icamax Function

public pure function icamax(n, cx, incx)

NAME

icamax(3f) -- [BLAS:AUX_BLAS] Return index of maximum "absolute value" in CX.

SYNOPSIS

 integer function icamax(n,cx,incx)

   .. scalar arguments ..
   integer,intent(in) :: incx,n
   ..
   .. array arguments ..
   complex,intent(in) :: cx(*)
   ..

DEFINITION

 ICAMAX finds the index of the first element having maximum |Re(.)| + |Im(.)|

OPTIONS

N

       N is INTEGER
      number of elements in input vector(s)

CX

       CX is COMPLEX array, dimension ( 1 + ( N - 1 )*abs( INCX ) )

INCX

       INCX is INTEGER
      storage spacing between elements of CX

AUTHORS

  • Univ. of Tennessee
  • Univ. of California Berkeley
  • Univ. of Colorado Denver
  • NAG Ltd.

date:November 2017

FURTHER DETAILS

  jack dongarra, linpack, 3/11/78.
  modified 3/93 to return if incx .le. 0.
  modified 12/3/93, array(1) declarations changed to array(*)

SEE ALSO

Online html documentation available at
http://www.netlib.org/lapack/explore-html/

Arguments

Type IntentOptional Attributes Name
integer, intent(in) :: n
complex, intent(in) :: cx(*)
integer, intent(in) :: incx

Return Value integer


Contents

Variables

Source Code

icamax

Variables

Type Visibility Attributes Name Initial
integer, public :: i
integer, public :: ix
real, public :: smax

Source Code

pure integer function icamax(n,cx,incx)
      implicit none
!
!  -- Reference BLAS level1 routine (version 3.8.0) --
!  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
!  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
!     November 2017
!
!     .. Scalar Arguments ..
      integer,intent(in) :: incx,n
!     ..
!     .. Array Arguments ..
      complex,intent(in) :: cx(*)
!     ..
!  =====================================================================
!     .. Local Scalars ..
      real smax
      integer i,ix
!     ..
!     .. External Functions ..  REAL SCABS1
!     ..
      icamax = 0
      if (n.lt.1 .or. incx.le.0) return
      icamax = 1
      if (n.eq.1) return
      if (incx.eq.1) then
!
!        code for increment equal to 1
!
         smax = scabs1(cx(1))
         do i = 2,n
            if (scabs1(cx(i)).gt.smax) then
               icamax = i
               smax = scabs1(cx(i))
            endif
         enddo
      else
!
!        code for increment not equal to 1
!
         ix = 1
         smax = scabs1(cx(1))
         ix = ix + incx
         do i = 2,n
            if (scabs1(cx(ix)).gt.smax) then
               icamax = i
               smax = scabs1(cx(ix))
            endif
            ix = ix + incx
         enddo
      endif
end function icamax