1       SUBROUTINE DRQT01( M, N, A, AF, Q, R, LDA, TAU, WORK, LWORK,
  2      $                   RWORK, RESULT )
  3 *
  4 *  -- LAPACK test routine (version 3.1) --
  5 *     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
  6 *     November 2006
  7 *
  8 *     .. Scalar Arguments ..
  9       INTEGER            LDA, LWORK, M, N
 10 *     ..
 11 *     .. Array Arguments ..
 12       DOUBLE PRECISION   A( LDA, * ), AF( LDA, * ), Q( LDA, * ),
 13      $                   R( LDA, * ), RESULT* ), RWORK( * ), TAU( * ),
 14      $                   WORK( LWORK )
 15 *     ..
 16 *
 17 *  Purpose
 18 *  =======
 19 *
 20 *  DRQT01 tests DGERQF, which computes the RQ factorization of an m-by-n
 21 *  matrix A, and partially tests DORGRQ which forms the n-by-n
 22 *  orthogonal matrix Q.
 23 *
 24 *  DRQT01 compares R with A*Q', and checks that Q is orthogonal.
 25 *
 26 *  Arguments
 27 *  =========
 28 *
 29 *  M       (input) INTEGER
 30 *          The number of rows of the matrix A.  M >= 0.
 31 *
 32 *  N       (input) INTEGER
 33 *          The number of columns of the matrix A.  N >= 0.
 34 *
 35 *  A       (input) DOUBLE PRECISION array, dimension (LDA,N)
 36 *          The m-by-n matrix A.
 37 *
 38 *  AF      (output) DOUBLE PRECISION array, dimension (LDA,N)
 39 *          Details of the RQ factorization of A, as returned by DGERQF.
 40 *          See DGERQF for further details.
 41 *
 42 *  Q       (output) DOUBLE PRECISION array, dimension (LDA,N)
 43 *          The n-by-n orthogonal matrix Q.
 44 *
 45 *  R       (workspace) DOUBLE PRECISION array, dimension (LDA,max(M,N))
 46 *
 47 *  LDA     (input) INTEGER
 48 *          The leading dimension of the arrays A, AF, Q and L.
 49 *          LDA >= max(M,N).
 50 *
 51 *  TAU     (output) DOUBLE PRECISION array, dimension (min(M,N))
 52 *          The scalar factors of the elementary reflectors, as returned
 53 *          by DGERQF.
 54 *
 55 *  WORK    (workspace) DOUBLE PRECISION array, dimension (LWORK)
 56 *
 57 *  LWORK   (input) INTEGER
 58 *          The dimension of the array WORK.
 59 *
 60 *  RWORK   (workspace) DOUBLE PRECISION array, dimension (max(M,N))
 61 *
 62 *  RESULT  (output) DOUBLE PRECISION array, dimension (2)
 63 *          The test ratios:
 64 *          RESULT(1) = norm( R - A*Q' ) / ( N * norm(A) * EPS )
 65 *          RESULT(2) = norm( I - Q*Q' ) / ( N * EPS )
 66 *
 67 *  =====================================================================
 68 *
 69 *     .. Parameters ..
 70       DOUBLE PRECISION   ZERO, ONE
 71       PARAMETER          ( ZERO = 0.0D+0, ONE = 1.0D+0 )
 72       DOUBLE PRECISION   ROGUE
 73       PARAMETER          ( ROGUE = -1.0D+10 )
 74 *     ..
 75 *     .. Local Scalars ..
 76       INTEGER            INFO, MINMN
 77       DOUBLE PRECISION   ANORM, EPS, RESID
 78 *     ..
 79 *     .. External Functions ..
 80       DOUBLE PRECISION   DLAMCH, DLANGE, DLANSY
 81       EXTERNAL           DLAMCH, DLANGE, DLANSY
 82 *     ..
 83 *     .. External Subroutines ..
 84       EXTERNAL           DGEMM, DGERQF, DLACPY, DLASET, DORGRQ, DSYRK
 85 *     ..
 86 *     .. Intrinsic Functions ..
 87       INTRINSIC          DBLEMAXMIN
 88 *     ..
 89 *     .. Scalars in Common ..
 90       CHARACTER*32       SRNAMT
 91 *     ..
 92 *     .. Common blocks ..
 93       COMMON             / SRNAMC / SRNAMT
 94 *     ..
 95 *     .. Executable Statements ..
 96 *
 97       MINMN = MIN( M, N )
 98       EPS = DLAMCH( 'Epsilon' )
 99 *
100 *     Copy the matrix A to the array AF.
101 *
102       CALL DLACPY( 'Full', M, N, A, LDA, AF, LDA )
103 *
104 *     Factorize the matrix A in the array AF.
105 *
106       SRNAMT = 'DGERQF'
107       CALL DGERQF( M, N, AF, LDA, TAU, WORK, LWORK, INFO )
108 *
109 *     Copy details of Q
110 *
111       CALL DLASET( 'Full', N, N, ROGUE, ROGUE, Q, LDA )
112       IF( M.LE.N ) THEN
113          IF( M.GT.0 .AND. M.LT.N )
114      $      CALL DLACPY( 'Full', M, N-M, AF, LDA, Q( N-M+11 ), LDA )
115          IF( M.GT.1 )
116      $      CALL DLACPY( 'Lower', M-1, M-1, AF( 2, N-M+1 ), LDA,
117      $                   Q( N-M+2, N-M+1 ), LDA )
118       ELSE
119          IF( N.GT.1 )
120      $      CALL DLACPY( 'Lower', N-1, N-1, AF( M-N+21 ), LDA,
121      $                   Q( 21 ), LDA )
122       END IF
123 *
124 *     Generate the n-by-n matrix Q
125 *
126       SRNAMT = 'DORGRQ'
127       CALL DORGRQ( N, N, MINMN, Q, LDA, TAU, WORK, LWORK, INFO )
128 *
129 *     Copy R
130 *
131       CALL DLASET( 'Full', M, N, ZERO, ZERO, R, LDA )
132       IF( M.LE.N ) THEN
133          IF( M.GT.0 )
134      $      CALL DLACPY( 'Upper', M, M, AF( 1, N-M+1 ), LDA,
135      $                   R( 1, N-M+1 ), LDA )
136       ELSE
137          IF( M.GT..AND. N.GT.0 )
138      $      CALL DLACPY( 'Full', M-N, N, AF, LDA, R, LDA )
139          IF( N.GT.0 )
140      $      CALL DLACPY( 'Upper', N, N, AF( M-N+11 ), LDA,
141      $                   R( M-N+11 ), LDA )
142       END IF
143 *
144 *     Compute R - A*Q'
145 *
146       CALL DGEMM( 'No transpose''Transpose', M, N, N, -ONE, A, LDA, Q,
147      $            LDA, ONE, R, LDA )
148 *
149 *     Compute norm( R - Q'*A ) / ( N * norm(A) * EPS ) .
150 *
151       ANORM = DLANGE( '1', M, N, A, LDA, RWORK )
152       RESID = DLANGE( '1', M, N, R, LDA, RWORK )
153       IF( ANORM.GT.ZERO ) THEN
154          RESULT1 ) = ( ( RESID / DBLEMAX1, N ) ) ) / ANORM ) / EPS
155       ELSE
156          RESULT1 ) = ZERO
157       END IF
158 *
159 *     Compute I - Q*Q'
160 *
161       CALL DLASET( 'Full', N, N, ZERO, ONE, R, LDA )
162       CALL DSYRK( 'Upper''No transpose', N, N, -ONE, Q, LDA, ONE, R,
163      $            LDA )
164 *
165 *     Compute norm( I - Q*Q' ) / ( N * EPS ) .
166 *
167       RESID = DLANSY( '1''Upper', N, R, LDA, RWORK )
168 *
169       RESULT2 ) = ( RESID / DBLEMAX1, N ) ) ) / EPS
170 *
171       RETURN
172 *
173 *     End of DRQT01
174 *
175       END