Provided by: liblapack-doc_3.3.1-1_all

**NAME**

LAPACK-3 - computes the reciprocal pivot growth factor norm(A)/norm(U)

**SYNOPSIS**

REAL FUNCTION SLA_PORPVGRW( UPLO, NCOLS, A, LDA, AF, LDAF, WORK ) IMPLICIT NONE CHARACTER*1 UPLO INTEGER NCOLS, LDA, LDAF REAL A( LDA, * ), AF( LDAF, * ), WORK( * )

**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.

**ARGUMENTS**

UPLO (input) CHARACTER*1 = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored. NCOLS (input) INTEGER The number of columns of the matrix A. NCOLS >= 0. A (input) REAL array, dimension (LDA,N) On entry, the N-by-N matrix A. LDA (input) INTEGER The leading dimension of the array A. LDA >= max(1,N). AF (input) 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 (input) INTEGER The leading dimension of the array AF. LDAF >= max(1,N). WORK (input) REAL array, dimension (2*N) LAPACK routine (version 3.2.2) April 2011 SLA_PORPVGRW(3lapack)