function vnew=vcycle2(vold,f,nu1,nu2)
% VCYCLE2 V-cycle from page 41 for the Helmoltz equation
global sigma 
lmin=3;
vtmp=vold;
nt=length(f); l=log2(nt-1);
for ij=1:nu1
	vtmp=dampj(vtmp,f);
end
if l > lmin
	nt=length(vtmp); nl=nt-1; h=1/nl; hm2=nl*nl;
	av=zeros(nt,1);
	av(2:nt-1)=-vtmp(1:nt-2)+(2+sigma*h*h)*vtmp(2:nt-1)-vtmp(3:nt);
	r=f-hm2*av;
	fc=ftoc(r); nc=length(fc); vc=zeros(nc,1);
	vc=vcycle2(vc,fc,nu1,nu2);
	vtmp=vtmp+ctof(vc);
end
for ij=1:nu2
	vtmp=dampj(vtmp,f);
end
vnew=vtmp;