This is from patch D11432 from Erik Abrahamsson. He found that
in some mpq3 functions called frequently from loops, passing in
buffers for termporary mpq3 values can save substantial time.
On my machine, his example in that patch went from 9.48s to 7.50s
for the boolean part of the calculation. On his machine, a running
time went from 17s to 10.3s.
This is for design task T67744, Boolean Redesign.
It adds a choice of solver to the Boolean modifier and the
Intersect (Boolean) and Intersect (Knife) tools.
The 'Fast' choice is the current Bmesh boolean.
The new 'Exact' choice is a more advanced algorithm that supports
overlapping geometry and uses more robust calculations, but is
slower than the Fast choice.
The default with this commit is set to 'Exact'. We can decide before
the 2.91 release whether or not this is the right choice, but this
choice now will get us more testing and feedback on the new code.
