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SUBROUTINE ZTZSCAL( UPLO, M, N, IOFFD, ALPHA, A, LDA )
*
* -- PBLAS auxiliary routine (version 2.0) --
* University of Tennessee, Knoxville, Oak Ridge National Laboratory,
* and University of California, Berkeley.
* April 1, 1998
*
* .. Scalar Arguments ..
CHARACTER*1 UPLO
INTEGER IOFFD, LDA, M, N
COMPLEX*16 ALPHA
* ..
* .. Array Arguments ..
COMPLEX*16 A( LDA, * )
* ..
*
* Purpose
* =======
*
* ZTZSCAL scales a two-dimensional array A by the scalar alpha.
*
* Arguments
* =========
*
* UPLO (input) CHARACTER*1
* On entry, UPLO specifies which trapezoidal part of the ar-
* ray A is to be scaled as follows:
* = 'L' or 'l': the lower trapezoid of A is scaled,
* = 'U' or 'u': the upper trapezoid of A is scaled,
* = 'D' or 'd': diagonal specified by IOFFD is scaled,
* Otherwise: all of the array A is scaled.
*
* M (input) INTEGER
* On entry, M specifies the number of rows of the array A. M
* must be at least zero.
*
* N (input) INTEGER
* On entry, N specifies the number of columns of the array A.
* N must be at least zero.
*
* IOFFD (input) INTEGER
* On entry, IOFFD specifies the position of the offdiagonal de-
* limiting the upper and lower trapezoidal part of A as follows
* (see the notes below):
*
* IOFFD = 0 specifies the main diagonal A( i, i ),
* with i = 1 ... MIN( M, N ),
* IOFFD > 0 specifies the subdiagonal A( i+IOFFD, i ),
* with i = 1 ... MIN( M-IOFFD, N ),
* IOFFD < 0 specifies the superdiagonal A( i, i-IOFFD ),
* with i = 1 ... MIN( M, N+IOFFD ).
*
* ALPHA (input) COMPLEX*16
* On entry, ALPHA specifies the scalar alpha, i.e., the value
* by which the diagonal and offdiagonal entries of the array A
* as specified by UPLO and IOFFD are scaled.
*
* A (input/output) COMPLEX*16 array
* On entry, A is an array of dimension (LDA,N). Before entry
* with UPLO = 'U' or 'u', the leading m by n part of the array
* A must contain the upper trapezoidal part of the matrix as
* specified by IOFFD to be scaled, and the strictly lower tra-
* pezoidal part of A is not referenced; When UPLO = 'L' or 'l',
* the leading m by n part of the array A must contain the lower
* trapezoidal part of the matrix as specified by IOFFD to be
* scaled, and the strictly upper trapezoidal part of A is not
* referenced. On exit, the entries of the trapezoid part of A
* determined by UPLO and IOFFD are scaled.
*
* LDA (input) INTEGER
* On entry, LDA specifies the leading dimension of the array A.
* LDA must be at least max( 1, M ).
*
* Notes
* =====
* N N
* ---------------------------- -----------
* | d | | |
* M | d 'U' | | 'U' |
* | 'L' 'D' | |d |
* | d | M | d |
* ---------------------------- | 'D' |
* | d |
* IOFFD < 0 | 'L' d |
* | d|
* N | |
* ----------- -----------
* | d 'U'|
* | d | IOFFD > 0
* M | 'D' |
* | d| N
* | 'L' | ----------------------------
* | | | 'U' |
* | | |d |
* | | | 'D' |
* | | | d |
* | | |'L' d |
* ----------- ----------------------------
*
* -- Written on April 1, 1998 by
* Antoine Petitet, University of Tennessee, Knoxville 37996, USA.
*
* =====================================================================
*
* .. Parameters ..
COMPLEX*16 ONE, ZERO
PARAMETER ( ONE = ( 1.0D+0, 0.0D+0 ),
$ ZERO = ( 0.0D+0, 0.0D+0 ) )
* ..
* .. Local Scalars ..
INTEGER J, JTMP, MN
* ..
* .. External Subroutines ..
EXTERNAL ZSCAL, ZTZPAD
* ..
* .. External Functions ..
LOGICAL LSAME
EXTERNAL LSAME
* ..
* .. Intrinsic Functions ..
INTRINSIC MAX, MIN
* ..
* .. Executable Statements ..
*
* Quick return if possible
*
IF( ( M.LE.0 ).OR.( N.LE.0 ).OR.( ALPHA.EQ.ONE ) )
$ RETURN
*
* Start the operations
*
IF( ALPHA.EQ.ZERO ) THEN
CALL ZTZPAD( UPLO, 'N', M, N, IOFFD, ZERO, ZERO, A, LDA )
RETURN
END IF
*
IF( LSAME( UPLO, 'L' ) ) THEN
*
* Scales the lower triangular part of the array by ALPHA.
*
MN = MAX( 0, -IOFFD )
DO 10 J = 1, MIN( MN, N )
CALL ZSCAL( M, ALPHA, A( 1, J ), 1 )
10 CONTINUE
DO 20 J = MN + 1, MIN( M - IOFFD, N )
JTMP = J + IOFFD
IF( M.GE.JTMP )
$ CALL ZSCAL( M-JTMP+1, ALPHA, A( JTMP, J ), 1 )
20 CONTINUE
*
ELSE IF( LSAME( UPLO, 'U' ) ) THEN
*
* Scales the upper triangular part of the array by ALPHA.
*
MN = MIN( M - IOFFD, N )
DO 30 J = MAX( 0, -IOFFD ) + 1, MN
CALL ZSCAL( J + IOFFD, ALPHA, A( 1, J ), 1 )
30 CONTINUE
DO 40 J = MAX( 0, MN ) + 1, N
CALL ZSCAL( M, ALPHA, A( 1, J ), 1 )
40 CONTINUE
*
ELSE IF( LSAME( UPLO, 'D' ) ) THEN
*
* Scales the diagonal entries by ALPHA.
*
DO 50 J = MAX( 0, -IOFFD ) + 1, MIN( M - IOFFD, N )
JTMP = J + IOFFD
A( JTMP, J ) = ALPHA * A( JTMP, J )
50 CONTINUE
*
ELSE
*
* Scales the entire array by ALPHA.
*
DO 60 J = 1, N
CALL ZSCAL( M, ALPHA, A( 1, J ), 1 )
60 CONTINUE
*
END IF
*
RETURN
*
* End of ZTZSCAL
*
END
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