function z = bumps ( x, y )

%% BUMPS evaluates a function z(x,y) that has a bump up and one down.
%
%  X, Y, are the evaluation point.  X and Y can be vectors or arrays.
%
%  Z is the function value at (X,Y).
%
  z = 2.0 ./ exp ( ( x - 0.5 ).^2 + y.^2 ) ...
    - 2.0 ./ exp ( ( x + 0.5 ).^2 + y.^2 );

  return
end

