DPBRFS man page on IRIX

Man page or keyword search:  
man Server   31559 pages
apropos Keyword Search (all sections)
Output format
IRIX logo
[printable version]



DPBRFS(3F)							    DPBRFS(3F)

NAME
     DPBRFS - improve the computed solution to a system of linear equations
     when the coefficient matrix is symmetric positive definite and banded,
     and provides error bounds and backward error estimates for the solution

SYNOPSIS
     SUBROUTINE DPBRFS( UPLO, N, KD, NRHS, AB, LDAB, AFB, LDAFB, B, LDB, X,
			LDX, FERR, BERR, WORK, IWORK, INFO )

	 CHARACTER	UPLO

	 INTEGER	INFO, KD, LDAB, LDAFB, LDB, LDX, N, NRHS

	 INTEGER	IWORK( * )

	 DOUBLE		PRECISION AB( LDAB, * ), AFB( LDAFB, * ), B( LDB, * ),
			BERR( * ), FERR( * ), WORK( * ), X( LDX, * )

PURPOSE
     DPBRFS improves the computed solution to a system of linear equations
     when the coefficient matrix is symmetric positive definite and banded,
     and provides error bounds and backward error estimates for the solution.

ARGUMENTS
     UPLO    (input) CHARACTER*1
	     = 'U':  Upper triangle of A is stored;
	     = 'L':  Lower triangle of A is stored.

     N	     (input) INTEGER
	     The order of the matrix A.	 N >= 0.

     KD	     (input) INTEGER
	     The number of superdiagonals of the matrix A if UPLO = 'U', or
	     the number of subdiagonals if UPLO = 'L'.	KD >= 0.

     NRHS    (input) INTEGER
	     The number of right hand sides, i.e., the number of columns of
	     the matrices B and X.  NRHS >= 0.

     AB	     (input) DOUBLE PRECISION array, dimension (LDAB,N)
	     The upper or lower triangle of the symmetric band matrix A,
	     stored in the first KD+1 rows of the array.  The j-th column of A
	     is stored in the j-th column of the array AB as follows:  if UPLO
	     = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j; if UPLO =
	     'L', AB(1+i-j,j)	 = A(i,j) for j<=i<=min(n,j+kd).

     LDAB    (input) INTEGER
	     The leading dimension of the array AB.  LDAB >= KD+1.

									Page 1

DPBRFS(3F)							    DPBRFS(3F)

     AFB     (input) DOUBLE PRECISION array, dimension (LDAFB,N)
	     The triangular factor U or L from the Cholesky factorization A =
	     U**T*U or A = L*L**T of the band matrix A as computed by DPBTRF,
	     in the same storage format as A (see AB).

     LDAFB   (input) INTEGER
	     The leading dimension of the array AFB.  LDAFB >= KD+1.

     B	     (input) DOUBLE PRECISION array, dimension (LDB,NRHS)
	     The right hand side matrix B.

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

     X	     (input/output) DOUBLE PRECISION array, dimension (LDX,NRHS)
	     On entry, the solution matrix X, as computed by DPBTRS.  On exit,
	     the improved solution matrix X.

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

     FERR    (output) DOUBLE PRECISION array, dimension (NRHS)
	     The estimated forward error bound for each solution vector X(j)
	     (the j-th 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).  The
	     estimate is as reliable as the estimate for RCOND, and is almost
	     always a slight overestimate of the true error.

     BERR    (output) 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).

     WORK    (workspace) DOUBLE PRECISION array, dimension (3*N)

     IWORK   (workspace) INTEGER array, dimension (N)

     INFO    (output) INTEGER
	     = 0:  successful exit
	     < 0:  if INFO = -i, the i-th argument had an illegal value

PARAMETERS
     ITMAX is the maximum number of steps of iterative refinement.

									Page 2

[top]

List of man pages available for IRIX

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net