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## man page of LAPACK-3

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

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## NAME

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

DOUBLE PRECISION FUNCTION ZLA_PORPVGRW( UPLO, NCOLS, A, LDA, AF, LDAF, WORK ) IMPLICIT NONE CHARACTER*1 UPLO INTEGER NCOLS, LDA, LDAF COMPLEX*16 A( LDA, * ), AF( LDAF, * ) DOUBLE PRECISION WORK( * )## PURPOSE

ZLA_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) COMPLEX*16 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) COMPLEX*16 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 ZPOTRF. LDAF (input) INTEGER The leading dimension of the array AF. LDAF >= max(1,N). WORK (input) COMPLEX*16 array, dimension (2*N) LAPACK routine (version 3.2.2)March 2011 LAPACK-3(3)

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