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*> \brief \b IZMAX1 finds the index of the first vector element of maximum absolute value.
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
*> Download IZMAX1 + dependencies
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/izmax1.f">
*> [TGZ]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/izmax1.f">
*> [ZIP]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/izmax1.f">
*> [TXT]</a>
*> \endhtmlonly
*
* Definition:
* ===========
*
* INTEGER FUNCTION IZMAX1( N, ZX, INCX )
*
* .. Scalar Arguments ..
* INTEGER INCX, N
* ..
* .. Array Arguments ..
* COMPLEX*16 ZX( * )
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> IZMAX1 finds the index of the first vector element of maximum absolute value.
*>
*> Based on IZAMAX from Level 1 BLAS.
*> The change is to use the 'genuine' absolute value.
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in] N
*> \verbatim
*> N is INTEGER
*> The number of elements in the vector ZX.
*> \endverbatim
*>
*> \param[in] ZX
*> \verbatim
*> ZX is COMPLEX*16 array, dimension (N)
*> The vector ZX. The IZMAX1 function returns the index of its first
*> element of maximum absolute value.
*> \endverbatim
*>
*> \param[in] INCX
*> \verbatim
*> INCX is INTEGER
*> The spacing between successive values of ZX. INCX >= 1.
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date February 2014
*
*> \ingroup complexOTHERauxiliary
*
*> \par Contributors:
* ==================
*>
*> Nick Higham for use with ZLACON.
*
* =====================================================================
INTEGER FUNCTION IZMAX1( N, ZX, INCX )
*
* -- LAPACK auxiliary 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..--
* February 2014
*
* .. Scalar Arguments ..
INTEGER INCX, N
* ..
* .. Array Arguments ..
COMPLEX*16 ZX(*)
* ..
*
* =====================================================================
*
* .. Local Scalars ..
DOUBLE PRECISION DMAX
INTEGER I, IX
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS
* ..
* .. Executable Statements ..
*
IZMAX1 = 0
IF (N.LT.1 .OR. INCX.LE.0) RETURN
IZMAX1 = 1
IF (N.EQ.1) RETURN
IF (INCX.EQ.1) THEN
*
* code for increment equal to 1
*
DMAX = ABS(ZX(1))
DO I = 2,N
IF (ABS(ZX(I)).GT.DMAX) THEN
IZMAX1 = I
DMAX = ABS(ZX(I))
END IF
END DO
ELSE
*
* code for increment not equal to 1
*
IX = 1
DMAX = ABS(ZX(1))
IX = IX + INCX
DO I = 2,N
IF (ABS(ZX(IX)).GT.DMAX) THEN
IZMAX1 = I
DMAX = ABS(ZX(IX))
END IF
IX = IX + INCX
END DO
END IF
RETURN
*
* End of IZMAX1
*
END
|
