Implementation is more important than ideas.

Beautiful

The fix was to be smarter about avoiding this extra bookkeeping in cases that we can determine it won't be used.

We recently added some extra bookkeeping that's designed to make higher order derivatives faster. However, in this graph, which evaluates a first derivative at many many different points, the calculator was spending all its time on this new bookkeeping.

This should be fixed now. Thank you for reporting!