<div><div dir="auto">It is supposed to be negative at lower boundaries. Sign error?</div></div><div dir="auto"><br></div><div dir="auto">-erik</div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, May 7, 2020 at 02:42 Roland Haas <<a href="mailto:rhaas@illinois.edu">rhaas@illinois.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hello all,<br>
<br>
I am trying to loop over the boundary of my domain using<br>
CCTK_LOOP3_BND(cckGH, i,j,k, ni,nj,nk). The documentation<br>
<a href="http://einsteintoolkit.org/usersguide/UsersGuidech9.html#x13-102000C1.7.1" rel="noreferrer" target="_blank">http://einsteintoolkit.org/usersguide/UsersGuidech9.html#x13-102000C1.7.1</a><br>
says that "ni, nj, and nk are names of variables describing the<br>
(outwards pointing) normal direction to the boundary as well as the<br>
distance to the boundary."<br>
<br>
However on a 5x5x5 grid and 1 boundary point in a uniprocess setup ni,<br>
nj, nk are either 0 or 1 but never eg -1 which I would expect for the<br>
lower boundary.<br>
<br>
Looking at the code in flesh/src/include/cctk_Loop.h shows that ni is<br>
computed as <br>
<br>
const int ni CCTK_ATTRIBUTE_UNUSED = cctki0_idir<0 ? i+1 : cctki0_idir==0 ? 0 : cctki0_imax-i;<br>
<br>
ie by construction is always non-negative. LoopControl does the same.<br>
<br>
Now my question is how am I supposed to find out which boundary I am<br>
at (lower or upper)?<br>
<br>
Yours,<br>
Roland<br>
<br>
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</blockquote></div></div>-- <br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div>Erik Schnetter <<a href="mailto:schnetter@cct.lsu.edu" target="_blank">schnetter@cct.lsu.edu</a>><br><a href="http://www.perimeterinstitute.ca/personal/eschnetter/" target="_blank">http://www.perimeterinstitute.ca/personal/eschnetter/</a></div><div><br></div></div></div>