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SUBROUTINE ZDRSCL( N, SA, SX, INCX )
*
* -- LAPACK auxiliary routine (version 3.0) --
* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
* Courant Institute, Argonne National Lab, and Rice University
* September 30, 1994
*
* .. Scalar Arguments ..
INTEGER INCX, N
DOUBLE PRECISION SA
* ..
* .. Array Arguments ..
COMPLEX*16 SX( * )
* ..
*
* Purpose
* =======
*
* ZDRSCL multiplies an n-element complex vector x by the real scalar
* 1/a. This is done without overflow or underflow as long as
* the final result x/a does not overflow or underflow.
*
* Arguments
* =========
*
* N (input) INTEGER
* The number of components of the vector x.
*
* SA (input) DOUBLE PRECISION
* The scalar a which is used to divide each component of x.
* SA must be >= 0, or the subroutine will divide by zero.
*
* SX (input/output) COMPLEX*16 array, dimension
* (1+(N-1)*abs(INCX))
* The n-element vector x.
*
* INCX (input) INTEGER
* The increment between successive values of the vector SX.
* > 0: SX(1) = X(1) and SX(1+(i-1)*INCX) = x(i), 1< i<= n
*
* =====================================================================
*
* .. Parameters ..
DOUBLE PRECISION ZERO, ONE
PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0 )
* ..
* .. Local Scalars ..
LOGICAL DONE
DOUBLE PRECISION BIGNUM, CDEN, CDEN1, CNUM, CNUM1, MUL, SMLNUM
* ..
* .. External Functions ..
DOUBLE PRECISION DLAMCH
EXTERNAL DLAMCH
* ..
* .. External Subroutines ..
EXTERNAL DLABAD, ZDSCAL
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS
* ..
* .. Executable Statements ..
*
* Quick return if possible
*
IF( N.LE.0 )
$ RETURN
*
* Get machine parameters
*
SMLNUM = DLAMCH( 'S' )
BIGNUM = ONE / SMLNUM
CALL DLABAD( SMLNUM, BIGNUM )
*
* Initialize the denominator to SA and the numerator to 1.
*
CDEN = SA
CNUM = ONE
*
10 CONTINUE
CDEN1 = CDEN*SMLNUM
CNUM1 = CNUM / BIGNUM
IF( ABS( CDEN1 ).GT.ABS( CNUM ) .AND. CNUM.NE.ZERO ) THEN
*
* Pre-multiply X by SMLNUM if CDEN is large compared to CNUM.
*
MUL = SMLNUM
DONE = .FALSE.
CDEN = CDEN1
ELSE IF( ABS( CNUM1 ).GT.ABS( CDEN ) ) THEN
*
* Pre-multiply X by BIGNUM if CDEN is small compared to CNUM.
*
MUL = BIGNUM
DONE = .FALSE.
CNUM = CNUM1
ELSE
*
* Multiply X by CNUM / CDEN and return.
*
MUL = CNUM / CDEN
DONE = .TRUE.
END IF
*
* Scale the vector X by MUL
*
CALL ZDSCAL( N, MUL, SX, INCX )
*
IF( .NOT.DONE )
$ GO TO 10
*
RETURN
*
* End of ZDRSCL
*
END
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