dpbt02.f3

Usage

Functions/Subroutines

subroutine dpbt02 (uplo, n, kd, nrhs, a, lda, x, ldx, b, ldb, rwork, resid)
DPBT02

Function/Subroutine Documentation

subroutine dpbt02 (character uplo, integer n, integer kd, integer nrhs, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( ldx, * ) x, integer ldx, double precision, dimension( ldb, * ) b, integer ldb, double precision, dimension( * ) rwork, double precision resid)

DPBT02

Purpose:

!>
!> DPBT02 computes the residual for a solution of a symmetric banded
!> system of equations  A*x = b:
!>    RESID = norm( B - A*X ) / ( norm(A) * norm(X) * EPS)
!> where EPS is the machine precision.
!>

Parameters

UPLO

!>          UPLO is CHARACTER*1
!>          Specifies whether the upper or lower triangular part of the
!>          symmetric matrix A is stored:
!>          = 'U':  Upper triangular
!>          = 'L':  Lower triangular
!>

!>          N is INTEGER
!>          The number of rows and columns of the matrix A.  N >= 0.
!>

!>          KD is INTEGER
!>          The number of super-diagonals of the matrix A if UPLO = 'U',
!>          or the number of sub-diagonals if UPLO = 'L'.  KD >= 0.
!>

NRHS

!>          NRHS is INTEGER
!>          The number of right hand sides. NRHS >= 0.
!>

!>          A is DOUBLE PRECISION array, dimension (LDA,N)
!>          The original symmetric band matrix A.  If UPLO = 'U', the
!>          upper triangular part of A is stored as a band matrix; if
!>          UPLO = 'L', the lower triangular part of A is stored.  The
!>          columns of the appropriate triangle are stored in the columns
!>          of A and the diagonals of the triangle are stored in the rows
!>          of A.  See DPBTRF for further details.
!>

LDA

!>          LDA is INTEGER.
!>          The leading dimension of the array A.  LDA >= max(1,KD+1).
!>

!>          X is DOUBLE PRECISION array, dimension (LDX,NRHS)
!>          The computed solution vectors for the system of linear
!>          equations.
!>

LDX

!>          LDX is INTEGER
!>          The leading dimension of the array X.   LDX >= max(1,N).
!>

!>          B is DOUBLE PRECISION array, dimension (LDB,NRHS)
!>          On entry, the right hand side vectors for the system of
!>          linear equations.
!>          On exit, B is overwritten with the difference B - A*X.
!>

LDB

!>          LDB is INTEGER
!>          The leading dimension of the array B.  LDB >= max(1,N).
!>

RWORK

!>          RWORK is DOUBLE PRECISION array, dimension (N)
!>

RESID

!>          RESID is DOUBLE PRECISION
!>          The maximum over the number of right hand sides of
!>          norm(B - A*X) / ( norm(A) * norm(X) * EPS ).
!>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 134 of file dpbt02.f.