You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
139 lines
3.3 KiB
139 lines
3.3 KiB
2 years ago
|
*> \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.
|
||
|
|
*
|
||
|
|
*> \ingroup complexOTHERauxiliary
|
||
|
|
*
|
||
|
|
*> \par Contributors:
|
||
|
|
* ==================
|
||
|
|
*>
|
||
|
|
*> Nick Higham for use with ZLACON.
|
||
|
|
*
|
||
|
|
* =====================================================================
|
||
|
|
INTEGER FUNCTION IZMAX1( N, ZX, INCX )
|
||
|
|
*
|
||
|
|
* -- LAPACK auxiliary routine --
|
||
|
|
* -- LAPACK is a software package provided by Univ. of Tennessee, --
|
||
|
|
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
|
||
|
|
*
|
||
|
|
* .. 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
|