Provided by: liblapack-doc_3.3.1-1_all bug

NAME

       LAPACK-3 - computes an RQ factorization of a real m by n matrix A

SYNOPSIS

       SUBROUTINE DGERQ2( M, N, A, LDA, TAU, WORK, INFO )

           INTEGER        INFO, LDA, M, N

           DOUBLE         PRECISION A( LDA, * ), TAU( * ), WORK( * )

PURPOSE

       DGERQ2 computes an RQ factorization of a real m by n matrix A:
        A = R * Q.

ARGUMENTS

        M       (input) INTEGER
                The number of rows of the matrix A.  M >= 0.

        N       (input) INTEGER
                The number of columns of the matrix A.  N >= 0.

        A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
                On entry, the m by n matrix A.
                On exit, if m <= n, the upper triangle of the subarray
                A(1:m,n-m+1:n) contains the m by m upper triangular matrix R;
                if m >= n, the elements on and above the (m-n)-th subdiagonal
                contain the m by n upper trapezoidal matrix R; the remaining
                elements, with the array TAU, represent the orthogonal matrix
                Q as a product of elementary reflectors (see Further
                Details).

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

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

        WORK    (workspace) DOUBLE PRECISION array, dimension (M)

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

FURTHER DETAILS

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

 LAPACK routine (version 3.3.1)             April 2011                            DGERQ2(3lapack)