zptrfs.f (3)  Linux Manuals
NAME
zptrfs.f 
SYNOPSIS
Functions/Subroutines
subroutine zptrfs (UPLO, N, NRHS, D, E, DF, EF, B, LDB, X, LDX, FERR, BERR, WORK, RWORK, INFO)
ZPTRFS
Function/Subroutine Documentation
subroutine zptrfs (characterUPLO, integerN, integerNRHS, double precision, dimension( * )D, complex*16, dimension( * )E, double precision, dimension( * )DF, complex*16, dimension( * )EF, complex*16, dimension( ldb, * )B, integerLDB, complex*16, dimension( ldx, * )X, integerLDX, double precision, dimension( * )FERR, double precision, dimension( * )BERR, complex*16, dimension( * )WORK, double precision, dimension( * )RWORK, integerINFO)
ZPTRFS
Purpose:

ZPTRFS improves the computed solution to a system of linear equations when the coefficient matrix is Hermitian positive definite and tridiagonal, and provides error bounds and backward error estimates for the solution.
Parameters:

UPLO
UPLO is CHARACTER*1 Specifies whether the superdiagonal or the subdiagonal of the tridiagonal matrix A is stored and the form of the factorization: = 'U': E is the superdiagonal of A, and A = U**H*D*U; = 'L': E is the subdiagonal of A, and A = L*D*L**H. (The two forms are equivalent if A is real.)
NN is INTEGER The order of the matrix A. N >= 0.
NRHSNRHS is INTEGER The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0.
DD is DOUBLE PRECISION array, dimension (N) The n real diagonal elements of the tridiagonal matrix A.
EE is COMPLEX*16 array, dimension (N1) The (n1) offdiagonal elements of the tridiagonal matrix A (see UPLO).
DFDF is DOUBLE PRECISION array, dimension (N) The n diagonal elements of the diagonal matrix D from the factorization computed by ZPTTRF.
EFEF is COMPLEX*16 array, dimension (N1) The (n1) offdiagonal elements of the unit bidiagonal factor U or L from the factorization computed by ZPTTRF (see UPLO).
BB is COMPLEX*16 array, dimension (LDB,NRHS) The right hand side matrix B.
LDBLDB is INTEGER The leading dimension of the array B. LDB >= max(1,N).
XX is COMPLEX*16 array, dimension (LDX,NRHS) On entry, the solution matrix X, as computed by ZPTTRS. On exit, the improved solution matrix X.
LDXLDX is INTEGER The leading dimension of the array X. LDX >= max(1,N).
FERRFERR is DOUBLE PRECISION array, dimension (NRHS) The forward error bound for each solution vector X(j) (the jth column of the solution matrix X). If XTRUE is the true solution corresponding to X(j), FERR(j) is an estimated upper bound for the magnitude of the largest element in (X(j)  XTRUE) divided by the magnitude of the largest element in X(j).
BERRBERR is DOUBLE PRECISION array, dimension (NRHS) The componentwise relative backward error of each solution vector X(j) (i.e., the smallest relative change in any element of A or B that makes X(j) an exact solution).
WORKWORK is COMPLEX*16 array, dimension (N)
RWORKRWORK is DOUBLE PRECISION array, dimension (N)
INFOINFO is INTEGER = 0: successful exit < 0: if INFO = i, the ith argument had an illegal value
Internal Parameters:

ITMAX is the maximum number of steps of iterative refinement.
Author:

Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
 September 2012
Definition at line 183 of file zptrfs.f.
Author
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