1       SUBROUTINE CQLT01( M, N, A, AF, Q, L, LDA, TAU, WORK, LWORK,
  2      $                   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, LWORK, M, N
 10 *     ..
 11 *     .. Array Arguments ..
 12       REAL               RESULT* ), RWORK( * )
 13       COMPLEX            A( LDA, * ), AF( LDA, * ), L( LDA, * ),
 14      $                   Q( LDA, * ), TAU( * ), WORK( LWORK )
 15 *     ..
 16 *
 17 *  Purpose
 18 *  =======
 19 *
 20 *  CQLT01 tests CGEQLF, which computes the QL factorization of an m-by-n
 21 *  matrix A, and partially tests CUNGQL which forms the m-by-m
 22 *  orthogonal matrix Q.
 23 *
 24 *  CQLT01 compares L with Q'*A, and checks that Q is orthogonal.
 25 *
 26 *  Arguments
 27 *  =========
 28 *
 29 *  M       (input) INTEGER
 30 *          The number of rows of the matrix A.  M >= 0.
 31 *
 32 *  N       (input) INTEGER
 33 *          The number of columns of the matrix A.  N >= 0.
 34 *
 35 *  A       (input) COMPLEX array, dimension (LDA,N)
 36 *          The m-by-n matrix A.
 37 *
 38 *  AF      (output) COMPLEX array, dimension (LDA,N)
 39 *          Details of the QL factorization of A, as returned by CGEQLF.
 40 *          See CGEQLF for further details.
 41 *
 42 *  Q       (output) COMPLEX array, dimension (LDA,M)
 43 *          The m-by-m orthogonal matrix Q.
 44 *
 45 *  L       (workspace) COMPLEX array, dimension (LDA,max(M,N))
 46 *
 47 *  LDA     (input) INTEGER
 48 *          The leading dimension of the arrays A, AF, Q and R.
 49 *          LDA >= max(M,N).
 50 *
 51 *  TAU     (output) COMPLEX array, dimension (min(M,N))
 52 *          The scalar factors of the elementary reflectors, as returned
 53 *          by CGEQLF.
 54 *
 55 *  WORK    (workspace) COMPLEX array, dimension (LWORK)
 56 *
 57 *  LWORK   (input) INTEGER
 58 *          The dimension of the array WORK.
 59 *
 60 *  RWORK   (workspace) REAL array, dimension (M)
 61 *
 62 *  RESULT  (output) REAL array, dimension (2)
 63 *          The test ratios:
 64 *          RESULT(1) = norm( L - Q'*A ) / ( M * norm(A) * EPS )
 65 *          RESULT(2) = norm( I - Q'*Q ) / ( M * EPS )
 66 *
 67 *  =====================================================================
 68 *
 69 *     .. Parameters ..
 70       REAL               ZERO, ONE
 71       PARAMETER          ( ZERO = 0.0E+0, ONE = 1.0E+0 )
 72       COMPLEX            ROGUE
 73       PARAMETER          ( ROGUE = ( -1.0E+10-1.0E+10 ) )
 74 *     ..
 75 *     .. Local Scalars ..
 76       INTEGER            INFO, MINMN
 77       REAL               ANORM, EPS, RESID
 78 *     ..
 79 *     .. External Functions ..
 80       REAL               CLANGE, CLANSY, SLAMCH
 81       EXTERNAL           CLANGE, CLANSY, SLAMCH
 82 *     ..
 83 *     .. External Subroutines ..
 84       EXTERNAL           CGEMM, CGEQLF, CHERK, CLACPY, CLASET, CUNGQL
 85 *     ..
 86 *     .. Intrinsic Functions ..
 87       INTRINSIC          CMPLXMAXMIN, REAL
 88 *     ..
 89 *     .. Scalars in Common ..
 90       CHARACTER*32       SRNAMT
 91 *     ..
 92 *     .. Common blocks ..
 93       COMMON             / SRNAMC / SRNAMT
 94 *     ..
 95 *     .. Executable Statements ..
 96 *
 97       MINMN = MIN( M, N )
 98       EPS = SLAMCH( 'Epsilon' )
 99 *
100 *     Copy the matrix A to the array AF.
101 *
102       CALL CLACPY( 'Full', M, N, A, LDA, AF, LDA )
103 *
104 *     Factorize the matrix A in the array AF.
105 *
106       SRNAMT = 'CGEQLF'
107       CALL CGEQLF( M, N, AF, LDA, TAU, WORK, LWORK, INFO )
108 *
109 *     Copy details of Q
110 *
111       CALL CLASET( 'Full', M, M, ROGUE, ROGUE, Q, LDA )
112       IF( M.GE.N ) THEN
113          IF( N.LT..AND. N.GT.0 )
114      $      CALL CLACPY( 'Full', M-N, N, AF, LDA, Q( 1, M-N+1 ), LDA )
115          IF( N.GT.1 )
116      $      CALL CLACPY( 'Upper', N-1, N-1, AF( M-N+12 ), LDA,
117      $                   Q( M-N+1, M-N+2 ), LDA )
118       ELSE
119          IF( M.GT.1 )
120      $      CALL CLACPY( 'Upper', M-1, M-1, AF( 1, N-M+2 ), LDA,
121      $                   Q( 12 ), LDA )
122       END IF
123 *
124 *     Generate the m-by-m matrix Q
125 *
126       SRNAMT = 'CUNGQL'
127       CALL CUNGQL( M, M, MINMN, Q, LDA, TAU, WORK, LWORK, INFO )
128 *
129 *     Copy L
130 *
131       CALL CLASET( 'Full', M, N, CMPLX( ZERO ), CMPLX( ZERO ), L, LDA )
132       IF( M.GE.N ) THEN
133          IF( N.GT.0 )
134      $      CALL CLACPY( 'Lower', N, N, AF( M-N+11 ), LDA,
135      $                   L( M-N+11 ), LDA )
136       ELSE
137          IF( N.GT..AND. M.GT.0 )
138      $      CALL CLACPY( 'Full', M, N-M, AF, LDA, L, LDA )
139          IF( M.GT.0 )
140      $      CALL CLACPY( 'Lower', M, M, AF( 1, N-M+1 ), LDA,
141      $                   L( 1, N-M+1 ), LDA )
142       END IF
143 *
144 *     Compute L - Q'*A
145 *
146       CALL CGEMM( 'Conjugate transpose''No transpose', M, N, M,
147      $            CMPLX-ONE ), Q, LDA, A, LDA, CMPLX( ONE ), L, LDA )
148 *
149 *     Compute norm( L - Q'*A ) / ( M * norm(A) * EPS ) .
150 *
151       ANORM = CLANGE( '1', M, N, A, LDA, RWORK )
152       RESID = CLANGE( '1', M, N, L, LDA, RWORK )
153       IF( ANORM.GT.ZERO ) THEN
154          RESULT1 ) = ( ( RESID / REALMAX1, M ) ) ) / ANORM ) / EPS
155       ELSE
156          RESULT1 ) = ZERO
157       END IF
158 *
159 *     Compute I - Q'*Q
160 *
161       CALL CLASET( 'Full', M, M, CMPLX( ZERO ), CMPLX( ONE ), L, LDA )
162       CALL CHERK( 'Upper''Conjugate transpose', M, M, -ONE, Q, LDA,
163      $            ONE, L, LDA )
164 *
165 *     Compute norm( I - Q'*Q ) / ( M * EPS ) .
166 *
167       RESID = CLANSY( '1''Upper', M, L, LDA, RWORK )
168 *
169       RESULT2 ) = ( RESID / REALMAX1, M ) ) ) / EPS
170 *
171       RETURN
172 *
173 *     End of CQLT01
174 *
175       END