142 lines
3.4 KiB
Fortran
142 lines
3.4 KiB
Fortran
*> \brief \b IZMAX1 finds the index of the first vector element of maximum absolute value.
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*
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* =========== DOCUMENTATION ===========
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*
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* Online html documentation available at
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* http://www.netlib.org/lapack/explore-html/
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*
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*> \htmlonly
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*> Download IZMAX1 + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/izmax1.f">
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*> [TGZ]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/izmax1.f">
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*> [ZIP]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/izmax1.f">
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*> [TXT]</a>
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*> \endhtmlonly
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*
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* Definition:
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* ===========
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*
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* INTEGER FUNCTION IZMAX1( N, ZX, INCX )
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*
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* .. Scalar Arguments ..
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* INTEGER INCX, N
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* ..
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* .. Array Arguments ..
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* COMPLEX*16 ZX( * )
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* ..
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*
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*
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*> \par Purpose:
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* =============
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*>
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*> \verbatim
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*>
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*> IZMAX1 finds the index of the first vector element of maximum absolute value.
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*>
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*> Based on IZAMAX from Level 1 BLAS.
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*> The change is to use the 'genuine' absolute value.
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*> \endverbatim
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*
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* Arguments:
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* ==========
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*
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*> \param[in] N
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*> \verbatim
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*> N is INTEGER
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*> The number of elements in the vector ZX.
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*> \endverbatim
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*>
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*> \param[in] ZX
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*> \verbatim
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*> ZX is COMPLEX*16 array, dimension (N)
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*> The vector ZX. The IZMAX1 function returns the index of its first
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*> element of maximum absolute value.
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*> \endverbatim
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*>
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*> \param[in] INCX
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*> \verbatim
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*> INCX is INTEGER
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*> The spacing between successive values of ZX. INCX >= 1.
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*> \endverbatim
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*
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* Authors:
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* ========
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*
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*> \author Univ. of Tennessee
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*> \author Univ. of California Berkeley
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*> \author Univ. of Colorado Denver
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*> \author NAG Ltd.
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*
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*> \date February 2014
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*
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*> \ingroup complexOTHERauxiliary
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*
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*> \par Contributors:
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* ==================
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*>
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*> Nick Higham for use with ZLACON.
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*
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* =====================================================================
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INTEGER FUNCTION IZMAX1( N, ZX, INCX )
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*
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* -- LAPACK auxiliary routine (version 3.6.0) --
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* -- LAPACK is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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* February 2014
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*
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* .. Scalar Arguments ..
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INTEGER INCX, N
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* ..
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* .. Array Arguments ..
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COMPLEX*16 ZX(*)
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* ..
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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DOUBLE PRECISION DMAX
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INTEGER I, IX
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC ABS
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* ..
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* .. Executable Statements ..
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*
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IZMAX1 = 0
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IF (N.LT.1 .OR. INCX.LE.0) RETURN
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IZMAX1 = 1
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IF (N.EQ.1) RETURN
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IF (INCX.EQ.1) THEN
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*
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* code for increment equal to 1
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*
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DMAX = ABS(ZX(1))
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DO I = 2,N
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IF (ABS(ZX(I)).GT.DMAX) THEN
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IZMAX1 = I
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DMAX = ABS(ZX(I))
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END IF
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END DO
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ELSE
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*
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* code for increment not equal to 1
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*
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IX = 1
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DMAX = ABS(ZX(1))
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IX = IX + INCX
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DO I = 2,N
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IF (ABS(ZX(IX)).GT.DMAX) THEN
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IZMAX1 = I
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DMAX = ABS(ZX(IX))
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END IF
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IX = IX + INCX
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END DO
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END IF
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RETURN
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*
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* End of IZMAX1
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*
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END
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