redblack5.f

LPARX is a C++ class library for for implementing portable scientific applications on distributed me

	subroutine redblack5(U, nl, nh, h, offset, r)
	integer nl(0:1), nh(0:1), offset
	double precision U(nl(0)-1:nh(0)+1, nl(1)-1:nh(1)+1), h, r

	double precision r, Au
	integer i, j, is

	r = 0.0d0

	do 1000 j = nl(1), nh(1)
	   is = mod(j+offset, 2)
	   do 2000 i = nl(0)+is, nh(0), 2
              Au = (U(i-1,j)+U(i+1,j)+U(i,j-1)+U(i,j+1))/4.0
	      r = max(r, dabs(Au-U(i,j)))
	      U(i,j) = Au
2000	   continue
1000	continue

	return
	end