1       SUBROUTINE SGRQTS( 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, P, N
 10 *     ..
 11 *     .. Array Arguments ..
 12       REAL               A( LDA, * ), AF( LDA, * ), R( LDA, * ),
 13      $                   Q( LDA, * ),
 14      $                   B( LDB, * ), BF( LDB, * ), T( LDB, * ),
 15      $                   Z( LDB, * ), BWK( LDB, * ),
 16      $                   TAUA( * ), TAUB( * ),
 17      $                   RESULT4 ), RWORK( * ), WORK( LWORK )
 18 *     ..
 19 *
 20 *  Purpose
 21 *  =======
 22 *
 23 *  SGRQTS tests SGGRQF, which computes the GRQ factorization of an
 24 *  M-by-N matrix A and a P-by-N matrix B: A = R*Q and B = Z*T*Q.
 25 *
 26 *  Arguments
 27 *  =========
 28 *
 29 *  M       (input) INTEGER
 30 *          The number of rows of the matrix A.  M >= 0.
 31 *
 32 *  P       (input) INTEGER
 33 *          The number of rows of the matrix B.  P >= 0.
 34 *
 35 *  N       (input) INTEGER
 36 *          The number of columns of the matrices A and B.  N >= 0.
 37 *
 38 *  A       (input) REAL array, dimension (LDA,N)
 39 *          The M-by-N matrix A.
 40 *
 41 *  AF      (output) REAL array, dimension (LDA,N)
 42 *          Details of the GRQ factorization of A and B, as returned
 43 *          by SGGRQF, see SGGRQF for further details.
 44 *
 45 *  Q       (output) REAL array, dimension (LDA,N)
 46 *          The N-by-N orthogonal matrix Q.
 47 *
 48 *  R       (workspace) REAL array, dimension (LDA,MAX(M,N))
 49 *
 50 *  LDA     (input) INTEGER
 51 *          The leading dimension of the arrays A, AF, R and Q.
 52 *          LDA >= max(M,N).
 53 *
 54 *  TAUA    (output) REAL array, dimension (min(M,N))
 55 *          The scalar factors of the elementary reflectors, as returned
 56 *          by SGGQRC.
 57 *
 58 *  B       (input) REAL array, dimension (LDB,N)
 59 *          On entry, the P-by-N matrix A.
 60 *
 61 *  BF      (output) REAL array, dimension (LDB,N)
 62 *          Details of the GQR factorization of A and B, as returned
 63 *          by SGGRQF, see SGGRQF for further details.
 64 *
 65 *  Z       (output) REAL array, dimension (LDB,P)
 66 *          The P-by-P orthogonal matrix Z.
 67 *
 68 *  T       (workspace) REAL array, dimension (LDB,max(P,N))
 69 *
 70 *  BWK     (workspace) REAL array, dimension (LDB,N)
 71 *
 72 *  LDB     (input) INTEGER
 73 *          The leading dimension of the arrays B, BF, Z and T.
 74 *          LDB >= max(P,N).
 75 *
 76 *  TAUB    (output) REAL array, dimension (min(P,N))
 77 *          The scalar factors of the elementary reflectors, as returned
 78 *          by SGGRQF.
 79 *
 80 *  WORK    (workspace) REAL array, dimension (LWORK)
 81 *
 82 *  LWORK   (input) INTEGER
 83 *          The dimension of the array WORK, LWORK >= max(M,P,N)**2.
 84 *
 85 *  RWORK   (workspace) REAL array, dimension (M)
 86 *
 87 *  RESULT  (output) REAL array, dimension (4)
 88 *          The test ratios:
 89 *            RESULT(1) = norm( R - A*Q' ) / ( MAX(M,N)*norm(A)*ULP)
 90 *            RESULT(2) = norm( T*Q - Z'*B ) / (MAX(P,N)*norm(B)*ULP)
 91 *            RESULT(3) = norm( I - Q'*Q ) / ( N*ULP )
 92 *            RESULT(4) = norm( I - Z'*Z ) / ( P*ULP )
 93 *
 94 *  =====================================================================
 95 *
 96 *     .. Parameters ..
 97       REAL               ZERO, ONE
 98       PARAMETER          ( ZERO = 0.0E+0, ONE = 1.0E+0 )
 99       REAL               ROGUE
100       PARAMETER          ( ROGUE = -1.0E+10 )
101 *     ..
102 *     .. Local Scalars ..
103       INTEGER            INFO
104       REAL               ANORM, BNORM, ULP, UNFL, RESID
105 *     ..
106 *     .. External Functions ..
107       REAL               SLAMCH, SLANGE, SLANSY
108       EXTERNAL           SLAMCH, SLANGE, SLANSY
109 *     ..
110 *     .. External Subroutines ..
111       EXTERNAL           SGEMM, SGGRQF, SLACPY, SLASET, SORGQR,
112      $                   SORGRQ, SSYRK
113 *     ..
114 *     .. Intrinsic Functions ..
115       INTRINSIC          MAXMIN, REAL
116 *     ..
117 *     .. Executable Statements ..
118 *
119       ULP = SLAMCH( 'Precision' )
120       UNFL = SLAMCH( 'Safe minimum' )
121 *
122 *     Copy the matrix A to the array AF.
123 *
124       CALL SLACPY( 'Full', M, N, A, LDA, AF, LDA )
125       CALL SLACPY( 'Full', P, N, B, LDB, BF, LDB )
126 *
127       ANORM = MAX( SLANGE( '1', M, N, A, LDA, RWORK ), UNFL )
128       BNORM = MAX( SLANGE( '1', P, N, B, LDB, RWORK ), UNFL )
129 *
130 *     Factorize the matrices A and B in the arrays AF and BF.
131 *
132       CALL SGGRQF( M, P, N, AF, LDA, TAUA, BF, LDB, TAUB, WORK,
133      $             LWORK, INFO )
134 *
135 *     Generate the N-by-N matrix Q
136 *
137       CALL SLASET( 'Full', N, N, ROGUE, ROGUE, Q, LDA )
138       IF( M.LE.N ) THEN
139          IF( M.GT.0 .AND. M.LT.N )
140      $      CALL SLACPY( 'Full', M, N-M, AF, LDA, Q( N-M+11 ), LDA )
141          IF( M.GT.1 )
142      $      CALL SLACPY( 'Lower', M-1, M-1, AF( 2, N-M+1 ), LDA,
143      $                   Q( N-M+2, N-M+1 ), LDA )
144       ELSE
145          IF( N.GT.1 )
146      $      CALL SLACPY( 'Lower', N-1, N-1, AF( M-N+21 ), LDA,
147      $                   Q( 21 ), LDA )
148       END IF
149       CALL SORGRQ( N, N, MIN( M, N ), Q, LDA, TAUA, WORK, LWORK, INFO )
150 *
151 *     Generate the P-by-P matrix Z
152 *
153       CALL SLASET( 'Full', P, P, ROGUE, ROGUE, Z, LDB )
154       IF( P.GT.1 )
155      $   CALL SLACPY( 'Lower', P-1, N, BF( 2,1 ), LDB, Z( 2,1 ), LDB )
156       CALL SORGQR( P, P, MIN( P,N ), Z, LDB, TAUB, WORK, LWORK, INFO )
157 *
158 *     Copy R
159 *
160       CALL SLASET( 'Full', M, N, ZERO, ZERO, R, LDA )
161       IF( M.LE.N )THEN
162          CALL SLACPY( 'Upper', M, M, AF( 1, N-M+1 ), LDA, R( 1, N-M+1 ),
163      $                LDA )
164       ELSE
165          CALL SLACPY( 'Full', M-N, N, AF, LDA, R, LDA )
166          CALL SLACPY( 'Upper', N, N, AF( M-N+11 ), LDA, R( M-N+11 ),
167      $                LDA )
168       END IF
169 *
170 *     Copy T
171 *
172       CALL SLASET( 'Full', P, N, ZERO, ZERO, T, LDB )
173       CALL SLACPY( 'Upper', P, N, BF, LDB, T, LDB )
174 *
175 *     Compute R - A*Q'
176 *
177       CALL SGEMM( 'No transpose''Transpose', M, N, N, -ONE, A, LDA, Q,
178      $            LDA, ONE, R, LDA )
179 *
180 *     Compute norm( R - A*Q' ) / ( MAX(M,N)*norm(A)*ULP ) .
181 *
182       RESID = SLANGE( '1', M, N, R, LDA, RWORK )
183       IF( ANORM.GT.ZERO ) THEN
184          RESULT1 ) = ( ( RESID / REAL(MAX(1,M,N) ) ) / ANORM ) / ULP
185       ELSE
186          RESULT1 ) = ZERO
187       END IF
188 *
189 *     Compute T*Q - Z'*B
190 *
191       CALL SGEMM( 'Transpose''No transpose', P, N, P, ONE, Z, LDB, B,
192      $            LDB, ZERO, BWK, LDB )
193       CALL SGEMM( '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 = SLANGE( '1', P, N, BWK, LDB, RWORK )
199       IF( BNORM.GT.ZERO ) THEN
200          RESULT2 ) = ( ( RESID / REALMAX1,P,M ) ) )/BNORM ) / ULP
201       ELSE
202          RESULT2 ) = ZERO
203       END IF
204 *
205 *     Compute I - Q*Q'
206 *
207       CALL SLASET( 'Full', N, N, ZERO, ONE, R, LDA )
208       CALL SSYRK( 'Upper''No Transpose', N, N, -ONE, Q, LDA, ONE, R,
209      $            LDA )
210 *
211 *     Compute norm( I - Q'*Q ) / ( N * ULP ) .
212 *
213       RESID = SLANSY( '1''Upper', N, R, LDA, RWORK )
214       RESULT3 ) = ( RESID / REALMAX1,N ) ) ) / ULP
215 *
216 *     Compute I - Z'*Z
217 *
218       CALL SLASET( 'Full', P, P, ZERO, ONE, T, LDB )
219       CALL SSYRK( 'Upper''Transpose', P, P, -ONE, Z, LDB, ONE, T,
220      $            LDB )
221 *
222 *     Compute norm( I - Z'*Z ) / ( P*ULP ) .
223 *
224       RESID = SLANSY( '1''Upper', P, T, LDB, RWORK )
225       RESULT4 ) = ( RESID / REALMAX1,P ) ) ) / ULP
226 *
227       RETURN
228 *
229 *     End of SGRQTS
230 *
231       END