Provided by: liblapack-doc_3.3.1-1_all

**NAME**

LAPACK-3 - DLA_PORCOND Estimate the Skeel condition number of op(A) * op2(C) where op2 is determined by CMODE as follows CMODE = 1 op2(C) = C CMODE = 0 op2(C) = I CMODE = -1 op2(C) = inv(C) The Skeel condition number cond(A) = norminf( |inv(A)||A| ) is computed by computing scaling factors R such that diag(R)*A*op2(C) is row equilibrated and computing the standard infinity-norm condition number

**SYNOPSIS**

DOUBLE PRECISION FUNCTION DLA_PORCOND( UPLO, N, A, LDA, AF, LDAF, CMODE, C, INFO, WORK, IWORK ) IMPLICIT NONE CHARACTER UPLO INTEGER N, LDA, LDAF, INFO, CMODE DOUBLE PRECISION A( LDA, * ), AF( LDAF, * ), WORK( * ), C( * ) INTEGER IWORK( * )

**PURPOSE**

DLA_PORCOND Estimates the Skeel condition number of op(A) * op2(C) where op2 is determined by CMODE as follows CMODE = 1 op2(C) = C CMODE = 0 op2(C) = I CMODE = -1 op2(C) = inv(C) The Skeel condition number cond(A) = norminf( |inv(A)||A| ) is computed by computing scaling factors R such that diag(R)*A*op2(C) is row equilibrated and computing the standard infinity-norm condition number.

**ARGUMENTS**

UPLO (input) CHARACTER*1 = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored. N (input) INTEGER The number of linear equations, i.e., the order of the matrix A. N >= 0. A (input) DOUBLE PRECISION 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) DOUBLE PRECISION 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 DPOTRF. LDAF (input) INTEGER The leading dimension of the array AF. LDAF >= max(1,N). CMODE (input) INTEGER Determines op2(C) in the formula op(A) * op2(C) as follows: CMODE = 1 op2(C) = C CMODE = 0 op2(C) = I CMODE = -1 op2(C) = inv(C) C (input) DOUBLE PRECISION array, dimension (N) The vector C in the formula op(A) * op2(C). INFO (output) INTEGER = 0: Successful exit. i > 0: The ith argument is invalid. WORK (input) DOUBLE PRECISION array, dimension (3*N). Workspace. IWORK (input) INTEGER array, dimension (N). Workspace. LAPACK routine (version 3.2.2) April 2011 DLA_PORCOND(3lapack)