# sla_syrpvgrw.f man page

sla_syrpvgrw.f

## Synopsis

### Functions/Subroutines

real function **sla_syrpvgrw** (UPLO, **N**, INFO, A, **LDA**, AF, LDAF, IPIV, WORK)**SLA_SYRPVGRW** computes the reciprocal pivot growth factor norm(A)/norm(U) for a symmetric indefinite matrix.

## Function/Subroutine Documentation

### real function sla_syrpvgrw (character*1 UPLO, integer N, integer INFO, real, dimension( lda, * ) A, integer LDA, real, dimension( ldaf, * ) AF, integer LDAF, integer, dimension( * ) IPIV, real, dimension( * ) WORK)

**SLA_SYRPVGRW** computes the reciprocal pivot growth factor norm(A)/norm(U) for a symmetric indefinite matrix.

**Purpose:**

SLA_SYRPVGRW computes the reciprocal pivot growth factor norm(A)/norm(U). The "max absolute element" norm is used. If this is much less than 1, the stability of the LU factorization of the (equilibrated) matrix A could be poor. This also means that the solution X, estimated condition numbers, and error bounds could be unreliable.

**Parameters:**-
*UPLO*UPLO is CHARACTER*1 = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored.

*N*N is INTEGER The number of linear equations, i.e., the order of the matrix A. N >= 0.

*INFO*INFO is INTEGER The value of INFO returned from SSYTRF, .i.e., the pivot in column INFO is exactly 0.

*A*A is REAL array, dimension (LDA,N) On entry, the N-by-N matrix A.

*LDA*LDA is INTEGER The leading dimension of the array A. LDA >= max(1,N).

*AF*AF is REAL array, dimension (LDAF,N) The block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by SSYTRF.

*LDAF*LDAF is INTEGER The leading dimension of the array AF. LDAF >= max(1,N).

*IPIV*IPIV is INTEGER array, dimension (N) Details of the interchanges and the block structure of D as determined by SSYTRF.

*WORK*WORK is REAL array, dimension (2*N)

**Author:**-
Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**December 2016

Definition at line 124 of file sla_syrpvgrw.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page sla_syrpvgrw(3) is an alias of sla_syrpvgrw.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK