function w=subdomain(rhs,mx,my,h)
%
% SUBDOMAIN is a direct subdomain solver, zero boundary data.
%
% function w=subdomain(rhs,mx,my,h)
%
global lf uf
rl=rhs(:);
w=zeros(mx,my);
%al=pmat2(mx,my,h); ul=al\rl;
ult=lf\rl; ul=uf\ult;
w(:)=ul;