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<meta content="text/html;charset=UTF-8" http-equiv="Content-Type">
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<title>SuperLU: SRC/dgsequ.c File Reference</title>
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Main Page
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Data Structures
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Files
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SRC/dgsequ.c File ReferenceComputes row and column scalings. More...
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#include <math.h>
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#include "slu_ddefs.h"
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Functions
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void dgsequ (SuperMatrix *A, double *r, double *c, double *rowcnd, double *colcnd, double *amax, int *info)
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Driver related.
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Detailed Description
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-- SuperLU routine (version 2.0) --
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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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November 15, 1997
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Modified from LAPACK routine DGEEQU
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Function Documentation
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void dgsequ
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(
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SuperMatrix *
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A,
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double *
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r,
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double *
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c,
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double *
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rowcnd,
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double *
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colcnd,
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double *
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amax,
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int *
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info
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)
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Purpose
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=======
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DGSEQU computes row and column scalings intended to equilibrate an
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M-by-N sparse matrix A and reduce its condition number. R returns the row
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scale factors and C the column scale factors, chosen to try to make
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the largest element in each row and column of the matrix B with
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elements B(i,j)=R(i)*A(i,j)*C(j) have absolute value 1.
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R(i) and C(j) are restricted to be between SMLNUM = smallest safe
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number and BIGNUM = largest safe number. Use of these scaling
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factors is not guaranteed to reduce the condition number of A but
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works well in practice.
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See supermatrix.h for the definition of 'SuperMatrix' structure.
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Arguments
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=========
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A (input) SuperMatrix*
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The matrix of dimension (A->nrow, A->ncol) whose equilibration
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factors are to be computed. The type of A can be:
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Stype = SLU_NC; Dtype = SLU_D; Mtype = SLU_GE.
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R (output) double*, size A->nrow
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If INFO = 0 or INFO > M, R contains the row scale factors
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for A.
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C (output) double*, size A->ncol
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If INFO = 0, C contains the column scale factors for A.
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ROWCND (output) double*
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If INFO = 0 or INFO > M, ROWCND contains the ratio of the
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smallest R(i) to the largest R(i). If ROWCND >= 0.1 and
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AMAX is neither too large nor too small, it is not worth
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scaling by R.
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COLCND (output) double*
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If INFO = 0, COLCND contains the ratio of the smallest
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C(i) to the largest C(i). If COLCND >= 0.1, it is not
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worth scaling by C.
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AMAX (output) double*
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Absolute value of largest matrix element. If AMAX is very
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close to overflow or very close to underflow, the matrix
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should be scaled.
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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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> 0: if INFO = i, and i is
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<= A->nrow: the i-th row of A is exactly zero
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> A->ncol: the (i-M)-th column of A is exactly zero
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=====================================================================
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<address style="text-align: right;"><small>Generated on Mon Nov 22 10:23:47 2010 for SuperLU by </small></address>
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 1.5.5
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