1       SUBROUTINE CGQRTS( N, M, P, 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, P, N
 10 *     ..
 11 *     .. Array Arguments ..
 12       REAL               RWORK( * ), RESULT4 )
 13       COMPLEX            A( LDA, * ), AF( LDA, * ), R( LDA, * ),
 14      $                   Q( LDA, * ), B( LDB, * ), BF( LDB, * ),
 15      $                   T( LDB, * ), Z( LDB, * ), BWK( LDB, * ),
 16      $                   TAUA( * ), TAUB( * ), WORK( LWORK )
 17 *     ..
 18 *
 19 *  Purpose
 20 *  =======
 21 *
 22 *  CGQRTS tests CGGQRF, which computes the GQR factorization of an
 23 *  N-by-M matrix A and a N-by-P matrix B: A = Q*R and B = Q*T*Z.
 24 *
 25 *  Arguments
 26 *  =========
 27 *
 28 *  N       (input) INTEGER
 29 *          The number of rows of the matrices A and B.  N >= 0.
 30 *
 31 *  M       (input) INTEGER
 32 *          The number of columns of the matrix A.  M >= 0.
 33 *
 34 *  P       (input) INTEGER
 35 *          The number of columns of the matrix B.  P >= 0.
 36 *
 37 *  A       (input) COMPLEX array, dimension (LDA,M)
 38 *          The N-by-M matrix A.
 39 *
 40 *  AF      (output) COMPLEX array, dimension (LDA,N)
 41 *          Details of the GQR factorization of A and B, as returned
 42 *          by CGGQRF, see CGGQRF for further details.
 43 *
 44 *  Q       (output) COMPLEX array, dimension (LDA,N)
 45 *          The M-by-M unitary matrix Q.
 46 *
 47 *  R       (workspace) COMPLEX 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 array, dimension (min(M,N))
 54 *          The scalar factors of the elementary reflectors, as returned
 55 *          by CGGQRF.
 56 *
 57 *  B       (input) COMPLEX array, dimension (LDB,P)
 58 *          On entry, the N-by-P matrix A.
 59 *
 60 *  BF      (output) COMPLEX array, dimension (LDB,N)
 61 *          Details of the GQR factorization of A and B, as returned
 62 *          by CGGQRF, see CGGQRF for further details.
 63 *
 64 *  Z       (output) COMPLEX array, dimension (LDB,P)
 65 *          The P-by-P unitary matrix Z.
 66 *
 67 *  T       (workspace) COMPLEX array, dimension (LDB,max(P,N))
 68 *
 69 *  BWK     (workspace) COMPLEX 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 array, dimension (min(P,N))
 76 *          The scalar factors of the elementary reflectors, as returned
 77 *          by SGGRQF.
 78 *
 79 *  WORK    (workspace) COMPLEX array, dimension (LWORK)
 80 *
 81 *  LWORK   (input) INTEGER
 82 *          The dimension of the array WORK, LWORK >= max(N,M,P)**2.
 83 *
 84 *  RWORK   (workspace) REAL array, dimension (max(N,M,P))
 85 *
 86 *  RESULT  (output) REAL array, dimension (4)
 87 *          The test ratios:
 88 *            RESULT(1) = norm( R - Q'*A ) / ( MAX(M,N)*norm(A)*ULP)
 89 *            RESULT(2) = norm( T*Z - Q'*B ) / (MAX(P,N)*norm(B)*ULP)
 90 *            RESULT(3) = norm( I - Q'*Q ) / ( M*ULP )
 91 *            RESULT(4) = norm( I - Z'*Z ) / ( P*ULP )
 92 *
 93 *  =====================================================================
 94 *
 95 *     .. Parameters ..
 96       REAL               ZERO, ONE
 97       PARAMETER          ( ZERO = 0.0E+0, ONE = 1.0E+0 )
 98       COMPLEX            CZERO, CONE
 99       PARAMETER          ( CZERO = ( 0.0E+00.0E+0 ),
100      $                   CONE = ( 1.0E+00.0E+0 ) )
101       COMPLEX            CROGUE
102       PARAMETER          ( CROGUE = ( -1.0E+100.0E+0 ) )
103 *     ..
104 *     .. Local Scalars ..
105       INTEGER            INFO
106       REAL               ANORM, BNORM, ULP, UNFL, RESID
107 *     ..
108 *     .. External Functions ..
109       REAL               SLAMCH, CLANGE, CLANHE
110       EXTERNAL           SLAMCH, CLANGE, CLANHE
111 *     ..
112 *     .. External Subroutines ..
113       EXTERNAL           CGEMM, CLACPY, CLASET, CUNGQR,
114      $                   CUNGRQ, CHERK
115 *     ..
116 *     .. Intrinsic Functions ..
117       INTRINSIC          MAXMIN, REAL
118 *     ..
119 *     .. Executable Statements ..
120 *
121       ULP = SLAMCH( 'Precision' )
122       UNFL = SLAMCH( 'Safe minimum' )
123 *
124 *     Copy the matrix A to the array AF.
125 *
126       CALL CLACPY( 'Full', N, M, A, LDA, AF, LDA )
127       CALL CLACPY( 'Full', N, P, B, LDB, BF, LDB )
128 *
129       ANORM = MAX( CLANGE( '1', N, M, A, LDA, RWORK ), UNFL )
130       BNORM = MAX( CLANGE( '1', N, P, B, LDB, RWORK ), UNFL )
131 *
132 *     Factorize the matrices A and B in the arrays AF and BF.
133 *
134       CALL CGGQRF( N, M, P, AF, LDA, TAUA, BF, LDB, TAUB, WORK,
135      $             LWORK, INFO )
136 *
137 *     Generate the N-by-N matrix Q
138 *
139       CALL CLASET( 'Full', N, N, CROGUE, CROGUE, Q, LDA )
140       CALL CLACPY( 'Lower', N-1, M, AF( 2,1 ), LDA, Q( 2,1 ), LDA )
141       CALL CUNGQR( N, N, MIN( N, M ), Q, LDA, TAUA, WORK, LWORK, INFO )
142 *
143 *     Generate the P-by-P matrix Z
144 *
145       CALL CLASET( 'Full', P, P, CROGUE, CROGUE, Z, LDB )
146       IF( N.LE.P ) THEN
147          IF( N.GT.0 .AND. N.LT.P )
148      $      CALL CLACPY( 'Full', N, P-N, BF, LDB, Z( P-N+11 ), LDB )
149          IF( N.GT.1 )
150      $      CALL CLACPY( 'Lower', N-1, N-1, BF( 2, P-N+1 ), LDB,
151      $                    Z( P-N+2, P-N+1 ), LDB )
152       ELSE
153          IF( P.GT.1)
154      $      CALL CLACPY( 'Lower', P-1, P-1, BF( N-P+21 ), LDB,
155      $                    Z( 21 ), LDB )
156       END IF
157       CALL CUNGRQ( P, P, MIN( N, P ), Z, LDB, TAUB, WORK, LWORK, INFO )
158 *
159 *     Copy R
160 *
161       CALL CLASET( 'Full', N, M, CZERO, CZERO, R, LDA )
162       CALL CLACPY( 'Upper', N, M, AF, LDA, R, LDA )
163 *
164 *     Copy T
165 *
166       CALL CLASET( 'Full', N, P, CZERO, CZERO, T, LDB )
167       IF( N.LE.P ) THEN
168          CALL CLACPY( 'Upper', N, N, BF( 1, P-N+1 ), LDB, T( 1, P-N+1 ),
169      $                LDB )
170       ELSE
171          CALL CLACPY( 'Full', N-P, P, BF, LDB, T, LDB )
172          CALL CLACPY( 'Upper', P, P, BF( N-P+11 ), LDB, T( N-P+11 ),
173      $                LDB )
174       END IF
175 *
176 *     Compute R - Q'*A
177 *
178       CALL CGEMM( 'Conjugate transpose''No transpose', N, M, N, -CONE,
179      $            Q, LDA, A, LDA, CONE, R, LDA )
180 *
181 *     Compute norm( R - Q'*A ) / ( MAX(M,N)*norm(A)*ULP ) .
182 *
183       RESID = CLANGE( '1', N, M, R, LDA, RWORK )
184       IF( ANORM.GT.ZERO ) THEN
185          RESULT1 ) = ( ( RESID / REALMAX(1,M,N) ) ) / ANORM ) / ULP
186       ELSE
187          RESULT1 ) = ZERO
188       END IF
189 *
190 *     Compute T*Z - Q'*B
191 *
192       CALL CGEMM( 'No Transpose''No transpose', N, P, P, CONE, T, LDB,
193      $            Z, LDB, CZERO, BWK, LDB )
194       CALL CGEMM( 'Conjugate transpose''No transpose', N, P, N, -CONE,
195      $            Q, LDA, B, LDB, CONE, BWK, LDB )
196 *
197 *     Compute norm( T*Z - Q'*B ) / ( MAX(P,N)*norm(A)*ULP ) .
198 *
199       RESID = CLANGE( '1', N, P, BWK, LDB, RWORK )
200       IF( BNORM.GT.ZERO ) THEN
201          RESULT2 ) = ( ( RESID / REALMAX(1,P,N ) ) )/BNORM ) / ULP
202       ELSE
203          RESULT2 ) = ZERO
204       END IF
205 *
206 *     Compute I - Q'*Q
207 *
208       CALL CLASET( 'Full', N, N, CZERO, CONE, R, LDA )
209       CALL CHERK( 'Upper''Conjugate transpose', N, N, -ONE, Q, LDA,
210      $            ONE, R, LDA )
211 *
212 *     Compute norm( I - Q'*Q ) / ( N * ULP ) .
213 *
214       RESID = CLANHE( '1''Upper', N, R, LDA, RWORK )
215       RESULT3 ) = ( RESID / REALMAX1, N ) ) ) / ULP
216 *
217 *     Compute I - Z'*Z
218 *
219       CALL CLASET( 'Full', P, P, CZERO, CONE, T, LDB )
220       CALL CHERK( 'Upper''Conjugate transpose', P, P, -ONE, Z, LDB,
221      $            ONE, T, LDB )
222 *
223 *     Compute norm( I - Z'*Z ) / ( P*ULP ) .
224 *
225       RESID = CLANHE( '1''Upper', P, T, LDB, RWORK )
226       RESULT4 ) = ( RESID / REALMAX1, P ) ) ) / ULP
227 *
228       RETURN
229 *
230 *     End of CGQRTS
231 *
232       END