I have a question somewhat unrelated to the previous discussion.
What is a good way to specify relative tolerance in the case where the exact value of the integral is close to zero?
I’ve looked at QuadGK internals and there the relative error is calculated by dividing sum of errors over the sum of integrals over segments. In the case of almost zero-valued integral, I could think about calculating the sum of absolute values of integrals over segments and then divide total error by this new sum.
What do you think of such an approach?