dgesv-f(3)

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 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 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 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

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