text:       Subroutine dft_gather(n,a,b,index,idiff)
  
  C$Id$
        implicit none
        
        integer n
        double precision a(n),b(*)
        integer index(n),idiff
        integer i
  
  c****************************************************************************
  
        do 10 i = 1,n
         a(i) = b(index(i)-idiff)
     10 continue
  
        end
  