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SUBROUTINE MB01PD( SCUN, TYPE, M, N, KL, KU, ANRM, NBL, NROWS, A,
$ LDA, INFO )
C
C SLICOT RELEASE 5.0.
C
C Copyright (c) 2002-2009 NICONET e.V.
C
C This program is free software: you can redistribute it and/or
C modify it under the terms of the GNU General Public License as
C published by the Free Software Foundation, either version 2 of
C the License, or (at your option) any later version.
C
C This program is distributed in the hope that it will be useful,
C but WITHOUT ANY WARRANTY; without even the implied warranty of
C MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
C GNU General Public License for more details.
C
C You should have received a copy of the GNU General Public License
C along with this program. If not, see
C <http://www.gnu.org/licenses/>.
C
C PURPOSE
C
C To scale a matrix or undo scaling. Scaling is performed, if
C necessary, so that the matrix norm will be in a safe range of
C representable numbers.
C
C ARGUMENTS
C
C Mode Parameters
C
C SCUN CHARACTER*1
C SCUN indicates the operation to be performed.
C = 'S': scale the matrix.
C = 'U': undo scaling of the matrix.
C
C TYPE CHARACTER*1
C TYPE indicates the storage type of the input matrix.
C = 'G': A is a full matrix.
C = 'L': A is a (block) lower triangular matrix.
C = 'U': A is an (block) upper triangular matrix.
C = 'H': A is an (block) upper Hessenberg matrix.
C = 'B': A is a symmetric band matrix with lower bandwidth
C KL and upper bandwidth KU and with the only the
C lower half stored.
C = 'Q': A is a symmetric band matrix with lower bandwidth
C KL and upper bandwidth KU and with the only the
C upper half stored.
C = 'Z': A is a band matrix with lower bandwidth KL and
C upper bandwidth KU.
C
C Input/Output Parameters
C
C M (input) INTEGER
C The number of rows of the matrix A. M >= 0.
C
C N (input) INTEGER
C The number of columns of the matrix A. N >= 0.
C
C KL (input) INTEGER
C The lower bandwidth of A. Referenced only if TYPE = 'B',
C 'Q' or 'Z'.
C
C KU (input) INTEGER
C The upper bandwidth of A. Referenced only if TYPE = 'B',
C 'Q' or 'Z'.
C
C ANRM (input) DOUBLE PRECISION
C The norm of the initial matrix A. ANRM >= 0.
C When ANRM = 0 then an immediate return is effected.
C ANRM should be preserved between the call of the routine
C with SCUN = 'S' and the corresponding one with SCUN = 'U'.
C
C NBL (input) INTEGER
C The number of diagonal blocks of the matrix A, if it has a
C block structure. To specify that matrix A has no block
C structure, set NBL = 0. NBL >= 0.
C
C NROWS (input) INTEGER array, dimension max(1,NBL)
C NROWS(i) contains the number of rows and columns of the
C i-th diagonal block of matrix A. The sum of the values
C NROWS(i), for i = 1: NBL, should be equal to min(M,N).
C The elements of the array NROWS are not referenced if
C NBL = 0.
C
C A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
C On entry, the leading M by N part of this array must
C contain the matrix to be scaled/unscaled.
C On exit, the leading M by N part of A will contain
C the modified matrix.
C The storage mode of A is specified by TYPE.
C
C LDA (input) INTEGER
C The leading dimension of the array A. LDA >= max(1,M).
C
C Error Indicator
C
C INFO (output) INTEGER
C = 0: successful exit
C < 0: if INFO = -i, the i-th argument had an illegal
C value.
C
C METHOD
C
C Denote by ANRM the norm of the matrix, and by SMLNUM and BIGNUM,
C two positive numbers near the smallest and largest safely
C representable numbers, respectively. The matrix is scaled, if
C needed, such that the norm of the result is in the range
C [SMLNUM, BIGNUM]. The scaling factor is represented as a ratio
C of two numbers, one of them being ANRM, and the other one either
C SMLNUM or BIGNUM, depending on ANRM being less than SMLNUM or
C larger than BIGNUM, respectively. For undoing the scaling, the
C norm is again compared with SMLNUM or BIGNUM, and the reciprocal
C of the previous scaling factor is used.
C
C CONTRIBUTOR
C
C V. Sima, Katholieke Univ. Leuven, Belgium, Nov. 1996.
C
C REVISIONS
C
C Oct. 2001, V. Sima, Research Institute for Informatics, Bucharest.
C
C ******************************************************************
C
C .. Parameters ..
DOUBLE PRECISION ZERO, ONE
PARAMETER ( ZERO = 0.0D0, ONE = 1.0D0 )
C .. Scalar Arguments ..
CHARACTER SCUN, TYPE
INTEGER INFO, KL, KU, LDA, M, MN, N, NBL
DOUBLE PRECISION ANRM
C .. Array Arguments ..
INTEGER NROWS ( * )
DOUBLE PRECISION A( LDA, * )
C .. Local Scalars ..
LOGICAL FIRST, LSCALE
INTEGER I, ISUM, ITYPE
DOUBLE PRECISION BIGNUM, SMLNUM
C .. External Functions ..
LOGICAL LSAME
DOUBLE PRECISION DLAMCH
EXTERNAL DLAMCH, LSAME
C ..
C .. External Subroutines ..
EXTERNAL DLABAD, MB01QD, XERBLA
C .. Intrinsic Functions ..
INTRINSIC MAX, MIN
C .. Save statement ..
SAVE BIGNUM, FIRST, SMLNUM
C .. Data statements ..
DATA FIRST/.TRUE./
C ..
C .. Executable Statements ..
C
C Test the input scalar arguments.
C
INFO = 0
LSCALE = LSAME( SCUN, 'S' )
IF( LSAME( TYPE, 'G' ) ) THEN
ITYPE = 0
ELSE IF( LSAME( TYPE, 'L' ) ) THEN
ITYPE = 1
ELSE IF( LSAME( TYPE, 'U' ) ) THEN
ITYPE = 2
ELSE IF( LSAME( TYPE, 'H' ) ) THEN
ITYPE = 3
ELSE IF( LSAME( TYPE, 'B' ) ) THEN
ITYPE = 4
ELSE IF( LSAME( TYPE, 'Q' ) ) THEN
ITYPE = 5
ELSE IF( LSAME( TYPE, 'Z' ) ) THEN
ITYPE = 6
ELSE
ITYPE = -1
END IF
C
MN = MIN( M, N )
C
ISUM = 0
IF( NBL.GT.0 ) THEN
DO 10 I = 1, NBL
ISUM = ISUM + NROWS(I)
10 CONTINUE
END IF
C
IF( .NOT.LSCALE .AND. .NOT.LSAME( SCUN, 'U' ) ) THEN
INFO = -1
ELSE IF( ITYPE.EQ.-1 ) THEN
INFO = -2
ELSE IF( M.LT.0 ) THEN
INFO = -3
ELSE IF( N.LT.0 .OR.
$ ( ( ITYPE.EQ.4 .OR. ITYPE.EQ.5 ) .AND. N.NE.M ) ) THEN
INFO = -4
ELSE IF( ANRM.LT.ZERO ) THEN
INFO = -7
ELSE IF( NBL.LT.0 ) THEN
INFO = -8
ELSE IF( NBL.GT.0 .AND. ISUM.NE.MN ) THEN
INFO = -9
ELSE IF( ITYPE.LE.3 .AND. LDA.LT.MAX( 1, M ) ) THEN
INFO = -11
ELSE IF( ITYPE.GE.4 ) THEN
IF( KL.LT.0 .OR. KL.GT.MAX( M-1, 0 ) ) THEN
INFO = -5
ELSE IF( KU.LT.0 .OR. KU.GT.MAX( N-1, 0 ) .OR.
$ ( ( ITYPE.EQ.4 .OR. ITYPE.EQ.5 ) .AND. KL.NE.KU ) )
$ THEN
INFO = -6
ELSE IF( ( ITYPE.EQ.4 .AND. LDA.LT.KL+1 ) .OR.
$ ( ITYPE.EQ.5 .AND. LDA.LT.KU+1 ) .OR.
$ ( ITYPE.EQ.6 .AND. LDA.LT.2*KL+KU+1 ) ) THEN
INFO = -11
END IF
END IF
C
IF( INFO.NE.0 ) THEN
CALL XERBLA( 'MB01PD', -INFO )
RETURN
END IF
C
C Quick return if possible.
C
IF( MN.EQ.0 .OR. ANRM.EQ.ZERO )
$ RETURN
C
IF ( FIRST ) THEN
C
C Get machine parameters.
C
SMLNUM = DLAMCH( 'S' ) / DLAMCH( 'P' )
BIGNUM = ONE / SMLNUM
CALL DLABAD( SMLNUM, BIGNUM )
FIRST = .FALSE.
END IF
C
IF ( LSCALE ) THEN
C
C Scale A, if its norm is outside range [SMLNUM,BIGNUM].
C
IF( ANRM.LT.SMLNUM ) THEN
C
C Scale matrix norm up to SMLNUM.
C
CALL MB01QD( TYPE, M, N, KL, KU, ANRM, SMLNUM, NBL, NROWS,
$ A, LDA, INFO )
ELSE IF( ANRM.GT.BIGNUM ) THEN
C
C Scale matrix norm down to BIGNUM.
C
CALL MB01QD( TYPE, M, N, KL, KU, ANRM, BIGNUM, NBL, NROWS,
$ A, LDA, INFO )
END IF
C
ELSE
C
C Undo scaling.
C
IF( ANRM.LT.SMLNUM ) THEN
CALL MB01QD( TYPE, M, N, KL, KU, SMLNUM, ANRM, NBL, NROWS,
$ A, LDA, INFO )
ELSE IF( ANRM.GT.BIGNUM ) THEN
CALL MB01QD( TYPE, M, N, KL, KU, BIGNUM, ANRM, NBL, NROWS,
$ A, LDA, INFO )
END IF
END IF
C
RETURN
C *** Last line of MB01PD ***
END
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