izmax1.f

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*> \brief \b IZMAX1 finds the index of the vector element whose real part has maximum absolute value.
*
*  =========== DOCUMENTATION ===========
*
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*            http://www.netlib.org/lapack/explore-html/ 
*
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*
*  Definition:
*  ===========
*
*       INTEGER          FUNCTION IZMAX1( N, CX, INCX )
* 
*       .. Scalar Arguments ..
*       INTEGER            INCX, N
*       ..
*       .. Array Arguments ..
*       COMPLEX*16         CX( * )
*       ..
*  
*
*> \par 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.
*> \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 September 2012
*
*> \ingroup complex16OTHERauxiliary
*
*> \par Contributors:
*  ==================
*>
*> Nick Higham for use with ZLACON.
*
*  =====================================================================
      INTEGER          FUNCTION izmax1( N, CX, INCX )
*
*  -- LAPACK auxiliary routine (version 3.4.2) --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     September 2012
*
*     .. 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