cptrfs man page on IRIX

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



CPTRFS(3F)							    CPTRFS(3F)

NAME
     CPTRFS - improve 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

SYNOPSIS
     SUBROUTINE CPTRFS( UPLO, N, NRHS, D, E, DF, EF, B, LDB, X, LDX, FERR,
			BERR, WORK, RWORK, INFO )

	 CHARACTER	UPLO

	 INTEGER	INFO, LDB, LDX, N, NRHS

	 REAL		BERR( * ), D( * ), DF( * ), FERR( * ), RWORK( * )

	 COMPLEX	B( LDB, * ), E( * ), EF( * ), WORK( * ), X( LDX, * )

PURPOSE
     CPTRFS 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.

ARGUMENTS
     UPLO    (input) 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.)

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

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

     D	     (input) REAL array, dimension (N)
	     The n real diagonal elements of the tridiagonal matrix A.

     E	     (input) COMPLEX array, dimension (N-1)
	     The (n-1) off-diagonal elements of the tridiagonal matrix A (see
	     UPLO).

     DF	     (input) REAL array, dimension (N)
	     The n diagonal elements of the diagonal matrix D from the
	     factorization computed by CPTTRF.

									Page 1

CPTRFS(3F)							    CPTRFS(3F)

     EF	     (input) COMPLEX array, dimension (N-1)
	     The (n-1) off-diagonal elements of the unit bidiagonal factor U
	     or L from the factorization computed by CPTTRF (see UPLO).

     B	     (input) COMPLEX 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) COMPLEX array, dimension (LDX,NRHS)
	     On entry, the solution matrix X, as computed by CPTTRS.  On exit,
	     the improved solution matrix X.

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

     FERR    (output) REAL array, dimension (NRHS)
	     The 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).

     BERR    (output) REAL 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) COMPLEX array, dimension (N)

     RWORK   (workspace) REAL 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