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<div class="">On 23 Dec 2020, at 13:30, Roland Haas <<a href="mailto:rhaas@illinois.edu" class="">rhaas@illinois.edu</a>> wrote:</div>
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<div class="">Hello Karima,<br class="">
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I am not a black hole evolution expert, but I can give this a try.<br class="">
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<div>Hi,</div>
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<div>I use the parameter</div>
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<span style="color: rgb(32, 32, 32);" class="">TwoPunctures</span>::<span style="color: rgb(32, 32, 32);" class="">TP_epsilon</span> =
<span style="color: rgb(101, 84, 192);" class="">1e-6</span></div>
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<div>to ensure that the NaN never appears, no matter where I place the BHs. This replaces a denominator</div>
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<span style="color: rgb(32, 32, 32);" class="">sqrt</span> (<span style="color: rgb(32, 32, 32);" class="">pow</span> (<span style="color: rgb(32, 32, 32);" class="">r2_plus</span>,
<span style="color: rgb(101, 84, 192);" class="">2</span>))</div>
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<div style="font-family: Helvetica; font-size: 12px; white-space: normal;">with</div>
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<div style="line-height: 20px;" class=""><span style="color: rgb(32, 32, 32);" class="">sqrt</span> (<span style="color: rgb(32, 32, 32);" class="">pow</span> (<span style="color: rgb(32, 32, 32);" class="">r2_plus</span>,
<span style="color: rgb(101, 84, 192);" class="">2</span>) + <span style="color: rgb(32, 32, 32);" class="">
pow</span> (<span style="color: rgb(32, 32, 32);" class="">TP_epsilon</span>, <span style="color: rgb(101, 84, 192);" class="">
4</span>))</div>
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<div>See</div>
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<div><a href="https://bitbucket.org/einsteintoolkit/einsteininitialdata/src/master/TwoPunctures/src/Equations.c#lines-91" class="">https://bitbucket.org/einsteintoolkit/einsteininitialdata/src/master/TwoPunctures/src/Equations.c#lines-91</a></div>
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<div>so adds a fixed source of error to your evolution, but the effect of this is negligible.</div>
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-- <br class="">
Ian<b class=""><span class="Apple-converted-space"> </span></b>Hinder<br class="">
Research Software Engineer<br class="">
University of Manchester, UK</div>
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