getf2(3)

NAME
getf2 - getf2: triangular factor panel, level 2

SYNOPSIS

  Functions

subroutine cgetf2 (m, n, a, lda, ipiv, info)
CGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row interchanges (unblocked algorithm).
subroutine dgetf2 (m, n, a, lda, ipiv, info)
DGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row interchanges (unblocked algorithm).
subroutine sgetf2 (m, n, a, lda, ipiv, info)
SGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row interchanges (unblocked algorithm).
subroutine zgetf2 (m, n, a, lda, ipiv, info)
ZGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row interchanges (unblocked algorithm).

Detailed Description

Function Documentation

  subroutine cgetf2 (integer m, integer n, complex, dimension( lda, * ) a, integer lda, integer, dimension( * ) ipiv, integer info)

CGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row interchanges (unblocked algorithm).

Purpose:

    !>
    !> CGETF2 computes an LU factorization of a general m-by-n matrix A
    !> using partial pivoting with row interchanges.
    !>
    !> The factorization has the form
    !>    A = P * L * U
    !> where P is a permutation matrix, L is lower triangular with unit
    !> diagonal elements (lower trapezoidal if m > n), and U is upper
    !> triangular (upper trapezoidal if m < n).
    !>
    !> This is the right-looking Level 2 BLAS version of the algorithm.
    !>

Parameters
    M

    !>          M is INTEGER
    !>          The number of rows of the matrix A.  M >= 0.
    !>

    N

    !>          N is INTEGER
    !>          The number of columns of the matrix A.  N >= 0.
    !>

    A

    !>          A is COMPLEX array, dimension (LDA,N)
    !>          On entry, the m by n matrix to be factored.
    !>          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,M).
    !>

    IPIV

    !>          IPIV is 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

    !>          INFO is INTEGER
    !>          = 0: successful exit
    !>          < 0: if INFO = -k, the k-th argument had an illegal value
    !>          > 0: if INFO = k, U(k,k) 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.
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

  subroutine dgetf2 (integer m, integer n, double precision, dimension( lda, * ) a, integer lda, integer, dimension( * ) ipiv, integer info)

DGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row interchanges (unblocked algorithm).

Purpose:

    !>
    !> DGETF2 computes an LU factorization of a general m-by-n matrix A
    !> using partial pivoting with row interchanges.
    !>
    !> The factorization has the form
    !>    A = P * L * U
    !> where P is a permutation matrix, L is lower triangular with unit
    !> diagonal elements (lower trapezoidal if m > n), and U is upper
    !> triangular (upper trapezoidal if m < n).
    !>
    !> This is the right-looking Level 2 BLAS version of the algorithm.
    !>

Parameters
    M

    !>          M is INTEGER
    !>          The number of rows of the matrix A.  M >= 0.
    !>

    N

    !>          N is INTEGER
    !>          The number of columns of the matrix A.  N >= 0.
    !>

    A

    !>          A is DOUBLE PRECISION array, dimension (LDA,N)
    !>          On entry, the m by n matrix to be factored.
    !>          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,M).
    !>

    IPIV

    !>          IPIV is 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

    !>          INFO is INTEGER
    !>          = 0: successful exit
    !>          < 0: if INFO = -k, the k-th argument had an illegal value
    !>          > 0: if INFO = k, U(k,k) 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.
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

  subroutine sgetf2 (integer m, integer n, real, dimension( lda, * ) a, integer lda, integer, dimension( * ) ipiv, integer info)

SGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row interchanges (unblocked algorithm).

Purpose:

    !>
    !> SGETF2 computes an LU factorization of a general m-by-n matrix A
    !> using partial pivoting with row interchanges.
    !>
    !> The factorization has the form
    !>    A = P * L * U
    !> where P is a permutation matrix, L is lower triangular with unit
    !> diagonal elements (lower trapezoidal if m > n), and U is upper
    !> triangular (upper trapezoidal if m < n).
    !>
    !> This is the right-looking Level 2 BLAS version of the algorithm.
    !>

Parameters
    M

    !>          M is INTEGER
    !>          The number of rows of the matrix A.  M >= 0.
    !>

    N

    !>          N is INTEGER
    !>          The number of columns of the matrix A.  N >= 0.
    !>

    A

    !>          A is REAL array, dimension (LDA,N)
    !>          On entry, the m by n matrix to be factored.
    !>          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,M).
    !>

    IPIV

    !>          IPIV is 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

    !>          INFO is INTEGER
    !>          = 0: successful exit
    !>          < 0: if INFO = -k, the k-th argument had an illegal value
    !>          > 0: if INFO = k, U(k,k) 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.
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

  subroutine zgetf2 (integer m, integer n, complex*16, dimension( lda, * ) a, integer lda, integer, dimension( * ) ipiv, integer info)

ZGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row interchanges (unblocked algorithm).

Purpose:

    !>
    !> ZGETF2 computes an LU factorization of a general m-by-n matrix A
    !> using partial pivoting with row interchanges.
    !>
    !> The factorization has the form
    !>    A = P * L * U
    !> where P is a permutation matrix, L is lower triangular with unit
    !> diagonal elements (lower trapezoidal if m > n), and U is upper
    !> triangular (upper trapezoidal if m < n).
    !>
    !> This is the right-looking Level 2 BLAS version of the algorithm.
    !>

Parameters
    M

    !>          M is INTEGER
    !>          The number of rows of the matrix A.  M >= 0.
    !>

    N

    !>          N is INTEGER
    !>          The number of columns of the matrix A.  N >= 0.
    !>

    A

    !>          A is COMPLEX*16 array, dimension (LDA,N)
    !>          On entry, the m by n matrix to be factored.
    !>          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,M).
    !>

    IPIV

    !>          IPIV is 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

    !>          INFO is INTEGER
    !>          = 0: successful exit
    !>          < 0: if INFO = -k, the k-th argument had an illegal value
    !>          > 0: if INFO = k, U(k,k) 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.
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Author

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