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<p>Present: Liu Haoyang, Zhao Zhi-Chao, Bill Gabella, Zach Etienne, Steve Brandt, Roland Haas<br>
</p>
<p>Chair: Steve<br>
Minutes: Bill</p>
<p>* ETK Workshop at LSU in August 2020. <br>
o Likely August 3-7, the first week. Let Steve know what you would like to see there. Planning on student tutorial, will have students from LSU.
<br>
o Some money for travel support---if you have a student you want to send ask Steve.
<br>
o NRPy tutorial would be nice---Zach agrees. NRPy spreading around China; Zach back from a recent visit there.<br>
</p>
<p>* Any information about an ETK workshop in Europe? Need to know and coordinate schedules.</p>
<p>* Working group update: Performance Optimization AMRex<br>
</p>
<p>o AMRex work with Erik and Steve. AMRex is a mesh refinement<b> </b>library developed by the DoE specifically by LBNL in California. Built-in support
<br>
for tiling and multi-threading. Erik, Steve, and Roland, try to use AMRex as an underlying driver for Cactus. Have wave equation working. Roland<br>
visited Erik for a week over break, mesh-refinement code in there, and Zach's Baikal BSSN code that can evolve Minkowski ST without failing.<br>
And can do Schwarzschild BH with two puncture, until it fails. Likely the boundary conditions are wrong. Using two punctures as initial data.
<br>
Is a Cactus thorn. Looping over grid points is different, so not backward compatible. Developed as a hydro code. Supports two kinds of variables,<br>
cell-centered and vertex-centered, which is not supported in Cactus at all. Metric is vertex-centered. AMRex uses the PreSync infrastructure of
<br>
the Cactus branch Steve has been working on. Code is public. Repo cactusamrex in Erik's account (see below). Is the docker file Erik uses for<br>
testing. Need latest version of cmake. Erik is working on BCs other than periodic, Dirichlet and Reflection.<b> </b> Is a work in progress, but at a point<br>
where we can take Minkowski or Schwarzschild ST and run on a cluster and see how the framework scales---effects on run speed, etc. All<br>
refinements are on the same time step.</p>
<p>o For Minkowski ST when evolve quantities 0 or 1 at least it does not die, but not sure if it is still 0 or 1, responding to Steve's question.<br>
o Took Zach's notebook and re-wrote the glue for it to work. Kept the physics the same.<br>
o Links:<br>
<a href="https://amrex-codes.github.io/">https://bitbucket.org/eschnett/cactusamrex/src/master/<br>
https://amrex-codes.github.io/</a><br>
o Zach suggested a trumpet BH solution with corresponding gauge conditions, guaranteed to be static ST, and is a good test. Also numerically<br>
stable; shows up in the original NRPy paper.<br>
</p>
<p>* Steve wants to get rid of cactuscode.org and make it a web page on ETK website. Should have an example web page for next week.</p>
<p>* Next release, 6 months from late October, so maybe April. <br>
o Volunteer for heading the release needs to be determined.<br>
</p>
<p>* Roland has some bug fixes to back port to the release. <br>
o System topology thorn will fail if using new (2.X) of hwloc library. Small change to the search.
<br>
o In the ticketing system with "backports" in the subject. He would like to do this. Steve will look at the tickets and commits.
<br>
<font size="+1"><span style="color: rgb(0, 0, 0); font-family:
"Times New Roman"; font-size: medium; font-style:
normal; font-variant-ligatures: normal; font-variant-caps:
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2; text-align: start; text-indent: 0px; text-transform:
none; white-space: normal; widows: 2; word-spacing: 0px;
-webkit-text-stroke-width: 0px; text-decoration-style:
initial; text-decoration-color: initial; display: inline
!important; float: none;"><span></span></span><a href="https://bitbucket.org/einsteintoolkit/tickets/issues/2314/" style="color: rgb(0, 0, 128); text-decoration: underline;
font-family: "Times New Roman"; font-size: medium;
font-style: normal; font-variant-ligatures: normal;
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normal; orphans: 2; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: 2;
word-spacing: 0px; -webkit-text-stroke-width: 0px;">https://bitbucket.org/einsteintoolkit/tickets/issues/2314/</a></font><br>
o Maybe some updates for simfactory machines, but those get updated all the time.</p>
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[edited for readability-my paragraph (non)wrapping looked like hell on lists.einsteintoolkit.org, finally put in hard breaks with shift-return<br>
in Thunderbird, bill]<br>
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