NAME

       dorgqr.f -

SYNOPSIS

   Functions/Subroutines
       subroutine dorgqr (M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
           DORGQR

Function/Subroutine Documentation

   subroutine dorgqr (integer M, integer N, integer K, double precision, dimension( lda, * ) A,
       integer LDA, double precision, dimension( * ) TAU, double precision, dimension( * ) WORK,
       integer LWORK, integer INFO)
       DORGQR

       Purpose:

            DORGQR generates an M-by-N real matrix Q with orthonormal columns,
            which is defined as the first N columns of a product of K elementary
            reflectors of order M

                  Q  =  H(1) H(2) . . . H(k)

            as returned by DGEQRF.

       Parameters:
           M

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

           N

                     N is INTEGER
                     The number of columns of the matrix Q. M >= N >= 0.

           K

                     K is INTEGER
                     The number of elementary reflectors whose product defines the
                     matrix Q. N >= K >= 0.

           A

                     A is DOUBLE PRECISION array, dimension (LDA,N)
                     On entry, the i-th column must contain the vector which
                     defines the elementary reflector H(i), for i = 1,2,...,k, as
                     returned by DGEQRF in the first k columns of its array
                     argument A.
                     On exit, the M-by-N matrix Q.

           LDA

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

           TAU

                     TAU is DOUBLE PRECISION array, dimension (K)
                     TAU(i) must contain the scalar factor of the elementary
                     reflector H(i), as returned by DGEQRF.

           WORK

                     WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))
                     On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

           LWORK

                     LWORK is INTEGER
                     The dimension of the array WORK. LWORK >= max(1,N).
                     For optimum performance LWORK >= N*NB, where NB is the
                     optimal blocksize.

                     If LWORK = -1, then a workspace query is assumed; the routine
                     only calculates the optimal size of the WORK array, returns
                     this value as the first entry of the WORK array, and no error
                     message related to LWORK is issued by XERBLA.

           INFO

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

       Author:
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Date:
           November 2011

Author

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