Chandrupatla                          APS  solved    CHA  solved   both
ours @ xtol (as benchmarked)         2785  153/154   2424   40/45   5209
ours @ xtol/2 (ITP's correction)     2787  153/154   2441   40/45   5228
scipy @ xtol                         2787  153/154   2441   40/45   5228
best_of, as benchmarked              2785  153/154   2423   40/45   5208
best_of, corrected                   2787  153/154   2441   40/45   5228

our implementation, largest final bracket width / xtol over all problems: 1000000000000.000
(everyone else stops at <= 1; a value up to 2 confirms the looser rule)