testdata/lapack/TESTING/LIN/clattb.f
*> \brief \b CLATTB
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition:
* ===========
*
* SUBROUTINE CLATTB( IMAT, UPLO, TRANS, DIAG, ISEED, N, KD, AB,
* LDAB, B, WORK, RWORK, INFO )
*
* .. Scalar Arguments ..
* CHARACTER DIAG, TRANS, UPLO
* INTEGER IMAT, INFO, KD, LDAB, N
* ..
* .. Array Arguments ..
* INTEGER ISEED( 4 )
* REAL RWORK( * )
* COMPLEX AB( LDAB, * ), B( * ), WORK( * )
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> CLATTB generates a triangular test matrix in 2-dimensional storage.
*> IMAT and UPLO uniquely specify the properties of the test matrix,
*> which is returned in the array A.
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in] IMAT
*> \verbatim
*> IMAT is INTEGER
*> An integer key describing which matrix to generate for this
*> path.
*> \endverbatim
*>
*> \param[in] UPLO
*> \verbatim
*> UPLO is CHARACTER*1
*> Specifies whether the matrix A will be upper or lower
*> triangular.
*> = 'U': Upper triangular
*> = 'L': Lower triangular
*> \endverbatim
*>
*> \param[in] TRANS
*> \verbatim
*> TRANS is CHARACTER*1
*> Specifies whether the matrix or its transpose will be used.
*> = 'N': No transpose
*> = 'T': Transpose
*> = 'C': Conjugate transpose (= transpose)
*> \endverbatim
*>
*> \param[out] DIAG
*> \verbatim
*> DIAG is CHARACTER*1
*> Specifies whether or not the matrix A is unit triangular.
*> = 'N': Non-unit triangular
*> = 'U': Unit triangular
*> \endverbatim
*>
*> \param[in,out] ISEED
*> \verbatim
*> ISEED is INTEGER array, dimension (4)
*> The seed vector for the random number generator (used in
*> CLATMS). Modified on exit.
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*> N is INTEGER
*> The order of the matrix to be generated.
*> \endverbatim
*>
*> \param[in] KD
*> \verbatim
*> KD is INTEGER
*> The number of superdiagonals or subdiagonals of the banded
*> triangular matrix A. KD >= 0.
*> \endverbatim
*>
*> \param[out] AB
*> \verbatim
*> AB is COMPLEX array, dimension (LDAB,N)
*> The upper or lower triangular banded matrix A, stored in the
*> first KD+1 rows of AB. Let j be a column of A, 1<=j<=n.
*> If UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j.
*> If UPLO = 'L', AB(1+i-j,j) = A(i,j) for j<=i<=min(n,j+kd).
*> \endverbatim
*>
*> \param[in] LDAB
*> \verbatim
*> LDAB is INTEGER
*> The leading dimension of the array AB. LDAB >= KD+1.
*> \endverbatim
*>
*> \param[out] B
*> \verbatim
*> B is COMPLEX array, dimension (N)
*> \endverbatim
*>
*> \param[out] WORK
*> \verbatim
*> WORK is COMPLEX array, dimension (2*N)
*> \endverbatim
*>
*> \param[out] RWORK
*> \verbatim
*> RWORK is REAL array, dimension (N)
*> \endverbatim
*>
*> \param[out] INFO
*> \verbatim
*> INFO is INTEGER
*> = 0: successful exit
*> < 0: if INFO = -i, the i-th argument had an illegal value
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date December 2016
*
*> \ingroup complex_lin
*
* =====================================================================
SUBROUTINE CLATTB( IMAT, UPLO, TRANS, DIAG, ISEED, N, KD, AB,
$ LDAB, B, WORK, RWORK, INFO )
*
* -- LAPACK test routine (version 3.7.0) --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* December 2016
*
* .. Scalar Arguments ..
CHARACTER DIAG, TRANS, UPLO
INTEGER IMAT, INFO, KD, LDAB, N
* ..
* .. Array Arguments ..
INTEGER ISEED( 4 )
REAL RWORK( * )
COMPLEX AB( LDAB, * ), B( * ), WORK( * )
* ..
*
* =====================================================================
*
* .. Parameters ..
REAL ONE, TWO, ZERO
PARAMETER ( ONE = 1.0E+0, TWO = 2.0E+0, ZERO = 0.0E+0 )
* ..
* .. Local Scalars ..
LOGICAL UPPER
CHARACTER DIST, PACKIT, TYPE
CHARACTER*3 PATH
INTEGER I, IOFF, IY, J, JCOUNT, KL, KU, LENJ, MODE
REAL ANORM, BIGNUM, BNORM, BSCAL, CNDNUM, REXP,
$ SFAC, SMLNUM, TEXP, TLEFT, TNORM, TSCAL, ULP,
$ UNFL
COMPLEX PLUS1, PLUS2, STAR1
* ..
* .. External Functions ..
LOGICAL LSAME
INTEGER ICAMAX
REAL SLAMCH, SLARND
COMPLEX CLARND
EXTERNAL LSAME, ICAMAX, SLAMCH, SLARND, CLARND
* ..
* .. External Subroutines ..
EXTERNAL CCOPY, CLARNV, CLATB4, CLATMS, CSSCAL, CSWAP,
$ SLABAD, SLARNV
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS, CMPLX, MAX, MIN, REAL, SQRT
* ..
* .. Executable Statements ..
*
PATH( 1: 1 ) = 'Complex precision'
PATH( 2: 3 ) = 'TB'
UNFL = SLAMCH( 'Safe minimum' )
ULP = SLAMCH( 'Epsilon' )*SLAMCH( 'Base' )
SMLNUM = UNFL
BIGNUM = ( ONE-ULP ) / SMLNUM
CALL SLABAD( SMLNUM, BIGNUM )
IF( ( IMAT.GE.6 .AND. IMAT.LE.9 ) .OR. IMAT.EQ.17 ) THEN
DIAG = 'U'
ELSE
DIAG = 'N'
END IF
INFO = 0
*
* Quick return if N.LE.0.
*
IF( N.LE.0 )
$ RETURN
*
* Call CLATB4 to set parameters for CLATMS.
*
UPPER = LSAME( UPLO, 'U' )
IF( UPPER ) THEN
CALL CLATB4( PATH, IMAT, N, N, TYPE, KL, KU, ANORM, MODE,
$ CNDNUM, DIST )
KU = KD
IOFF = 1 + MAX( 0, KD-N+1 )
KL = 0
PACKIT = 'Q'
ELSE
CALL CLATB4( PATH, -IMAT, N, N, TYPE, KL, KU, ANORM, MODE,
$ CNDNUM, DIST )
KL = KD
IOFF = 1
KU = 0
PACKIT = 'B'
END IF
*
* IMAT <= 5: Non-unit triangular matrix
*
IF( IMAT.LE.5 ) THEN
CALL CLATMS( N, N, DIST, ISEED, TYPE, RWORK, MODE, CNDNUM,
$ ANORM, KL, KU, PACKIT, AB( IOFF, 1 ), LDAB, WORK,
$ INFO )
*
* IMAT > 5: Unit triangular matrix
* The diagonal is deliberately set to something other than 1.
*
* IMAT = 6: Matrix is the identity
*
ELSE IF( IMAT.EQ.6 ) THEN
IF( UPPER ) THEN
DO 20 J = 1, N
DO 10 I = MAX( 1, KD+2-J ), KD
AB( I, J ) = ZERO
10 CONTINUE
AB( KD+1, J ) = J
20 CONTINUE
ELSE
DO 40 J = 1, N
AB( 1, J ) = J
DO 30 I = 2, MIN( KD+1, N-J+1 )
AB( I, J ) = ZERO
30 CONTINUE
40 CONTINUE
END IF
*
* IMAT > 6: Non-trivial unit triangular matrix
*
* A unit triangular matrix T with condition CNDNUM is formed.
* In this version, T only has bandwidth 2, the rest of it is zero.
*
ELSE IF( IMAT.LE.9 ) THEN
TNORM = SQRT( CNDNUM )
*
* Initialize AB to zero.
*
IF( UPPER ) THEN
DO 60 J = 1, N
DO 50 I = MAX( 1, KD+2-J ), KD
AB( I, J ) = ZERO
50 CONTINUE
AB( KD+1, J ) = REAL( J )
60 CONTINUE
ELSE
DO 80 J = 1, N
DO 70 I = 2, MIN( KD+1, N-J+1 )
AB( I, J ) = ZERO
70 CONTINUE
AB( 1, J ) = REAL( J )
80 CONTINUE
END IF
*
* Special case: T is tridiagonal. Set every other offdiagonal
* so that the matrix has norm TNORM+1.
*
IF( KD.EQ.1 ) THEN
IF( UPPER ) THEN
AB( 1, 2 ) = TNORM*CLARND( 5, ISEED )
LENJ = ( N-3 ) / 2
CALL CLARNV( 2, ISEED, LENJ, WORK )
DO 90 J = 1, LENJ
AB( 1, 2*( J+1 ) ) = TNORM*WORK( J )
90 CONTINUE
ELSE
AB( 2, 1 ) = TNORM*CLARND( 5, ISEED )
LENJ = ( N-3 ) / 2
CALL CLARNV( 2, ISEED, LENJ, WORK )
DO 100 J = 1, LENJ
AB( 2, 2*J+1 ) = TNORM*WORK( J )
100 CONTINUE
END IF
ELSE IF( KD.GT.1 ) THEN
*
* Form a unit triangular matrix T with condition CNDNUM. T is
* given by
* | 1 + * |
* | 1 + |
* T = | 1 + * |
* | 1 + |
* | 1 + * |
* | 1 + |
* | . . . |
* Each element marked with a '*' is formed by taking the product
* of the adjacent elements marked with '+'. The '*'s can be
* chosen freely, and the '+'s are chosen so that the inverse of
* T will have elements of the same magnitude as T.
*
* The two offdiagonals of T are stored in WORK.
*
STAR1 = TNORM*CLARND( 5, ISEED )
SFAC = SQRT( TNORM )
PLUS1 = SFAC*CLARND( 5, ISEED )
DO 110 J = 1, N, 2
PLUS2 = STAR1 / PLUS1
WORK( J ) = PLUS1
WORK( N+J ) = STAR1
IF( J+1.LE.N ) THEN
WORK( J+1 ) = PLUS2
WORK( N+J+1 ) = ZERO
PLUS1 = STAR1 / PLUS2
*
* Generate a new *-value with norm between sqrt(TNORM)
* and TNORM.
*
REXP = SLARND( 2, ISEED )
IF( REXP.LT.ZERO ) THEN
STAR1 = -SFAC**( ONE-REXP )*CLARND( 5, ISEED )
ELSE
STAR1 = SFAC**( ONE+REXP )*CLARND( 5, ISEED )
END IF
END IF
110 CONTINUE
*
* Copy the tridiagonal T to AB.
*
IF( UPPER ) THEN
CALL CCOPY( N-1, WORK, 1, AB( KD, 2 ), LDAB )
CALL CCOPY( N-2, WORK( N+1 ), 1, AB( KD-1, 3 ), LDAB )
ELSE
CALL CCOPY( N-1, WORK, 1, AB( 2, 1 ), LDAB )
CALL CCOPY( N-2, WORK( N+1 ), 1, AB( 3, 1 ), LDAB )
END IF
END IF
*
* IMAT > 9: Pathological test cases. These triangular matrices
* are badly scaled or badly conditioned, so when used in solving a
* triangular system they may cause overflow in the solution vector.
*
ELSE IF( IMAT.EQ.10 ) THEN
*
* Type 10: Generate a triangular matrix with elements between
* -1 and 1. Give the diagonal norm 2 to make it well-conditioned.
* Make the right hand side large so that it requires scaling.
*
IF( UPPER ) THEN
DO 120 J = 1, N
LENJ = MIN( J-1, KD )
CALL CLARNV( 4, ISEED, LENJ, AB( KD+1-LENJ, J ) )
AB( KD+1, J ) = CLARND( 5, ISEED )*TWO
120 CONTINUE
ELSE
DO 130 J = 1, N
LENJ = MIN( N-J, KD )
IF( LENJ.GT.0 )
$ CALL CLARNV( 4, ISEED, LENJ, AB( 2, J ) )
AB( 1, J ) = CLARND( 5, ISEED )*TWO
130 CONTINUE
END IF
*
* Set the right hand side so that the largest value is BIGNUM.
*
CALL CLARNV( 2, ISEED, N, B )
IY = ICAMAX( N, B, 1 )
BNORM = ABS( B( IY ) )
BSCAL = BIGNUM / MAX( ONE, BNORM )
CALL CSSCAL( N, BSCAL, B, 1 )
*
ELSE IF( IMAT.EQ.11 ) THEN
*
* Type 11: Make the first diagonal element in the solve small to
* cause immediate overflow when dividing by T(j,j).
* In type 11, the offdiagonal elements are small (CNORM(j) < 1).
*
CALL CLARNV( 2, ISEED, N, B )
TSCAL = ONE / REAL( KD+1 )
IF( UPPER ) THEN
DO 140 J = 1, N
LENJ = MIN( J-1, KD )
IF( LENJ.GT.0 ) THEN
CALL CLARNV( 4, ISEED, LENJ, AB( KD+2-LENJ, J ) )
CALL CSSCAL( LENJ, TSCAL, AB( KD+2-LENJ, J ), 1 )
END IF
AB( KD+1, J ) = CLARND( 5, ISEED )
140 CONTINUE
AB( KD+1, N ) = SMLNUM*AB( KD+1, N )
ELSE
DO 150 J = 1, N
LENJ = MIN( N-J, KD )
IF( LENJ.GT.0 ) THEN
CALL CLARNV( 4, ISEED, LENJ, AB( 2, J ) )
CALL CSSCAL( LENJ, TSCAL, AB( 2, J ), 1 )
END IF
AB( 1, J ) = CLARND( 5, ISEED )
150 CONTINUE
AB( 1, 1 ) = SMLNUM*AB( 1, 1 )
END IF
*
ELSE IF( IMAT.EQ.12 ) THEN
*
* Type 12: Make the first diagonal element in the solve small to
* cause immediate overflow when dividing by T(j,j).
* In type 12, the offdiagonal elements are O(1) (CNORM(j) > 1).
*
CALL CLARNV( 2, ISEED, N, B )
IF( UPPER ) THEN
DO 160 J = 1, N
LENJ = MIN( J-1, KD )
IF( LENJ.GT.0 )
$ CALL CLARNV( 4, ISEED, LENJ, AB( KD+2-LENJ, J ) )
AB( KD+1, J ) = CLARND( 5, ISEED )
160 CONTINUE
AB( KD+1, N ) = SMLNUM*AB( KD+1, N )
ELSE
DO 170 J = 1, N
LENJ = MIN( N-J, KD )
IF( LENJ.GT.0 )
$ CALL CLARNV( 4, ISEED, LENJ, AB( 2, J ) )
AB( 1, J ) = CLARND( 5, ISEED )
170 CONTINUE
AB( 1, 1 ) = SMLNUM*AB( 1, 1 )
END IF
*
ELSE IF( IMAT.EQ.13 ) THEN
*
* Type 13: T is diagonal with small numbers on the diagonal to
* make the growth factor underflow, but a small right hand side
* chosen so that the solution does not overflow.
*
IF( UPPER ) THEN
JCOUNT = 1
DO 190 J = N, 1, -1
DO 180 I = MAX( 1, KD+1-( J-1 ) ), KD
AB( I, J ) = ZERO
180 CONTINUE
IF( JCOUNT.LE.2 ) THEN
AB( KD+1, J ) = SMLNUM*CLARND( 5, ISEED )
ELSE
AB( KD+1, J ) = CLARND( 5, ISEED )
END IF
JCOUNT = JCOUNT + 1
IF( JCOUNT.GT.4 )
$ JCOUNT = 1
190 CONTINUE
ELSE
JCOUNT = 1
DO 210 J = 1, N
DO 200 I = 2, MIN( N-J+1, KD+1 )
AB( I, J ) = ZERO
200 CONTINUE
IF( JCOUNT.LE.2 ) THEN
AB( 1, J ) = SMLNUM*CLARND( 5, ISEED )
ELSE
AB( 1, J ) = CLARND( 5, ISEED )
END IF
JCOUNT = JCOUNT + 1
IF( JCOUNT.GT.4 )
$ JCOUNT = 1
210 CONTINUE
END IF
*
* Set the right hand side alternately zero and small.
*
IF( UPPER ) THEN
B( 1 ) = ZERO
DO 220 I = N, 2, -2
B( I ) = ZERO
B( I-1 ) = SMLNUM*CLARND( 5, ISEED )
220 CONTINUE
ELSE
B( N ) = ZERO
DO 230 I = 1, N - 1, 2
B( I ) = ZERO
B( I+1 ) = SMLNUM*CLARND( 5, ISEED )
230 CONTINUE
END IF
*
ELSE IF( IMAT.EQ.14 ) THEN
*
* Type 14: Make the diagonal elements small to cause gradual
* overflow when dividing by T(j,j). To control the amount of
* scaling needed, the matrix is bidiagonal.
*
TEXP = ONE / REAL( KD+1 )
TSCAL = SMLNUM**TEXP
CALL CLARNV( 4, ISEED, N, B )
IF( UPPER ) THEN
DO 250 J = 1, N
DO 240 I = MAX( 1, KD+2-J ), KD
AB( I, J ) = ZERO
240 CONTINUE
IF( J.GT.1 .AND. KD.GT.0 )
$ AB( KD, J ) = CMPLX( -ONE, -ONE )
AB( KD+1, J ) = TSCAL*CLARND( 5, ISEED )
250 CONTINUE
B( N ) = CMPLX( ONE, ONE )
ELSE
DO 270 J = 1, N
DO 260 I = 3, MIN( N-J+1, KD+1 )
AB( I, J ) = ZERO
260 CONTINUE
IF( J.LT.N .AND. KD.GT.0 )
$ AB( 2, J ) = CMPLX( -ONE, -ONE )
AB( 1, J ) = TSCAL*CLARND( 5, ISEED )
270 CONTINUE
B( 1 ) = CMPLX( ONE, ONE )
END IF
*
ELSE IF( IMAT.EQ.15 ) THEN
*
* Type 15: One zero diagonal element.
*
IY = N / 2 + 1
IF( UPPER ) THEN
DO 280 J = 1, N
LENJ = MIN( J, KD+1 )
CALL CLARNV( 4, ISEED, LENJ, AB( KD+2-LENJ, J ) )
IF( J.NE.IY ) THEN
AB( KD+1, J ) = CLARND( 5, ISEED )*TWO
ELSE
AB( KD+1, J ) = ZERO
END IF
280 CONTINUE
ELSE
DO 290 J = 1, N
LENJ = MIN( N-J+1, KD+1 )
CALL CLARNV( 4, ISEED, LENJ, AB( 1, J ) )
IF( J.NE.IY ) THEN
AB( 1, J ) = CLARND( 5, ISEED )*TWO
ELSE
AB( 1, J ) = ZERO
END IF
290 CONTINUE
END IF
CALL CLARNV( 2, ISEED, N, B )
CALL CSSCAL( N, TWO, B, 1 )
*
ELSE IF( IMAT.EQ.16 ) THEN
*
* Type 16: Make the offdiagonal elements large to cause overflow
* when adding a column of T. In the non-transposed case, the
* matrix is constructed to cause overflow when adding a column in
* every other step.
*
TSCAL = UNFL / ULP
TSCAL = ( ONE-ULP ) / TSCAL
DO 310 J = 1, N
DO 300 I = 1, KD + 1
AB( I, J ) = ZERO
300 CONTINUE
310 CONTINUE
TEXP = ONE
IF( KD.GT.0 ) THEN
IF( UPPER ) THEN
DO 330 J = N, 1, -KD
DO 320 I = J, MAX( 1, J-KD+1 ), -2
AB( 1+( J-I ), I ) = -TSCAL / REAL( KD+2 )
AB( KD+1, I ) = ONE
B( I ) = TEXP*( ONE-ULP )
IF( I.GT.MAX( 1, J-KD+1 ) ) THEN
AB( 2+( J-I ), I-1 ) = -( TSCAL / REAL( KD+2 ) )
$ / REAL( KD+3 )
AB( KD+1, I-1 ) = ONE
B( I-1 ) = TEXP*REAL( ( KD+1 )*( KD+1 )+KD )
END IF
TEXP = TEXP*TWO
320 CONTINUE
B( MAX( 1, J-KD+1 ) ) = ( REAL( KD+2 ) /
$ REAL( KD+3 ) )*TSCAL
330 CONTINUE
ELSE
DO 350 J = 1, N, KD
TEXP = ONE
LENJ = MIN( KD+1, N-J+1 )
DO 340 I = J, MIN( N, J+KD-1 ), 2
AB( LENJ-( I-J ), J ) = -TSCAL / REAL( KD+2 )
AB( 1, J ) = ONE
B( J ) = TEXP*( ONE-ULP )
IF( I.LT.MIN( N, J+KD-1 ) ) THEN
AB( LENJ-( I-J+1 ), I+1 ) = -( TSCAL /
$ REAL( KD+2 ) ) / REAL( KD+3 )
AB( 1, I+1 ) = ONE
B( I+1 ) = TEXP*REAL( ( KD+1 )*( KD+1 )+KD )
END IF
TEXP = TEXP*TWO
340 CONTINUE
B( MIN( N, J+KD-1 ) ) = ( REAL( KD+2 ) /
$ REAL( KD+3 ) )*TSCAL
350 CONTINUE
END IF
END IF
*
ELSE IF( IMAT.EQ.17 ) THEN
*
* Type 17: Generate a unit triangular matrix with elements
* between -1 and 1, and make the right hand side large so that it
* requires scaling.
*
IF( UPPER ) THEN
DO 360 J = 1, N
LENJ = MIN( J-1, KD )
CALL CLARNV( 4, ISEED, LENJ, AB( KD+1-LENJ, J ) )
AB( KD+1, J ) = REAL( J )
360 CONTINUE
ELSE
DO 370 J = 1, N
LENJ = MIN( N-J, KD )
IF( LENJ.GT.0 )
$ CALL CLARNV( 4, ISEED, LENJ, AB( 2, J ) )
AB( 1, J ) = REAL( J )
370 CONTINUE
END IF
*
* Set the right hand side so that the largest value is BIGNUM.
*
CALL CLARNV( 2, ISEED, N, B )
IY = ICAMAX( N, B, 1 )
BNORM = ABS( B( IY ) )
BSCAL = BIGNUM / MAX( ONE, BNORM )
CALL CSSCAL( N, BSCAL, B, 1 )
*
ELSE IF( IMAT.EQ.18 ) THEN
*
* Type 18: Generate a triangular matrix with elements between
* BIGNUM/(KD+1) and BIGNUM so that at least one of the column
* norms will exceed BIGNUM.
* 1/3/91: CLATBS no longer can handle this case
*
TLEFT = BIGNUM / REAL( KD+1 )
TSCAL = BIGNUM*( REAL( KD+1 ) / REAL( KD+2 ) )
IF( UPPER ) THEN
DO 390 J = 1, N
LENJ = MIN( J, KD+1 )
CALL CLARNV( 5, ISEED, LENJ, AB( KD+2-LENJ, J ) )
CALL SLARNV( 1, ISEED, LENJ, RWORK( KD+2-LENJ ) )
DO 380 I = KD + 2 - LENJ, KD + 1
AB( I, J ) = AB( I, J )*( TLEFT+RWORK( I )*TSCAL )
380 CONTINUE
390 CONTINUE
ELSE
DO 410 J = 1, N
LENJ = MIN( N-J+1, KD+1 )
CALL CLARNV( 5, ISEED, LENJ, AB( 1, J ) )
CALL SLARNV( 1, ISEED, LENJ, RWORK )
DO 400 I = 1, LENJ
AB( I, J ) = AB( I, J )*( TLEFT+RWORK( I )*TSCAL )
400 CONTINUE
410 CONTINUE
END IF
CALL CLARNV( 2, ISEED, N, B )
CALL CSSCAL( N, TWO, B, 1 )
END IF
*
* Flip the matrix if the transpose will be used.
*
IF( .NOT.LSAME( TRANS, 'N' ) ) THEN
IF( UPPER ) THEN
DO 420 J = 1, N / 2
LENJ = MIN( N-2*J+1, KD+1 )
CALL CSWAP( LENJ, AB( KD+1, J ), LDAB-1,
$ AB( KD+2-LENJ, N-J+1 ), -1 )
420 CONTINUE
ELSE
DO 430 J = 1, N / 2
LENJ = MIN( N-2*J+1, KD+1 )
CALL CSWAP( LENJ, AB( 1, J ), 1, AB( LENJ, N-J+2-LENJ ),
$ -LDAB+1 )
430 CONTINUE
END IF
END IF
*
RETURN
*
* End of CLATTB
*
END