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CentOS 7.0 - man page for dgbsv (centos section 3)

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dgbsv.f(3)				      LAPACK				       dgbsv.f(3)

NAME
       dgbsv.f -

SYNOPSIS
   Functions/Subroutines
       subroutine dgbsv (N, KL, KU, NRHS, AB, LDAB, IPIV, B, LDB, INFO)
	    DGBSV computes the solution to system of linear equations A * X = B for GB matrices
	   (simple driver)

Function/Subroutine Documentation
   subroutine dgbsv (integerN, integerKL, integerKU, integerNRHS, double precision, dimension(
       ldab, * )AB, integerLDAB, integer, dimension( * )IPIV, double precision, dimension( ldb, *
       )B, integerLDB, integerINFO)
	DGBSV computes the solution to system of linear equations A * X = B for GB matrices
       (simple driver)

       Purpose:

	    DGBSV computes the solution to a real system of linear equations
	    A * X = B, where A is a band matrix of order N with KL subdiagonals
	    and KU superdiagonals, and X and B are N-by-NRHS matrices.

	    The LU decomposition with partial pivoting and row interchanges is
	    used to factor A as A = L * U, where L is a product of permutation
	    and unit lower triangular matrices with KL subdiagonals, and U is
	    upper triangular with KL+KU superdiagonals.  The factored form of A
	    is then used to solve the system of equations A * X = B.

       Parameters:
	   N

		     N is INTEGER
		     The number of linear equations, i.e., the order of the
		     matrix A.	N >= 0.

	   KL

		     KL is INTEGER
		     The number of subdiagonals within the band of A.  KL >= 0.

	   KU

		     KU is INTEGER
		     The number of superdiagonals within the band of A.  KU >= 0.

	   NRHS

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

	   AB

		     AB is 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(N,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

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

	   IPIV

		     IPIV is INTEGER array, dimension (N)
		     The pivot indices that define the permutation matrix P;
		     row i of the matrix was interchanged with row IPIV(i).

	   B

		     B is DOUBLE PRECISION array, dimension (LDB,NRHS)
		     On entry, the N-by-NRHS right hand side matrix B.
		     On exit, if INFO = 0, the N-by-NRHS solution matrix X.

	   LDB

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

	   INFO

		     INFO is 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 the solution has not been computed.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   November 2011

       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 resulting from the row interchanges.

       Definition at line 163 of file dgbsv.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2				 Tue Sep 25 2012			       dgbsv.f(3)


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