3 * =========== DOCUMENTATION ===========
5 * Online html documentation available at
6 * http://www.netlib.org/lapack/explore-html/
11 * DOUBLE PRECISION FUNCTION DRZT02( M, N, AF, LDA, TAU, WORK,
14 * .. Scalar Arguments ..
15 * INTEGER LDA, LWORK, M, N
17 * .. Array Arguments ..
18 * DOUBLE PRECISION AF( LDA, * ), TAU( * ), WORK( LWORK )
28 *> || I - Q'*Q || / ( M * eps)
29 *> where the matrix Q is defined by the Householder transformations
30 *> generated by DTZRZF.
39 *> The number of rows of the matrix AF.
45 *> The number of columns of the matrix AF.
50 *> AF is DOUBLE PRECISION array, dimension (LDA,N)
51 *> The output of DTZRZF.
57 *> The leading dimension of the array AF.
62 *> TAU is DOUBLE PRECISION array, dimension (M)
63 *> Details of the Householder transformations as returned by
69 *> WORK is DOUBLE PRECISION array, dimension (LWORK)
75 *> length of WORK array. LWORK >= N*N+N*NB.
81 *> \author Univ. of Tennessee
82 *> \author Univ. of California Berkeley
83 *> \author Univ. of Colorado Denver
86 *> \date November 2011
88 *> \ingroup double_lin
90 * =====================================================================
91 DOUBLE PRECISION FUNCTION DRZT02( M, N, AF, LDA, TAU, WORK,
94 * -- LAPACK test routine (version 3.4.0) --
95 * -- LAPACK is a software package provided by Univ. of Tennessee, --
96 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
99 * .. Scalar Arguments ..
100 INTEGER LDA, LWORK, M, N
102 * .. Array Arguments ..
103 DOUBLE PRECISION AF( LDA, * ), TAU( * ), WORK( LWORK )
106 * =====================================================================
109 DOUBLE PRECISION ZERO, ONE
110 PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0 )
112 * .. Local Scalars ..
116 DOUBLE PRECISION RWORK( 1 )
118 * .. External Functions ..
119 DOUBLE PRECISION DLAMCH, DLANGE
120 EXTERNAL DLAMCH, DLANGE
122 * .. External Subroutines ..
123 EXTERNAL DLASET, DORMRZ, XERBLA
125 * .. Intrinsic Functions ..
128 * .. Executable Statements ..
132 IF( LWORK.LT.N*N+N ) THEN
133 CALL XERBLA( 'DRZT02', 7 )
137 * Quick return if possible
139 IF( M.LE.0 .OR. N.LE.0 )
144 CALL DLASET( 'Full', N, N, ZERO, ONE, WORK, N )
146 * Q := P(1) * ... * P(m) * Q
148 CALL DORMRZ( 'Left', 'No transpose', N, N, M, N-M, AF, LDA, TAU,
149 $ WORK, N, WORK( N*N+1 ), LWORK-N*N, INFO )
151 * Q := P(m) * ... * P(1) * Q
153 CALL DORMRZ( 'Left', 'Transpose', N, N, M, N-M, AF, LDA, TAU,
154 $ WORK, N, WORK( N*N+1 ), LWORK-N*N, INFO )
159 WORK( ( I-1 )*N+I ) = WORK( ( I-1 )*N+I ) - ONE
162 DRZT02 = DLANGE( 'One-norm', N, N, WORK, N, RWORK ) /
163 $ ( DLAMCH( 'Epsilon' )*DBLE( MAX( M, N ) ) )