On a similar note, I also though that rejecting some results from the matrix might simplify the possible connections when solving the Travelling Salesman Problem.
Unsure if JSprit automatically rejects these but I thought might as well reject it before hand.
This was a semi recent attempt,
For 1021 delivery points;
Total connections 1021*1021 = 1,042,441
Execution time in seconds : 443.59357
Used < 150m : 37,686
Used >= 150m, < 200m : 19,014
Used >= 200m, < 250m : 24,022
Used >= 250m, < 300m : 28,406
Rejected >= 300m : 933,313
My points are quite clustered and I wouldn’t expect to use any returned distances =>300m from graphhopper.