<div dir="ltr">On Thu, Nov 19, 2015 at 11:05 PM, Frank Loeffler <span dir="ltr"><<a href="mailto:knarf@cct.lsu.edu" target="_blank">knarf@cct.lsu.edu</a>></span> wrote:<br><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On Fri, Nov 20, 2015 at 04:41:48AM +0000, Garrison, David wrote:<br>
> How do you find the number of non-zero elements in a Grid Function in Cactus?<br>
<br>
</span>The best way would probably be to count them locally on each process,<br>
write the result in a distributed grid array, and do the sum there by<br>
syncing the array and counting locally (not sure if a reduction on such<br>
an array would work, it might).<br></blockquote><div><br></div><div>There is no need for a distributed grid array. After counting locally, a "local reduction" (i.e. reduction of a local variable) gives you the overall result.</div><div><br></div><div>-erik</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Another, but more expensive way (in terms of memory size and memory<br>
accesses) would be to create another grid function, populate it with<br>
either 1 or 0 depending on the non-zero-property of the GF you are<br>
interested in, and calling the existing sum-reduction on it.<br>
<span class="HOEnZb"><font color="#888888"><br>
Frank<br>
<br>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature">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>
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