dist()

void sgsequ_dist	(	SuperMatrix *	A,
		float *	r,
		float *	c,
		float *	rowcnd,
		float *	colcnd,
		float *	amax,
		int *	info
	)

Purpose
  =======

  SGSEQU_DIST computes row and column scalings intended to equilibrate an
  M-by-N sparse matrix A and reduce its condition number. R returns the row
  scale factors and C the column scale factors, chosen to try to make
  the largest element in each row and column of the matrix B with
  elements B(i,j)=R(i)*A(i,j)*C(j) have absolute value 1.

  R(i) and C(j) are restricted to be between SMLNUM = smallest safe
  number and BIGNUM = largest safe number.  Use of these scaling
  factors is not guaranteed to reduce the condition number of A but
  works well in practice.

  See supermatrix.h for the definition of 'SuperMatrix' structure.

  Arguments
  =========

  A       (input) SuperMatrix*
          The matrix of dimension (A->nrow, A->ncol) whose equilibration
          factors are to be computed. The type of A can be:
          Stype = SLU_NC; Dtype = SLU_S; Mtype = SLU_GE.

  R       (output) float*, size A->nrow
          If INFO = 0 or INFO > M, R contains the row scale factors
          for A.

  C       (output) float*, size A->ncol
          If INFO = 0,  C contains the column scale factors for A.

  ROWCND  (output) float*
          If INFO = 0 or INFO > M, ROWCND contains the ratio of the
          smallest R(i) to the largest R(i).  If ROWCND >= 0.1 and
          AMAX is neither too large nor too small, it is not worth
          scaling by R.

  COLCND  (output) float*
          If INFO = 0, COLCND contains the ratio of the smallest
          C(i) to the largest C(i).  If COLCND >= 0.1, it is not
          worth scaling by C.

  AMAX    (output) float*
          Absolute value of largest matrix element.  If AMAX is very
          close to overflow or very close to underflow, the matrix
          should be scaled.

  INFO    (output) int*
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument had an illegal value
          > 0:  if INFO = i,  and i is
                <= A->nrow:  the i-th row of A is exactly zero
                >  A->ncol:  the (i-M)-th column of A is exactly zero

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

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