1       SUBROUTINE DGRQTS( M, P, N, A, AF, Q, R, LDA, TAUA, B, BF, Z, T,
  2      $                   BWK, LDB, TAUB, WORK, LWORK, 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, LDB, LWORK, M, N, P
 10 *     ..
 11 *     .. Array Arguments ..
 12       DOUBLE PRECISION   A( LDA, * ), AF( LDA, * ), B( LDB, * ),
 13      $                   BF( LDB, * ), BWK( LDB, * ), Q( LDA, * ),
 14      $                   R( LDA, * ), RESULT4 ), RWORK( * ),
 15      $                   T( LDB, * ), TAUA( * ), TAUB( * ),
 16      $                   WORK( LWORK ), Z( LDB, * )
 17 *     ..
 18 *
 19 *  Purpose
 20 *  =======
 21 *
 22 *  DGRQTS tests DGGRQF, which computes the GRQ factorization of an
 23 *  M-by-N matrix A and a P-by-N matrix B: A = R*Q and B = Z*T*Q.
 24 *
 25 *  Arguments
 26 *  =========
 27 *
 28 *  M       (input) INTEGER
 29 *          The number of rows of the matrix A.  M >= 0.
 30 *
 31 *  P       (input) INTEGER
 32 *          The number of rows of the matrix B.  P >= 0.
 33 *
 34 *  N       (input) INTEGER
 35 *          The number of columns of the matrices A and B.  N >= 0.
 36 *
 37 *  A       (input) DOUBLE PRECISION array, dimension (LDA,N)
 38 *          The M-by-N matrix A.
 39 *
 40 *  AF      (output) DOUBLE PRECISION array, dimension (LDA,N)
 41 *          Details of the GRQ factorization of A and B, as returned
 42 *          by DGGRQF, see SGGRQF for further details.
 43 *
 44 *  Q       (output) DOUBLE PRECISION array, dimension (LDA,N)
 45 *          The N-by-N orthogonal matrix Q.
 46 *
 47 *  R       (workspace) DOUBLE PRECISION array, dimension (LDA,MAX(M,N))
 48 *
 49 *  LDA     (input) INTEGER
 50 *          The leading dimension of the arrays A, AF, R and Q.
 51 *          LDA >= max(M,N).
 52 *
 53 *  TAUA    (output) DOUBLE PRECISION array, dimension (min(M,N))
 54 *          The scalar factors of the elementary reflectors, as returned
 55 *          by DGGQRC.
 56 *
 57 *  B       (input) DOUBLE PRECISION array, dimension (LDB,N)
 58 *          On entry, the P-by-N matrix A.
 59 *
 60 *  BF      (output) DOUBLE PRECISION array, dimension (LDB,N)
 61 *          Details of the GQR factorization of A and B, as returned
 62 *          by DGGRQF, see SGGRQF for further details.
 63 *
 64 *  Z       (output) DOUBLE PRECISION array, dimension (LDB,P)
 65 *          The P-by-P orthogonal matrix Z.
 66 *
 67 *  T       (workspace) DOUBLE PRECISION array, dimension (LDB,max(P,N))
 68 *
 69 *  BWK     (workspace) DOUBLE PRECISION array, dimension (LDB,N)
 70 *
 71 *  LDB     (input) INTEGER
 72 *          The leading dimension of the arrays B, BF, Z and T.
 73 *          LDB >= max(P,N).
 74 *
 75 *  TAUB    (output) DOUBLE PRECISION array, dimension (min(P,N))
 76 *          The scalar factors of the elementary reflectors, as returned
 77 *          by DGGRQF.
 78 *
 79 *  WORK    (workspace) DOUBLE PRECISION array, dimension (LWORK)
 80 *
 81 *  LWORK   (input) INTEGER
 82 *          The dimension of the array WORK, LWORK >= max(M,P,N)**2.
 83 *
 84 *  RWORK   (workspace) DOUBLE PRECISION array, dimension (M)
 85 *
 86 *  RESULT  (output) DOUBLE PRECISION array, dimension (4)
 87 *          The test ratios:
 88 *            RESULT(1) = norm( R - A*Q' ) / ( MAX(M,N)*norm(A)*ULP)
 89 *            RESULT(2) = norm( T*Q - Z'*B ) / (MAX(P,N)*norm(B)*ULP)
 90 *            RESULT(3) = norm( I - Q'*Q ) / ( N*ULP )
 91 *            RESULT(4) = norm( I - Z'*Z ) / ( P*ULP )
 92 *
 93 *  =====================================================================
 94 *
 95 *     .. Parameters ..
 96       DOUBLE PRECISION   ZERO, ONE
 97       PARAMETER          ( ZERO = 0.0D+0, ONE = 1.0D+0 )
 98       DOUBLE PRECISION   ROGUE
 99       PARAMETER          ( ROGUE = -1.0D+10 )
100 *     ..
101 *     .. Local Scalars ..
102       INTEGER            INFO
103       DOUBLE PRECISION   ANORM, BNORM, RESID, ULP, UNFL
104 *     ..
105 *     .. External Functions ..
106       DOUBLE PRECISION   DLAMCH, DLANGE, DLANSY
107       EXTERNAL           DLAMCH, DLANGE, DLANSY
108 *     ..
109 *     .. External Subroutines ..
110       EXTERNAL           DGEMM, DGGRQF, DLACPY, DLASET, DORGQR, DORGRQ,
111      $                   DSYRK
112 *     ..
113 *     .. Intrinsic Functions ..
114       INTRINSIC          DBLEMAXMIN
115 *     ..
116 *     .. Executable Statements ..
117 *
118       ULP = DLAMCH( 'Precision' )
119       UNFL = DLAMCH( 'Safe minimum' )
120 *
121 *     Copy the matrix A to the array AF.
122 *
123       CALL DLACPY( 'Full', M, N, A, LDA, AF, LDA )
124       CALL DLACPY( 'Full', P, N, B, LDB, BF, LDB )
125 *
126       ANORM = MAX( DLANGE( '1', M, N, A, LDA, RWORK ), UNFL )
127       BNORM = MAX( DLANGE( '1', P, N, B, LDB, RWORK ), UNFL )
128 *
129 *     Factorize the matrices A and B in the arrays AF and BF.
130 *
131       CALL DGGRQF( M, P, N, AF, LDA, TAUA, BF, LDB, TAUB, WORK, LWORK,
132      $             INFO )
133 *
134 *     Generate the N-by-N matrix Q
135 *
136       CALL DLASET( 'Full', N, N, ROGUE, ROGUE, Q, LDA )
137       IF( M.LE.N ) THEN
138          IF( M.GT.0 .AND. M.LT.N )
139      $      CALL DLACPY( 'Full', M, N-M, AF, LDA, Q( N-M+11 ), LDA )
140          IF( M.GT.1 )
141      $      CALL DLACPY( 'Lower', M-1, M-1, AF( 2, N-M+1 ), LDA,
142      $                   Q( N-M+2, N-M+1 ), LDA )
143       ELSE
144          IF( N.GT.1 )
145      $      CALL DLACPY( 'Lower', N-1, N-1, AF( M-N+21 ), LDA,
146      $                   Q( 21 ), LDA )
147       END IF
148       CALL DORGRQ( N, N, MIN( M, N ), Q, LDA, TAUA, WORK, LWORK, INFO )
149 *
150 *     Generate the P-by-P matrix Z
151 *
152       CALL DLASET( 'Full', P, P, ROGUE, ROGUE, Z, LDB )
153       IF( P.GT.1 )
154      $   CALL DLACPY( 'Lower', P-1, N, BF( 21 ), LDB, Z( 21 ), LDB )
155       CALL DORGQR( P, P, MIN( P, N ), Z, LDB, TAUB, WORK, LWORK, INFO )
156 *
157 *     Copy R
158 *
159       CALL DLASET( 'Full', M, N, ZERO, ZERO, R, LDA )
160       IF( M.LE.N ) THEN
161          CALL DLACPY( 'Upper', M, M, AF( 1, N-M+1 ), LDA, R( 1, N-M+1 ),
162      $                LDA )
163       ELSE
164          CALL DLACPY( 'Full', M-N, N, AF, LDA, R, LDA )
165          CALL DLACPY( 'Upper', N, N, AF( M-N+11 ), LDA, R( M-N+11 ),
166      $                LDA )
167       END IF
168 *
169 *     Copy T
170 *
171       CALL DLASET( 'Full', P, N, ZERO, ZERO, T, LDB )
172       CALL DLACPY( 'Upper', P, N, BF, LDB, T, LDB )
173 *
174 *     Compute R - A*Q'
175 *
176       CALL DGEMM( 'No transpose''Transpose', M, N, N, -ONE, A, LDA, Q,
177      $            LDA, ONE, R, LDA )
178 *
179 *     Compute norm( R - A*Q' ) / ( MAX(M,N)*norm(A)*ULP ) .
180 *
181       RESID = DLANGE( '1', M, N, R, LDA, RWORK )
182       IF( ANORM.GT.ZERO ) THEN
183          RESULT1 ) = ( ( RESID / DBLEMAX1, M, N ) ) ) / ANORM ) /
184      $                 ULP
185       ELSE
186          RESULT1 ) = ZERO
187       END IF
188 *
189 *     Compute T*Q - Z'*B
190 *
191       CALL DGEMM( 'Transpose''No transpose', P, N, P, ONE, Z, LDB, B,
192      $            LDB, ZERO, BWK, LDB )
193       CALL DGEMM( 'No transpose''No transpose', P, N, N, ONE, T, LDB,
194      $            Q, LDA, -ONE, BWK, LDB )
195 *
196 *     Compute norm( T*Q - Z'*B ) / ( MAX(P,N)*norm(A)*ULP ) .
197 *
198       RESID = DLANGE( '1', P, N, BWK, LDB, RWORK )
199       IF( BNORM.GT.ZERO ) THEN
200          RESULT2 ) = ( ( RESID / DBLEMAX1, P, M ) ) ) / BNORM ) /
201      $                 ULP
202       ELSE
203          RESULT2 ) = ZERO
204       END IF
205 *
206 *     Compute I - Q*Q'
207 *
208       CALL DLASET( 'Full', N, N, ZERO, ONE, R, LDA )
209       CALL DSYRK( 'Upper''No Transpose', N, N, -ONE, Q, LDA, ONE, R,
210      $            LDA )
211 *
212 *     Compute norm( I - Q'*Q ) / ( N * ULP ) .
213 *
214       RESID = DLANSY( '1''Upper', N, R, LDA, RWORK )
215       RESULT3 ) = ( RESID / DBLEMAX1, N ) ) ) / ULP
216 *
217 *     Compute I - Z'*Z
218 *
219       CALL DLASET( 'Full', P, P, ZERO, ONE, T, LDB )
220       CALL DSYRK( 'Upper''Transpose', P, P, -ONE, Z, LDB, ONE, T,
221      $            LDB )
222 *
223 *     Compute norm( I - Z'*Z ) / ( P*ULP ) .
224 *
225       RESID = DLANSY( '1''Upper', P, T, LDB, RWORK )
226       RESULT4 ) = ( RESID / DBLEMAX1, P ) ) ) / ULP
227 *
228       RETURN
229 *
230 *     End of DGRQTS
231 *
232       END