function A = randAth(n,th0)
while 1
  A = pnormdim(rand(n),1);
  if getTH(A) <= th0
    return
  end
end
return


function h = getTH(A)
[n,n] = size(A);
h = 0;
for i=1:n
  for j=i+1:n
    x = A(:,i);
    y = A(:,j);
    d = TV(x-y);
    h = max(h,d);
  end
end
return