<html>#2288: Lean's boundary condition setting for BSSN constraints only fills in a single ghostzone
<table style='border-spacing: 1ex 0pt; '>
<tr><td style='text-align:right'> Reporter:</td><td>Zach Etienne</td></tr>
<tr><td style='text-align:right'> Status:</td><td>open</td></tr>
<tr><td style='text-align:right'>Milestone:</td><td></td></tr>
<tr><td style='text-align:right'> Version:</td><td></td></tr>
<tr><td style='text-align:right'> Type:</td><td>bug</td></tr>
<tr><td style='text-align:right'> Priority:</td><td>major</td></tr>
<tr><td style='text-align:right'>Component:</td><td>EinsteinToolkit thorn</td></tr>
</table>
<p>Comment (by Roland Haas):</p>
<p>Calling <code>GetBoundarySpecification</code> in Llama code will give you incorrect answers / will fail. The function is provided by the thorn <code>CoordBase</code> which may not be active at all for a Llama run. if it is active the it will report its ow parameter settings and not <code>Coordinates</code>' (the Llama equivalent thorn to <code>CoordBase</code>).</p>
<p>How to handle this in the developer’s branch is mostly up to you. You could give my proposed solution a try, you could also try and schedule the <code>SelectBCs</code> function as <code>SINGLEMAP</code> then call <code>MultiPatch_GetBoundarySpecifiction</code> and select boundary conditions on only those faces that <code>is_internal</code> is 0.Note that, while this would let you have different boundary widths for different boundary faces, you still cannot have the same face be a boundary on different maps and have different options (eg have 3 point wide boundary in “z” on map 1 but a 1 point wide boundary in “z” on map 2) due to the way the <code>Boundary</code> thorn’s <code>ApplyBCs</code> group works. None of the current Llama setups requires this though. Eg for the, almost exclusively used, 7patch system the outer boundaries are all on maps 1-6 (the cubed spheres) and they all have the only outer boundary face being in direction of positive third coordinat
e (“radial”). Ie the coordinate setup is such that having a single “face” be selected for the outer boundary on all maps and that not eg the “radial” direction is a different coordinate number on the different maps.</p>
<p>In Lean_public’s case backporting this into the release branch is not really required (though you can if you want to) since, different from Baikal, the current released code does not prevent you from running in certain situations and does give correct results (I think) when using the typical radiation boundary condition (same as McLachlan).</p>
<p>--<br/>
Ticket URL: <a href='https://bitbucket.org/einsteintoolkit/tickets/issues/2288/leans-boundary-condition-setting-for-bssn'>https://bitbucket.org/einsteintoolkit/tickets/issues/2288/leans-boundary-condition-setting-for-bssn</a></p>
</html>