1       SUBROUTINE DGQRTS( 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, 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 *  DGQRTS tests DGGQRF, 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) DOUBLE PRECISION array, dimension (LDA,M)
 38 *          The N-by-M matrix A.
 39 *
 40 *  AF      (output) DOUBLE PRECISION array, dimension (LDA,N)
 41 *          Details of the GQR factorization of A and B, as returned
 42 *          by DGGQRF, see SGGQRF for further details.
 43 *
 44 *  Q       (output) DOUBLE PRECISION array, dimension (LDA,N)
 45 *          The M-by-M 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 DGGQRF.
 56 *
 57 *  B       (input) DOUBLE PRECISION array, dimension (LDB,P)
 58 *          On entry, the N-by-P 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 DGGQRF, see SGGQRF 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(N,M,P)**2.
 83 *
 84 *  RWORK   (workspace) DOUBLE PRECISION array, dimension (max(N,M,P))
 85 *
 86 *  RESULT  (output) DOUBLE PRECISION 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       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, DGGQRF, 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', N, M, A, LDA, AF, LDA )
124       CALL DLACPY( 'Full', N, P, B, LDB, BF, LDB )
125 *
126       ANORM = MAX( DLANGE( '1', N, M, A, LDA, RWORK ), UNFL )
127       BNORM = MAX( DLANGE( '1', N, P, B, LDB, RWORK ), UNFL )
128 *
129 *     Factorize the matrices A and B in the arrays AF and BF.
130 *
131       CALL DGGQRF( N, M, P, 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       CALL DLACPY( 'Lower', N-1, M, AF( 21 ), LDA, Q( 21 ), LDA )
138       CALL DORGQR( N, N, MIN( N, M ), Q, LDA, TAUA, WORK, LWORK, INFO )
139 *
140 *     Generate the P-by-P matrix Z
141 *
142       CALL DLASET( 'Full', P, P, ROGUE, ROGUE, Z, LDB )
143       IF( N.LE.P ) THEN
144          IF( N.GT.0 .AND. N.LT.P )
145      $      CALL DLACPY( 'Full', N, P-N, BF, LDB, Z( P-N+11 ), LDB )
146          IF( N.GT.1 )
147      $      CALL DLACPY( 'Lower', N-1, N-1, BF( 2, P-N+1 ), LDB,
148      $                   Z( P-N+2, P-N+1 ), LDB )
149       ELSE
150          IF( P.GT.1 )
151      $      CALL DLACPY( 'Lower', P-1, P-1, BF( N-P+21 ), LDB,
152      $                   Z( 21 ), LDB )
153       END IF
154       CALL DORGRQ( P, P, MIN( N, P ), Z, LDB, TAUB, WORK, LWORK, INFO )
155 *
156 *     Copy R
157 *
158       CALL DLASET( 'Full', N, M, ZERO, ZERO, R, LDA )
159       CALL DLACPY( 'Upper', N, M, AF, LDA, R, LDA )
160 *
161 *     Copy T
162 *
163       CALL DLASET( 'Full', N, P, ZERO, ZERO, T, LDB )
164       IF( N.LE.P ) THEN
165          CALL DLACPY( 'Upper', N, N, BF( 1, P-N+1 ), LDB, T( 1, P-N+1 ),
166      $                LDB )
167       ELSE
168          CALL DLACPY( 'Full', N-P, P, BF, LDB, T, LDB )
169          CALL DLACPY( 'Upper', P, P, BF( N-P+11 ), LDB, T( N-P+11 ),
170      $                LDB )
171       END IF
172 *
173 *     Compute R - Q'*A
174 *
175       CALL DGEMM( 'Transpose''No transpose', N, M, N, -ONE, Q, LDA, A,
176      $            LDA, ONE, R, LDA )
177 *
178 *     Compute norm( R - Q'*A ) / ( MAX(M,N)*norm(A)*ULP ) .
179 *
180       RESID = DLANGE( '1', N, M, R, LDA, RWORK )
181       IF( ANORM.GT.ZERO ) THEN
182          RESULT1 ) = ( ( RESID / DBLEMAX1, M, N ) ) ) / ANORM ) /
183      $                 ULP
184       ELSE
185          RESULT1 ) = ZERO
186       END IF
187 *
188 *     Compute T*Z - Q'*B
189 *
190       CALL DGEMM( 'No Transpose''No transpose', N, P, P, ONE, T, LDB,
191      $            Z, LDB, ZERO, BWK, LDB )
192       CALL DGEMM( 'Transpose''No transpose', N, P, N, -ONE, Q, LDA, B,
193      $            LDB, ONE, BWK, LDB )
194 *
195 *     Compute norm( T*Z - Q'*B ) / ( MAX(P,N)*norm(A)*ULP ) .
196 *
197       RESID = DLANGE( '1', N, P, BWK, LDB, RWORK )
198       IF( BNORM.GT.ZERO ) THEN
199          RESULT2 ) = ( ( RESID / DBLEMAX1, P, N ) ) ) / BNORM ) /
200      $                 ULP
201       ELSE
202          RESULT2 ) = ZERO
203       END IF
204 *
205 *     Compute I - Q'*Q
206 *
207       CALL DLASET( 'Full', N, N, ZERO, ONE, R, LDA )
208       CALL DSYRK( 'Upper''Transpose', N, N, -ONE, Q, LDA, ONE, R,
209      $            LDA )
210 *
211 *     Compute norm( I - Q'*Q ) / ( N * ULP ) .
212 *
213       RESID = DLANSY( '1''Upper', N, R, LDA, RWORK )
214       RESULT3 ) = ( RESID / DBLEMAX1, N ) ) ) / ULP
215 *
216 *     Compute I - Z'*Z
217 *
218       CALL DLASET( 'Full', P, P, ZERO, ONE, T, LDB )
219       CALL DSYRK( 'Upper''Transpose', P, P, -ONE, Z, LDB, ONE, T,
220      $            LDB )
221 *
222 *     Compute norm( I - Z'*Z ) / ( P*ULP ) .
223 *
224       RESID = DLANSY( '1''Upper', P, T, LDB, RWORK )
225       RESULT4 ) = ( RESID / DBLEMAX1, P ) ) ) / ULP
226 *
227       RETURN
228 *
229 *     End of DGQRTS
230 *
231       END