c	***********************************************************************
	subroutine invdiag(a,b,n)
c	inverse of a diagonal matrix 
c       jul 2011 malv
c	***********************************************************************
	implicit none

	integer n,i,j,k
	real*8 a(n,n),b(n,n)

	do 1,i=2,n-1
	  do 2,j=2,n-1
	    if (i.eq.j) then
              a(i,j) = 1.d0/b(i,i)
	    else
	      a(i,j)=0.0d0
	    end if
 2	  continue
 1	continue
	do k=1,n
	  a(n,k) = 0.0d0
	  a(1,k) = 0.0d0
	  a(k,1) = 0.0d0
	  a(k,n) = 0.0d0
	end do
	return
	end