share/colnew/fortran/idamax.f

   1       integer function idamax(n,dx,incx)
   2 c
   3 c     finds the index of element having max. absolute value.
   4 c     jack dongarra, linpack, 3/11/78.
   5 c     modified 3/93 to return if incx .le. 0.
   6 c     modified 12/3/93, array(1) declarations changed to array(*)
   7 c
   8       double precision dx(*),dmax
   9       integer i,incx,ix,n
  10 c
  11       idamax = 0
  12       if( n.lt.1 .or. incx.le.0 ) return
  13       idamax = 1
  14       if(n.eq.1)return
  15       if(incx.eq.1)go to 20
  16 c
  17 c        code for increment not equal to 1
  18 c
  19       ix = 1
  20       dmax = dabs(dx(1))
  21       ix = ix + incx
  22       do 10 i = 2,n
  23          if(dabs(dx(ix)).le.dmax) go to 5
  24          idamax = i
  25          dmax = dabs(dx(ix))
  26     5    ix = ix + incx
  27    10 continue
  28       return
  29 c
  30 c        code for increment equal to 1
  31 c
  32    20 dmax = dabs(dx(1))
  33       do 30 i = 2,n
  34          if(dabs(dx(i)).le.dmax) go to 30
  35          idamax = i
  36          dmax = dabs(dx(i))
  37    30 continue
  38       return
  39       end