NAME

       dorgtr.f -

SYNOPSIS

   Functions/Subroutines
       subroutine dorgtr (UPLO, N, A, LDA, TAU, WORK, LWORK, INFO)
           DORGTR

Function/Subroutine Documentation

   subroutine dorgtr (character UPLO, integer N, double precision, dimension( lda, * ) A, integer
       LDA, double precision, dimension( * ) TAU, double precision, dimension( * ) WORK, integer
       LWORK, integer INFO)
       DORGTR

       Purpose:

            DORGTR generates a real orthogonal matrix Q which is defined as the
            product of n-1 elementary reflectors of order N, as returned by
            DSYTRD:

            if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),

            if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).

       Parameters:
           UPLO

                     UPLO is CHARACTER*1
                     = 'U': Upper triangle of A contains elementary reflectors
                            from DSYTRD;
                     = 'L': Lower triangle of A contains elementary reflectors
                            from DSYTRD.

           N

                     N is INTEGER
                     The order of the matrix Q. N >= 0.

           A

                     A is DOUBLE PRECISION array, dimension (LDA,N)
                     On entry, the vectors which define the elementary reflectors,
                     as returned by DSYTRD.
                     On exit, the N-by-N orthogonal matrix Q.

           LDA

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

           TAU

                     TAU is DOUBLE PRECISION array, dimension (N-1)
                     TAU(i) must contain the scalar factor of the elementary
                     reflector H(i), as returned by DSYTRD.

           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-1).
                     For optimum performance LWORK >= (N-1)*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 had 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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