1       SUBROUTINE DQRT15( SCALE, RKSEL, M, N, NRHS, A, LDA, B, LDB, S,
  2      $                   RANK, NORMA, NORMB, ISEED, WORK, LWORK )
  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, NRHS, RANK, RKSEL, SCALE
 10       DOUBLE PRECISION   NORMA, NORMB
 11 *     ..
 12 *     .. Array Arguments ..
 13       INTEGER            ISEED( 4 )
 14       DOUBLE PRECISION   A( LDA, * ), B( LDB, * ), S( * ), WORK( LWORK )
 15 *     ..
 16 *
 17 *  Purpose
 18 *  =======
 19 *
 20 *  DQRT15 generates a matrix with full or deficient rank and of various
 21 *  norms.
 22 *
 23 *  Arguments
 24 *  =========
 25 *
 26 *  SCALE   (input) INTEGER
 27 *          SCALE = 1: normally scaled matrix
 28 *          SCALE = 2: matrix scaled up
 29 *          SCALE = 3: matrix scaled down
 30 *
 31 *  RKSEL   (input) INTEGER
 32 *          RKSEL = 1: full rank matrix
 33 *          RKSEL = 2: rank-deficient matrix
 34 *
 35 *  M       (input) INTEGER
 36 *          The number of rows of the matrix A.
 37 *
 38 *  N       (input) INTEGER
 39 *          The number of columns of A.
 40 *
 41 *  NRHS    (input) INTEGER
 42 *          The number of columns of B.
 43 *
 44 *  A       (output) DOUBLE PRECISION array, dimension (LDA,N)
 45 *          The M-by-N matrix A.
 46 *
 47 *  LDA     (input) INTEGER
 48 *          The leading dimension of the array A.
 49 *
 50 *  B       (output) DOUBLE PRECISION array, dimension (LDB, NRHS)
 51 *          A matrix that is in the range space of matrix A.
 52 *
 53 *  LDB     (input) INTEGER
 54 *          The leading dimension of the array B.
 55 *
 56 *  S       (output) DOUBLE PRECISION array, dimension MIN(M,N)
 57 *          Singular values of A.
 58 *
 59 *  RANK    (output) INTEGER
 60 *          number of nonzero singular values of A.
 61 *
 62 *  NORMA   (output) DOUBLE PRECISION
 63 *          one-norm of A.
 64 *
 65 *  NORMB   (output) DOUBLE PRECISION
 66 *          one-norm of B.
 67 *
 68 *  ISEED   (input/output) integer array, dimension (4)
 69 *          seed for random number generator.
 70 *
 71 *  WORK    (workspace) DOUBLE PRECISION array, dimension (LWORK)
 72 *
 73 *  LWORK   (input) INTEGER
 74 *          length of work space required.
 75 *          LWORK >= MAX(M+MIN(M,N),NRHS*MIN(M,N),2*N+M)
 76 *
 77 *  =====================================================================
 78 *
 79 *     .. Parameters ..
 80       DOUBLE PRECISION   ZERO, ONE, TWO, SVMIN
 81       PARAMETER          ( ZERO = 0.0D0, ONE = 1.0D0, TWO = 2.0D0,
 82      $                   SVMIN = 0.1D0 )
 83 *     ..
 84 *     .. Local Scalars ..
 85       INTEGER            INFO, J, MN
 86       DOUBLE PRECISION   BIGNUM, EPS, SMLNUM, TEMP
 87 *     ..
 88 *     .. Local Arrays ..
 89       DOUBLE PRECISION   DUMMY( 1 )
 90 *     ..
 91 *     .. External Functions ..
 92       DOUBLE PRECISION   DASUM, DLAMCH, DLANGE, DLARND, DNRM2
 93       EXTERNAL           DASUM, DLAMCH, DLANGE, DLARND, DNRM2
 94 *     ..
 95 *     .. External Subroutines ..
 96       EXTERNAL           DGEMM, DLAORD, DLARF, DLARNV, DLAROR, DLASCL,
 97      $                   DLASET, DSCAL, XERBLA
 98 *     ..
 99 *     .. Intrinsic Functions ..
100       INTRINSIC          ABSMAXMIN
101 *     ..
102 *     .. Executable Statements ..
103 *
104       MN = MIN( M, N )
105       IF( LWORK.LT.MAX( M+MN, MN*NRHS, 2*N+M ) ) THEN
106          CALL XERBLA( 'DQRT15'16 )
107          RETURN
108       END IF
109 *
110       SMLNUM = DLAMCH( 'Safe minimum' )
111       BIGNUM = ONE / SMLNUM
112       EPS = DLAMCH( 'Epsilon' )
113       SMLNUM = ( SMLNUM / EPS ) / EPS
114       BIGNUM = ONE / SMLNUM
115 *
116 *     Determine rank and (unscaled) singular values
117 *
118       IF( RKSEL.EQ.1 ) THEN
119          RANK = MN
120       ELSE IF( RKSEL.EQ.2 ) THEN
121          RANK = ( 3*MN ) / 4
122          DO 10 J = RANK + 1, MN
123             S( J ) = ZERO
124    10    CONTINUE
125       ELSE
126          CALL XERBLA( 'DQRT15'2 )
127       END IF
128 *
129       IF( RANK.GT.0 ) THEN
130 *
131 *        Nontrivial case
132 *
133          S( 1 ) = ONE
134          DO 30 J = 2, RANK
135    20       CONTINUE
136             TEMP = DLARND( 1, ISEED )
137             IF( TEMP.GT.SVMIN ) THEN
138                S( J ) = ABS( TEMP )
139             ELSE
140                GO TO 20
141             END IF
142    30    CONTINUE
143          CALL DLAORD( 'Decreasing', RANK, S, 1 )
144 *
145 *        Generate 'rank' columns of a random orthogonal matrix in A
146 *
147          CALL DLARNV( 2, ISEED, M, WORK )
148          CALL DSCAL( M, ONE / DNRM2( M, WORK, 1 ), WORK, 1 )
149          CALL DLASET( 'Full', M, RANK, ZERO, ONE, A, LDA )
150          CALL DLARF( 'Left', M, RANK, WORK, 1, TWO, A, LDA,
151      $               WORK( M+1 ) )
152 *
153 *        workspace used: m+mn
154 *
155 *        Generate consistent rhs in the range space of A
156 *
157          CALL DLARNV( 2, ISEED, RANK*NRHS, WORK )
158          CALL DGEMM( 'No transpose''No transpose', M, NRHS, RANK, ONE,
159      $               A, LDA, WORK, RANK, ZERO, B, LDB )
160 *
161 *        work space used: <= mn *nrhs
162 *
163 *        generate (unscaled) matrix A
164 *
165          DO 40 J = 1, RANK
166             CALL DSCAL( M, S( J ), A( 1, J ), 1 )
167    40    CONTINUE
168          IF( RANK.LT.N )
169      $      CALL DLASET( 'Full', M, N-RANK, ZERO, ZERO, A( 1, RANK+1 ),
170      $                   LDA )
171          CALL DLAROR( 'Right''No initialization', M, N, A, LDA, ISEED,
172      $                WORK, INFO )
173 *
174       ELSE
175 *
176 *        work space used 2*n+m
177 *
178 *        Generate null matrix and rhs
179 *
180          DO 50 J = 1, MN
181             S( J ) = ZERO
182    50    CONTINUE
183          CALL DLASET( 'Full', M, N, ZERO, ZERO, A, LDA )
184          CALL DLASET( 'Full', M, NRHS, ZERO, ZERO, B, LDB )
185 *
186       END IF
187 *
188 *     Scale the matrix
189 *
190       IFSCALE.NE.1 ) THEN
191          NORMA = DLANGE( 'Max', M, N, A, LDA, DUMMY )
192          IF( NORMA.NE.ZERO ) THEN
193             IFSCALE.EQ.2 ) THEN
194 *
195 *              matrix scaled up
196 *
197                CALL DLASCL( 'General'00, NORMA, BIGNUM, M, N, A,
198      $                      LDA, INFO )
199                CALL DLASCL( 'General'00, NORMA, BIGNUM, MN, 1, S,
200      $                      MN, INFO )
201                CALL DLASCL( 'General'00, NORMA, BIGNUM, M, NRHS, B,
202      $                      LDB, INFO )
203             ELSE IFSCALE.EQ.3 ) THEN
204 *
205 *              matrix scaled down
206 *
207                CALL DLASCL( 'General'00, NORMA, SMLNUM, M, N, A,
208      $                      LDA, INFO )
209                CALL DLASCL( 'General'00, NORMA, SMLNUM, MN, 1, S,
210      $                      MN, INFO )
211                CALL DLASCL( 'General'00, NORMA, SMLNUM, M, NRHS, B,
212      $                      LDB, INFO )
213             ELSE
214                CALL XERBLA( 'DQRT15'1 )
215                RETURN
216             END IF
217          END IF
218       END IF
219 *
220       NORMA = DASUM( MN, S, 1 )
221       NORMB = DLANGE( 'One-norm', M, NRHS, B, LDB, DUMMY )
222 *
223       RETURN
224 *
225 *     End of DQRT15
226 *
227       END