1       SUBROUTINE ZGRQTS( 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   RESULT4 ), RWORK( * )
 13       COMPLEX*16         A( LDA, * ), AF( LDA, * ), B( LDB, * ),
 14      $                   BF( LDB, * ), BWK( LDB, * ), Q( LDA, * ),
 15      $                   R( LDA, * ), T( LDB, * ), TAUA( * ), TAUB( * ),
 16      $                   WORK( LWORK ), Z( LDB, * )
 17 *     ..
 18 *
 19 *  Purpose
 20 *  =======
 21 *
 22 *  ZGRQTS tests ZGGRQF, 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) COMPLEX*16 array, dimension (LDA,N)
 38 *          The M-by-N matrix A.
 39 *
 40 *  AF      (output) COMPLEX*16 array, dimension (LDA,N)
 41 *          Details of the GRQ factorization of A and B, as returned
 42 *          by ZGGRQF, see CGGRQF for further details.
 43 *
 44 *  Q       (output) COMPLEX*16 array, dimension (LDA,N)
 45 *          The N-by-N unitary matrix Q.
 46 *
 47 *  R       (workspace) COMPLEX*16 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) COMPLEX*16 array, dimension (min(M,N))
 54 *          The scalar factors of the elementary reflectors, as returned
 55 *          by DGGQRC.
 56 *
 57 *  B       (input) COMPLEX*16 array, dimension (LDB,N)
 58 *          On entry, the P-by-N matrix A.
 59 *
 60 *  BF      (output) COMPLEX*16 array, dimension (LDB,N)
 61 *          Details of the GQR factorization of A and B, as returned
 62 *          by ZGGRQF, see CGGRQF for further details.
 63 *
 64 *  Z       (output) DOUBLE PRECISION array, dimension (LDB,P)
 65 *          The P-by-P unitary matrix Z.
 66 *
 67 *  T       (workspace) COMPLEX*16 array, dimension (LDB,max(P,N))
 68 *
 69 *  BWK     (workspace) COMPLEX*16 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) COMPLEX*16 array, dimension (min(P,N))
 76 *          The scalar factors of the elementary reflectors, as returned
 77 *          by DGGRQF.
 78 *
 79 *  WORK    (workspace) COMPLEX*16 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       COMPLEX*16         CZERO, CONE
 99       PARAMETER          ( CZERO = ( 0.0D+00.0D+0 ),
100      $                   CONE = ( 1.0D+00.0D+0 ) )
101       COMPLEX*16         CROGUE
102       PARAMETER          ( CROGUE = ( -1.0D+100.0D+0 ) )
103 *     ..
104 *     .. Local Scalars ..
105       INTEGER            INFO
106       DOUBLE PRECISION   ANORM, BNORM, RESID, ULP, UNFL
107 *     ..
108 *     .. External Functions ..
109       DOUBLE PRECISION   DLAMCH, ZLANGE, ZLANHE
110       EXTERNAL           DLAMCH, ZLANGE, ZLANHE
111 *     ..
112 *     .. External Subroutines ..
113       EXTERNAL           ZGEMM, ZGGRQF, ZHERK, ZLACPY, ZLASET, ZUNGQR,
114      $                   ZUNGRQ
115 *     ..
116 *     .. Intrinsic Functions ..
117       INTRINSIC          DBLEMAXMIN
118 *     ..
119 *     .. Executable Statements ..
120 *
121       ULP = DLAMCH( 'Precision' )
122       UNFL = DLAMCH( 'Safe minimum' )
123 *
124 *     Copy the matrix A to the array AF.
125 *
126       CALL ZLACPY( 'Full', M, N, A, LDA, AF, LDA )
127       CALL ZLACPY( 'Full', P, N, B, LDB, BF, LDB )
128 *
129       ANORM = MAX( ZLANGE( '1', M, N, A, LDA, RWORK ), UNFL )
130       BNORM = MAX( ZLANGE( '1', P, N, B, LDB, RWORK ), UNFL )
131 *
132 *     Factorize the matrices A and B in the arrays AF and BF.
133 *
134       CALL ZGGRQF( M, P, N, AF, LDA, TAUA, BF, LDB, TAUB, WORK, LWORK,
135      $             INFO )
136 *
137 *     Generate the N-by-N matrix Q
138 *
139       CALL ZLASET( 'Full', N, N, CROGUE, CROGUE, Q, LDA )
140       IF( M.LE.N ) THEN
141          IF( M.GT.0 .AND. M.LT.N )
142      $      CALL ZLACPY( 'Full', M, N-M, AF, LDA, Q( N-M+11 ), LDA )
143          IF( M.GT.1 )
144      $      CALL ZLACPY( 'Lower', M-1, M-1, AF( 2, N-M+1 ), LDA,
145      $                   Q( N-M+2, N-M+1 ), LDA )
146       ELSE
147          IF( N.GT.1 )
148      $      CALL ZLACPY( 'Lower', N-1, N-1, AF( M-N+21 ), LDA,
149      $                   Q( 21 ), LDA )
150       END IF
151       CALL ZUNGRQ( N, N, MIN( M, N ), Q, LDA, TAUA, WORK, LWORK, INFO )
152 *
153 *     Generate the P-by-P matrix Z
154 *
155       CALL ZLASET( 'Full', P, P, CROGUE, CROGUE, Z, LDB )
156       IF( P.GT.1 )
157      $   CALL ZLACPY( 'Lower', P-1, N, BF( 21 ), LDB, Z( 21 ), LDB )
158       CALL ZUNGQR( P, P, MIN( P, N ), Z, LDB, TAUB, WORK, LWORK, INFO )
159 *
160 *     Copy R
161 *
162       CALL ZLASET( 'Full', M, N, CZERO, CZERO, R, LDA )
163       IF( M.LE.N ) THEN
164          CALL ZLACPY( 'Upper', M, M, AF( 1, N-M+1 ), LDA, R( 1, N-M+1 ),
165      $                LDA )
166       ELSE
167          CALL ZLACPY( 'Full', M-N, N, AF, LDA, R, LDA )
168          CALL ZLACPY( 'Upper', N, N, AF( M-N+11 ), LDA, R( M-N+11 ),
169      $                LDA )
170       END IF
171 *
172 *     Copy T
173 *
174       CALL ZLASET( 'Full', P, N, CZERO, CZERO, T, LDB )
175       CALL ZLACPY( 'Upper', P, N, BF, LDB, T, LDB )
176 *
177 *     Compute R - A*Q'
178 *
179       CALL ZGEMM( 'No transpose''Conjugate transpose', M, N, N, -CONE,
180      $            A, LDA, Q, LDA, CONE, R, LDA )
181 *
182 *     Compute norm( R - A*Q' ) / ( MAX(M,N)*norm(A)*ULP ) .
183 *
184       RESID = ZLANGE( '1', M, N, R, LDA, RWORK )
185       IF( ANORM.GT.ZERO ) THEN
186          RESULT1 ) = ( ( RESID / DBLEMAX1, M, N ) ) ) / ANORM ) /
187      $                 ULP
188       ELSE
189          RESULT1 ) = ZERO
190       END IF
191 *
192 *     Compute T*Q - Z'*B
193 *
194       CALL ZGEMM( 'Conjugate transpose''No transpose', P, N, P, CONE,
195      $            Z, LDB, B, LDB, CZERO, BWK, LDB )
196       CALL ZGEMM( 'No transpose''No transpose', P, N, N, CONE, T, LDB,
197      $            Q, LDA, -CONE, BWK, LDB )
198 *
199 *     Compute norm( T*Q - Z'*B ) / ( MAX(P,N)*norm(A)*ULP ) .
200 *
201       RESID = ZLANGE( '1', P, N, BWK, LDB, RWORK )
202       IF( BNORM.GT.ZERO ) THEN
203          RESULT2 ) = ( ( RESID / DBLEMAX1, P, M ) ) ) / BNORM ) /
204      $                 ULP
205       ELSE
206          RESULT2 ) = ZERO
207       END IF
208 *
209 *     Compute I - Q*Q'
210 *
211       CALL ZLASET( 'Full', N, N, CZERO, CONE, R, LDA )
212       CALL ZHERK( 'Upper''No Transpose', N, N, -ONE, Q, LDA, ONE, R,
213      $            LDA )
214 *
215 *     Compute norm( I - Q'*Q ) / ( N * ULP ) .
216 *
217       RESID = ZLANHE( '1''Upper', N, R, LDA, RWORK )
218       RESULT3 ) = ( RESID / DBLEMAX1, N ) ) ) / ULP
219 *
220 *     Compute I - Z'*Z
221 *
222       CALL ZLASET( 'Full', P, P, CZERO, CONE, T, LDB )
223       CALL ZHERK( 'Upper''Conjugate transpose', P, P, -ONE, Z, LDB,
224      $            ONE, T, LDB )
225 *
226 *     Compute norm( I - Z'*Z ) / ( P*ULP ) .
227 *
228       RESID = ZLANHE( '1''Upper', P, T, LDB, RWORK )
229       RESULT4 ) = ( RESID / DBLEMAX1, P ) ) ) / ULP
230 *
231       RETURN
232 *
233 *     End of ZGRQTS
234 *
235       END