Provided by: liblapack-doc_3.3.1-1_all
LAPACK-3 - computes the reciprocal pivot growth factor norm(A)/norm(U)
REAL FUNCTION SLA_SYRPVGRW( UPLO, N, INFO, A, LDA, AF, LDAF, IPIV, WORK ) IMPLICIT NONE CHARACTER*1 UPLO INTEGER N, INFO, LDA, LDAF INTEGER IPIV( * ) REAL A( LDA, * ), AF( LDAF, * ), WORK( * )
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.
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. INFO (input) INTEGER The value of INFO returned from SSYTRF, .i.e., the pivot in column INFO is exactly 0. 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 block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by SSYTRF. LDAF (input) INTEGER The leading dimension of the array AF. LDAF >= max(1,N). IPIV (input) INTEGER array, dimension (N) Details of the interchanges and the block structure of D as determined by SSYTRF. WORK (input) REAL array, dimension (2*N) LAPACK routine (version 3.2.2) April 2011 SLA_SYRPVGRW(3lapack)