function optedo2(alpha,n,m)
B= n*n*(sparse(3:n,1:n-2,1,n,n)+sparse(2:n,1:n-1,-2,n,n)+sparse(1:n,1:n,1,n,n));
B(1,1)=n*n*2;
matobs = zeros(n,n);
for i=1:m
  index=int8((i-0.5)/m*(n+1));
  matobs(index,index)=1.;
end
mat=matobs+alpha*B'*B;
xobs=sparse(n,1);
for i=1:n
  xobs(i)=1+0.1*cos(10*pi*i/n);
end
rhs=matobs*xobs;
x=mat\rhs;
q=B*x;
figure(1);plot(x,'o');
hold on;
plot(xobs,'+');
figure(2);plot(q,'x');
norm(matobs*(x-xobs))
norm(q)
return
