On 23 Dec 2020, at 13:30, Roland Haas <rhaas@illinois.edu> wrote:

Hello Karima,

I am not a black hole evolution expert, but I can give this a try.

Hi,

I use the parameter

TwoPunctures::TP_epsilon =
1e-6

to ensure that the NaN never appears, no matter where I place the BHs. This replaces a denominator

sqrt (pow (r2_plus,
2))

with

sqrt (pow (r2_plus,
2) + 
pow (TP_epsilon, 
4))

See

so adds a fixed source of error to your evolution, but the effect of this is negligible.