[Users] Meeting Minutes for 2020-01-09

Haas, Roland rhaas at illinois.edu
Thu Jan 9 11:33:28 CST 2020

Hello all,

while I was not in time to actually prepare these before the call, this:


are some slides outlining the current CarpetX status.


> Present: Liu Haoyang, Zhao Zhi-Chao, Bill Gabella, Zach Etienne,  Steve Brandt, Roland Haas
> Chair: Steve
> Minutes: Bill
> * ETK Workshop at LSU in August 2020.
> 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.
> o Some money for travel support---if you have a student you want to send ask Steve.
> o NRPy tutorial would be nice---Zach agrees.  NRPy spreading around China; Zach back from a recent visit there.
> * Any information about an ETK workshop in Europe?  Need to know and coordinate schedules.
> * Working group update: Performance Optimization    AMRex
> o AMRex work with Erik and Steve.  AMRex is a mesh refinement library developed by the DoE specifically by LBNL in California.  Built-in support
> for tiling and multi-threading.  Erik, Steve, and Roland, try to use AMRex as an underlying driver for Cactus.  Have wave equation working.  Roland
> 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.
> And can do Schwarzschild BH with two puncture, until it fails.  Likely the boundary conditions are wrong.  Using two punctures as initial data.
> Is a Cactus thorn.  Looping over grid points is different, so not backward compatible.  Developed as a hydro code.  Supports two kinds of variables,
> cell-centered and vertex-centered, which is not supported in Cactus at all.  Metric is vertex-centered.  AMRex uses the PreSync infrastructure of
> 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
> testing.  Need latest version of cmake.  Erik is working on BCs other than periodic, Dirichlet and Reflection.  Is a work in progress, but at a point
> 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
> refinements are on the same time step.
> 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.
> o Took Zach's notebook and re-wrote the glue for it to work.  Kept the physics the same.
> o Links:
> https://bitbucket.org/eschnett/cactusamrex/src/master/
> https://amrex-codes.github.io/<https://amrex-codes.github.io/>
> o Zach suggested a trumpet BH solution with corresponding gauge conditions, guaranteed to be static ST, and is a good test.  Also numerically
> stable; shows up in the original NRPy paper.
> * 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.
> * Next release, 6 months from late October, so maybe April.
> o Volunteer for heading the release needs to be determined.
> * Roland has some bug fixes to back port to the release.
> o System topology thorn will fail if using new (2.X)  of hwloc library.  Small change to the search.
> o In the ticketing system with "backports" in the subject.  He would like to do this.  Steve will look at the tickets and commits.
> https://bitbucket.org/einsteintoolkit/tickets/issues/2314/
> o Maybe some updates for simfactory machines, but those get updated all the time.
> [edited for readability-my paragraph (non)wrapping looked like hell on lists.einsteintoolkit.org, finally put in hard breaks with shift-return
> in Thunderbird, bill]

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