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SUBROUTINE <a name="DORGTR.1"></a><a href="dorgtr.f.html#DORGTR.1">DORGTR</a>( UPLO, N, A, LDA, TAU, WORK, LWORK, INFO )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> -- LAPACK routine (version 3.1) --
</span><span class="comment">*</span><span class="comment"> Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
</span><span class="comment">*</span><span class="comment"> November 2006
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> .. Scalar Arguments ..
</span> CHARACTER UPLO
INTEGER INFO, LDA, LWORK, N
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Array Arguments ..
</span> DOUBLE PRECISION A( LDA, * ), TAU( * ), WORK( * )
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Purpose
</span><span class="comment">*</span><span class="comment"> =======
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> <a name="DORGTR.18"></a><a href="dorgtr.f.html#DORGTR.1">DORGTR</a> generates a real orthogonal matrix Q which is defined as the
</span><span class="comment">*</span><span class="comment"> product of n-1 elementary reflectors of order N, as returned by
</span><span class="comment">*</span><span class="comment"> <a name="DSYTRD.20"></a><a href="dsytrd.f.html#DSYTRD.1">DSYTRD</a>:
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> if UPLO = 'U', Q = H(n-1) . . . H(2) H(1),
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> if UPLO = 'L', Q = H(1) H(2) . . . H(n-1).
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Arguments
</span><span class="comment">*</span><span class="comment"> =========
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> UPLO (input) CHARACTER*1
</span><span class="comment">*</span><span class="comment"> = 'U': Upper triangle of A contains elementary reflectors
</span><span class="comment">*</span><span class="comment"> from <a name="DSYTRD.31"></a><a href="dsytrd.f.html#DSYTRD.1">DSYTRD</a>;
</span><span class="comment">*</span><span class="comment"> = 'L': Lower triangle of A contains elementary reflectors
</span><span class="comment">*</span><span class="comment"> from <a name="DSYTRD.33"></a><a href="dsytrd.f.html#DSYTRD.1">DSYTRD</a>.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> N (input) INTEGER
</span><span class="comment">*</span><span class="comment"> The order of the matrix Q. N >= 0.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
</span><span class="comment">*</span><span class="comment"> On entry, the vectors which define the elementary reflectors,
</span><span class="comment">*</span><span class="comment"> as returned by <a name="DSYTRD.40"></a><a href="dsytrd.f.html#DSYTRD.1">DSYTRD</a>.
</span><span class="comment">*</span><span class="comment"> On exit, the N-by-N orthogonal matrix Q.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> LDA (input) INTEGER
</span><span class="comment">*</span><span class="comment"> The leading dimension of the array A. LDA >= max(1,N).
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> TAU (input) DOUBLE PRECISION array, dimension (N-1)
</span><span class="comment">*</span><span class="comment"> TAU(i) must contain the scalar factor of the elementary
</span><span class="comment">*</span><span class="comment"> reflector H(i), as returned by <a name="DSYTRD.48"></a><a href="dsytrd.f.html#DSYTRD.1">DSYTRD</a>.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> WORK (workspace/output) DOUBLE PRECISION array, dimension (MAX(1,LWORK))
</span><span class="comment">*</span><span class="comment"> On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> LWORK (input) INTEGER
</span><span class="comment">*</span><span class="comment"> The dimension of the array WORK. LWORK >= max(1,N-1).
</span><span class="comment">*</span><span class="comment"> For optimum performance LWORK >= (N-1)*NB, where NB is
</span><span class="comment">*</span><span class="comment"> the optimal blocksize.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> If LWORK = -1, then a workspace query is assumed; the routine
</span><span class="comment">*</span><span class="comment"> only calculates the optimal size of the WORK array, returns
</span><span class="comment">*</span><span class="comment"> this value as the first entry of the WORK array, and no error
</span><span class="comment">*</span><span class="comment"> message related to LWORK is issued by <a name="XERBLA.61"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> INFO (output) INTEGER
</span><span class="comment">*</span><span class="comment"> = 0: successful exit
</span><span class="comment">*</span><span class="comment"> < 0: if INFO = -i, the i-th argument had an illegal value
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> =====================================================================
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> .. Parameters ..
</span> DOUBLE PRECISION ZERO, ONE
PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0 )
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Local Scalars ..
</span> LOGICAL LQUERY, UPPER
INTEGER I, IINFO, J, LWKOPT, NB
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. External Functions ..
</span> LOGICAL <a name="LSAME.78"></a><a href="lsame.f.html#LSAME.1">LSAME</a>
INTEGER <a name="ILAENV.79"></a><a href="hfy-index.html#ILAENV">ILAENV</a>
EXTERNAL <a name="LSAME.80"></a><a href="lsame.f.html#LSAME.1">LSAME</a>, <a name="ILAENV.80"></a><a href="hfy-index.html#ILAENV">ILAENV</a>
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. External Subroutines ..
</span> EXTERNAL <a name="DORGQL.83"></a><a href="dorgql.f.html#DORGQL.1">DORGQL</a>, <a name="DORGQR.83"></a><a href="dorgqr.f.html#DORGQR.1">DORGQR</a>, <a name="XERBLA.83"></a><a href="xerbla.f.html#XERBLA.1">XERBLA</a>
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Intrinsic Functions ..
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