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*> \brief \b IZAMAX
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition:
* ===========
*
* INTEGER FUNCTION IZAMAX(N,ZX,INCX)
*
* .. Scalar Arguments ..
* INTEGER INCX,N
* ..
* .. Array Arguments ..
* COMPLEX*16 ZX(*)
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> IZAMAX finds the index of the first element having maximum |Re(.)| + |Im(.)|
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date December 2016
*
*> \ingroup aux_blas
*
*> \par Further Details:
* =====================
*>
*> \verbatim
*>
*> jack dongarra, 1/15/85.
*> modified 3/93 to return if incx .le. 0.
*> modified 12/3/93, array(1) declarations changed to array(*)
*> \endverbatim
*>
* =====================================================================
INTEGER FUNCTION IZAMAX(N,ZX,INCX)
*
* -- Reference BLAS level1 routine (version 3.7.0) --
* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* December 2016
*
* .. Scalar Arguments ..
INTEGER INCX,N
* ..
* .. Array Arguments ..
COMPLEX*16 ZX(*)
* ..
*
* =====================================================================
*
* .. Local Scalars ..
DOUBLE PRECISION DMAX
INTEGER I,IX
* ..
* .. External Functions ..
DOUBLE PRECISION DCABS1
EXTERNAL DCABS1
* ..
IZAMAX = 0
IF (N.LT.1 .OR. INCX.LE.0) RETURN
IZAMAX = 1
IF (N.EQ.1) RETURN
IF (INCX.EQ.1) THEN
*
* code for increment equal to 1
*
DMAX = DCABS1(ZX(1))
DO I = 2,N
IF (DCABS1(ZX(I)).GT.DMAX) THEN
IZAMAX = I
DMAX = DCABS1(ZX(I))
END IF
END DO
ELSE
*
* code for increment not equal to 1
*
IX = 1
DMAX = DCABS1(ZX(1))
IX = IX + INCX
DO I = 2,N
IF (DCABS1(ZX(IX)).GT.DMAX) THEN
IZAMAX = I
DMAX = DCABS1(ZX(IX))
END IF
IX = IX + INCX
END DO
END IF
RETURN
END
|
