SRC/dgesv.f(3)

NAME
SRC/dgesv.f

SYNOPSIS

  Functions/Subroutines
subroutine dgesv (n, nrhs, a, lda, ipiv, b, ldb, info)

Function/Subroutine Documentation

  subroutine dgesv (integer n, integer nrhs, double precision, dimension( lda, * ) a, integer lda, integer, dimension( * ) ipiv, double precision, dimension( ldb, * ) b, integer ldb, integer info)

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.

Definition at line 123 of file dgesv.f.

Author

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