Implementation doubt

[next-josealbertoarcos]

Hello, and thank you for this wonderful R package.

There's something about this implementation I don't understand. If the goal in Zhou's paper is to minimize this:

Then why is it that in the R package implementation the convergence condition is as follows?

while (iter < maxIter & diff > tol){
  ...
  diff = std::abs(obj_prev - obj);
  ...
}

What I do not understand is the use of the absolute value when calculating the difference. Why do you allow the objective metric to grow? Shouldn't that absolute value be removed?