Well, my point is that it's not as easy as saying "just pick a smarter algorithm". Not all problems needing high precision can resort to a smart summation. Some

Well, my point is that it's not as easy as saying "just pick a smarter algorithm". Not all problems needing high precision can resort to a smart summation. Sometimes that smart algorithm just doesn't exist yet. You are also right, that if you can solve your problem with high precision, it's unlikely that just quad precision will be enough. For example the inverse Laplace transform. In some cases you need thousands of digits. The cases where double precision is not enough, but quad precision is are probably rare. But it's worth a try.