BUG: gambit-enumpoly missing an equilibrium for 2x2x2.nfg on some platforms

[tturocy]

On my M2 pro 2023 mac mini, gambit-enumpoly only returns 8 equilibria for 2x2x2.nfg:

build/gambit-enumpoly -V contrib/games/2x2x2.nfg
Compute Nash equilibria by solving polynomial systems
Gambit version 16.2.0, Copyright (C) 1994-2024, The Gambit Project
This is free software, distributed under the GNU GPL

candidate,10,10,10
NE,1.000000,0.000000,1.000000,0.000000,1.000000,0.000000
candidate,10,01,01
NE,1.000000,0.000000,0.000000,1.000000,0.000000,1.000000
candidate,01,10,01
NE,0.000000,1.000000,1.000000,0.000000,0.000000,1.000000
candidate,01,01,10
NE,0.000000,1.000000,0.000000,1.000000,1.000000,0.000000
candidate,11,11,10
NE,0.500000,0.500000,0.500000,0.500000,1.000000,0.000000
candidate,11,11,01
candidate,11,10,11
NE,0.333333,0.666667,1.000000,0.000000,0.250000,0.750000
candidate,11,01,11
candidate,10,11,11
candidate,01,11,11
NE,0.000000,1.000000,0.250000,0.750000,0.333333,0.666667
candidate,11,11,11
NE,0.400000,0.600000,0.500000,0.500000,0.333333,0.666667

There are two equilibria with full support. However, on my older MacBook Pro (2017, Intel Core i5), I get the correct output, with two equilibria with full support.

This discrepancy appears to date back quite some time.

Preliminary speculation is that this will have to do with tolerances, as previously in the development of gambit-enumpoly we noted some irregularities with how tolerances were operating.