function K = evaluate(ker, x1, x2)



n = size(x2,1);
m = size(x1,1);
K = zeros(m,n);

if (m <= n)
   for p = 1:m
      K(p,:) = sum((ones(n,1)*x1(p,:) - x2).^2,2).';
   end
else
   for p = 1:n
      K(:,p) = sum((x1 - ones(m,1)*x2(p,:)).^2,2);
   end
end

K = exp(-ker.gamma*K);