function test_xa(M,X,alpha,b0,TT,lam)

X0 = simple_paths(M);

RR = {};
for i=1:length(X0)
  RR{i} = spath2cell(M,X0{i});
end

PROGstart(TT,'sparse testing');
for t=1:TT
  for i=1:length(X0)
    x = sample_from_sp(RR{i},lam);
    %fprintf('x = %s\n',x);
    y = b2y(run_dfsa(M,x));
    y_hat = compute_yhat_c(X,{x},alpha,b0,@ptkermx);
    if y~=y_hat
       save PTFAIL M X alpha b0
       'bad'
       keyboard
    end
  end
  PROGupdate(t);
end
PROGend;

return