👤
Home Man
Search
Today's Posts
Register

Linux & Unix Commands - Search Man Pages
Man Page or Keyword Search:
Select Section of Man Page:
Select Man Page Repository:

RedHat 9 (Linux i386) - man page for dgbtf2 (redhat section l)

DGBTF2(l)					)					DGBTF2(l)

NAME
       DGBTF2 - compute an LU factorization of a real m-by-n band matrix A using partial pivoting
       with row interchanges

SYNOPSIS
       SUBROUTINE DGBTF2( M, N, KL, KU, AB, LDAB, IPIV, INFO )

	   INTEGER	  INFO, KL, KU, LDAB, M, N

	   INTEGER	  IPIV( * )

	   DOUBLE	  PRECISION AB( LDAB, * )

PURPOSE
       DGBTF2 computes an LU factorization of a real m-by-n band matrix A using partial  pivoting
       with  row  interchanges.   This is the unblocked version of the algorithm, calling Level 2
       BLAS.

ARGUMENTS
       M       (input) INTEGER
	       The number of rows of the matrix A.  M >= 0.

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

       KL      (input) INTEGER
	       The number of subdiagonals within the band of A.  KL >= 0.

       KU      (input) INTEGER
	       The number of superdiagonals within the band of A.  KU >= 0.

       AB      (input/output) DOUBLE PRECISION array, dimension (LDAB,N)
	       On entry, the matrix A in band storage, in rows KL+1 to 2*KL+KU+1; rows 1 to KL of
	       the  array  need not be set.  The j-th column of A is stored in the j-th column of
	       the   array   AB   as   follows:   AB(kl+ku+1+i-j,j)   =   A(i,j)   for	 max(1,j-
	       ku)<=i<=min(m,j+kl)

	       On  exit,  details  of  the factorization: U is stored as an upper triangular band
	       matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, and  the	multipliers  used
	       during  the  factorization are stored in rows KL+KU+2 to 2*KL+KU+1.  See below for
	       further details.

       LDAB    (input) INTEGER
	       The leading dimension of the array AB.  LDAB >= 2*KL+KU+1.

       IPIV    (output) INTEGER array, dimension (min(M,N))
	       The pivot indices; for 1 <= i <= min(M,N), row i of the	matrix	was  interchanged
	       with row IPIV(i).

       INFO    (output) INTEGER
	       = 0: successful exit
	       < 0: if INFO = -i, the i-th argument had an illegal value
	       >  0:  if INFO = +i, U(i,i) is exactly zero. The factorization has been completed,
	       but the factor U is exactly singular, and division by zero will	occur  if  it  is
	       used to solve a system of equations.

FURTHER DETAILS
       The  band  storage scheme is illustrated by the following example, when M = N = 6, KL = 2,
       KU = 1:

       On entry:		       On exit:

	   *	*    *	  +    +    +	    *	 *    *   u14  u25  u36
	   *	*    +	  +    +    +	    *	 *   u13  u24  u35  u46
	   *   a12  a23  a34  a45  a56	    *	u12  u23  u34  u45  u56
	  a11  a22  a33  a44  a55  a66	   u11	u22  u33  u44  u55  u66
	  a21  a32  a43  a54  a65   *	   m21	m32  m43  m54  m65   *
	  a31  a42  a53  a64   *    *	   m31	m42  m53  m64	*    *

       Array elements marked * are not used by the routine; elements marked + need not be set  on
       entry,  but are required by the routine to store elements of U, because of fill-in result-
       ing from the row
       interchanges.

LAPACK version 3.0			   15 June 2000 				DGBTF2(l)


All times are GMT -4. The time now is 08:14 PM.

Unix & Linux Forums Content Copyrightę1993-2018. All Rights Reserved.
×
UNIX.COM Login
Username:
Password:  
Show Password