# sla_porpvgrw.f - Man Page

SRC/sla_porpvgrw.f

## Synopsis

### Functions/Subroutines

real function **sla_porpvgrw** (uplo, ncols, a, lda, af, ldaf, work)**SLA_PORPVGRW** computes the reciprocal pivot growth factor norm(A)/norm(U) for a symmetric or Hermitian positive-definite matrix.

## Function/Subroutine Documentation

### real function sla_porpvgrw (character*1 uplo, integer ncols, real, dimension( lda, * ) a, integer lda, real, dimension( ldaf, * ) af, integer ldaf, real, dimension( * ) work)

**SLA_PORPVGRW** computes the reciprocal pivot growth factor norm(A)/norm(U) for a symmetric or Hermitian positive-definite matrix.

**Purpose:**

SLA_PORPVGRW 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.

*NCOLS*NCOLS is INTEGER The number of columns of the matrix A. NCOLS >= 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 triangular factor U or L from the Cholesky factorization A = U**T*U or A = L*L**T, as computed by SPOTRF.

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

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

**Author**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **103** of file **sla_porpvgrw.f**.

## Author

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## Referenced By

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

Tue Nov 28 2023 12:08:42 Version 3.12.0 LAPACK