dgesv(l) [redhat man page]

DGESV(l)								 )								  DGESV(l)

NAME

       DGESV - compute the solution to a real system of linear equations A * X = B,

SYNOPSIS

       SUBROUTINE DGESV( N, NRHS, A, LDA, IPIV, B, LDB, INFO )

	   INTEGER	 INFO, LDA, LDB, N, NRHS

	   INTEGER	 IPIV( * )

	   DOUBLE	 PRECISION A( LDA, * ), B( LDB, * )

PURPOSE

       DGESV computes the solution to a real system of linear equations A * X = B, where A is an N-by-N matrix 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 = P * L * U,
       where  P  is a permutation matrix, L is unit lower triangular, and U is upper triangular.  The factored form of A is then used to solve the
       system of equations A * X = B.

ARGUMENTS

       N       (input) INTEGER
	       The number of linear equations, i.e., 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.

       A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
	       On entry, the N-by-N coefficient matrix A.  On exit, the factors L and U from the factorization A = P*L*U; the unit  diagonal  ele-
	       ments of L are not stored.

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

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

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

       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, so the
	       solution could not be computed.

LAPACK version 3.0						   15 June 2000 							  DGESV(l)

dgesv.f(3)							      LAPACK								dgesv.f(3)

NAME

       dgesv.f -

SYNOPSIS

   Functions/Subroutines
       subroutine dgesv (N, NRHS, A, LDA, IPIV, B, LDB, INFO)
	    DGESV computes the solution to system of linear equations A * X = B for GE matrices

Function/Subroutine Documentation
   subroutine dgesv (integerN, integerNRHS, double precision, dimension( lda, * )A, integerLDA, integer, dimension( * )IPIV, double precision,
       dimension( ldb, * )B, integerLDB, integerINFO)
	DGESV computes the solution to system of linear equations A * X = B for GE matrices

       Purpose:

	    DGESV computes the solution to a real system of linear equations
	       A * X = B,
	    where A is an N-by-N matrix 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 = P * L * U,
	    where P is a permutation matrix, L is unit lower triangular, and U is
	    upper triangular.  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.

	   NRHS

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

	   A

		     A is DOUBLE PRECISION array, dimension (LDA,N)
		     On entry, the N-by-N coefficient matrix A.
		     On exit, the factors L and U from the factorization
		     A = P*L*U; the unit diagonal elements of L are not stored.

	   LDA

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

	   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 matrix of 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, so the solution could not be computed.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   November 2011

       Definition at line 123 of file dgesv.f.

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

Version 3.4.1							  Sun May 26 2013							dgesv.f(3)