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*> \brief \b IZMAX1
*
* =========== 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, CX, INCX )
*
* .. Scalar Arguments ..
* INTEGER INCX, N
* ..
* .. Array Arguments ..
* COMPLEX*16 CX( * )
* ..
*
* Purpose
* =======
*
*>\details \b Purpose:
*>\verbatim
*>
*> IZMAX1 finds the index of the element whose real part has maximum
*> absolute value.
*>
*> Based on IZAMAX from Level 1 BLAS.
*> The change is to use the 'genuine' absolute value.
*>
*> Contributed by Nick Higham for use with ZLACON.
*>
*>\endverbatim
*
* Arguments
* =========
*
*> \param[in] N
*> \verbatim
*> N is INTEGER
*> The number of elements in the vector CX.
*> \endverbatim
*>
*> \param[in] CX
*> \verbatim
*> CX is COMPLEX*16 array, dimension (N)
*> The vector whose elements will be summed.
*> \endverbatim
*>
*> \param[in] INCX
*> \verbatim
*> INCX is INTEGER
*> The spacing between successive values of CX. INCX >= 1.
*> \endverbatim
*>
*
* Authors
* =======
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date November 2011
*
*> \ingroup complex16OTHERauxiliary
*
* =====================================================================
INTEGER FUNCTION IZMAX1( N, CX, INCX )
*
* -- LAPACK auxiliary routine (version 3.2) --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* November 2011
*
* .. Scalar Arguments ..
INTEGER INCX, N
* ..
* .. Array Arguments ..
COMPLEX*16 CX( * )
* ..
*
* =====================================================================
*
* .. Local Scalars ..
INTEGER I, IX
DOUBLE PRECISION SMAX
COMPLEX*16 ZDUM
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS
* ..
* .. Statement Functions ..
DOUBLE PRECISION CABS1
* ..
* .. Statement Function definitions ..
*
* NEXT LINE IS THE ONLY MODIFICATION.
CABS1( ZDUM ) = ABS( ZDUM )
* ..
* .. Executable Statements ..
*
IZMAX1 = 0
IF( N.LT.1 )
$ RETURN
IZMAX1 = 1
IF( N.EQ.1 )
$ RETURN
IF( INCX.EQ.1 )
$ GO TO 30
*
* CODE FOR INCREMENT NOT EQUAL TO 1
*
IX = 1
SMAX = CABS1( CX( 1 ) )
IX = IX + INCX
DO 20 I = 2, N
IF( CABS1( CX( IX ) ).LE.SMAX )
$ GO TO 10
IZMAX1 = I
SMAX = CABS1( CX( IX ) )
10 CONTINUE
IX = IX + INCX
20 CONTINUE
RETURN
*
* CODE FOR INCREMENT EQUAL TO 1
*
30 CONTINUE
SMAX = CABS1( CX( 1 ) )
DO 40 I = 2, N
IF( CABS1( CX( I ) ).LE.SMAX )
$ GO TO 40
IZMAX1 = I
SMAX = CABS1( CX( I ) )
40 CONTINUE
RETURN
*
* End of IZMAX1
*
END
|
