NAMELAPACK-3 - computes the reciprocal pivot growth factor norm(A)/norm(U)
SYNOPSISDOUBLE PRECISION FUNCTION ZLA_SYRPVGRW( UPLO, N, INFO, A, LDA, AF, LDAF, IPIV, WORK ) IMPLICIT NONE CHARACTER*1 UPLO INTEGER N, INFO, LDA, LDAF COMPLEX*16 A( LDA, * ), AF( LDAF, * ) DOUBLE PRECISION WORK( * ) INTEGER IPIV( * )
PURPOSEZLA_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.
ARGUMENTSUPLO (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 ZSYTRF, .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) 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 block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by ZSYTRF. 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 ZSYTRF. WORK (input) COMPLEX*16 array, dimension (2*N) LAPACK routine (version 3.2.2)March 2011 LAPACK-3(3)