cgelq2.f(3)

NAME
cgelq2.f -

SYNOPSIS

  Functions/Subroutines
subroutine cgelq2 (M, N, A, LDA, TAU, WORK, INFO)
CGELQ2 computes the LQ factorization of a general rectangular matrix using an unblocked algorithm.

Function/Subroutine Documentation

  subroutine cgelq2 (integerM, integerN, complex, dimension( lda, * )A, integerLDA, complex, dimension( * )TAU, complex, dimension( * )WORK, integerINFO)

CGELQ2 computes the LQ factorization of a general rectangular matrix using an unblocked algorithm.

Purpose:

     CGELQ2 computes an LQ factorization of a complex m by n matrix A:
     A = L * Q.

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 A.
              On exit, the elements on and below the diagonal of the array
              contain the m by min(m,n) lower trapezoidal matrix L (L is
              lower triangular if m <= n); the elements above the diagonal,
              with the array TAU, represent the unitary matrix Q as a
              product of elementary reflectors (see Further Details).

    LDA

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

    TAU

              TAU is COMPLEX array, dimension (min(M,N))
              The scalar factors of the elementary reflectors (see Further
              Details).

    WORK

              WORK is COMPLEX array, dimension (M)

    INFO

              INFO is INTEGER
              = 0: successful exit
              < 0: if INFO = -i, the i-th argument had an illegal value

Author:
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Date:
    September 2012

Further Details:

      The matrix Q is represented as a product of elementary reflectors
         Q = H(k)**H . . . H(2)**H H(1)**H, where k = min(m,n).
      Each H(i) has the form
         H(i) = I - tau * v * v**H
      where tau is a complex scalar, and v is a complex vector with
      v(1:i-1) = 0 and v(i) = 1; conjg(v(i+1:n)) is stored on exit in
      A(i,i+1:n), and tau in TAU(i).

Definition at line 122 of file cgelq2.f.

Author

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