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NAME
     dorgtr - generate  a  real  orthogonal  matrix  Q  which  is
     defined as the product of n-1 elementary reflectors of order
     N, as returned by DSYTRD

SYNOPSIS
     SUBROUTINE DORGTR( UPLO, N, A, LDA, TAU, WORK, LWORK, INFO )

     CHARACTER UPLO

     INTEGER INFO, LDA, LWORK, N

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



     #include <sunperf.h>

     void dorgtr(char uplo, int n, double *da,  int  lda,  double
               *tau, int *info) ;

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).


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

     N         (input) INTEGER
               The order of the matrix Q. N >= 0.

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

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

     WORK      (workspace/output) DOUBLE PRECISION array,  dimen-
               sion (LWORK)
               On exit, if INFO = 0, WORK(1) returns the  optimal
               LWORK.

     LWORK     (input) 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.

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

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