[Users] Meeting Minutes 2020-06-18

Bill Gabella b.gabella at vanderbilt.edu
Thu Jun 18 10:26:23 CDT 2020

Present: Steve B, Bill G, Roland H, Peter D, Peter S, Atul K, Mario GA,
Federico C, Miguel G, Antoni RB, Yosef Z, Liu H, Zach E, Maria H

Chair: Steve
Minutes: Bill

* gcc 10 issues [RH]

  RH, good news collected bits and pieces for compiling on gcc 10 and
gfortran 10 and working on his workstation, patch to flesh, patch to
cactus test
repos, to event horizon finder, patches to GRHydro and XXX due to
inconsistent types, more wrong than before but at least consistent, so
the compiler
is happy, LAPACK to newest version, patch to HDF5 that we check out,
compiles and running the testsuite on many machines.  We can backport these
changes.  This is the most trouble with a new compiler release.  Have
had compilers change on us, like gcc 4 to 5 where inline syntax
changed.  These
seems to be the worst compiler upgrade we have had.

** 2403, https://bitbucket.org/einsteintoolkit/tickets/issues/2403

** also affects CCTK_Reduce subroutines which is already incorrect F77
since they are variadic functions which FORTRAN never supported.  Real world
examples where this fails are known and were reported in 2004,
http://cactuscode.org/pipermail/users/2004-September/001224.html  by
Roberto de Pietri.

** also affects EOS_Omnik, GRHydro [RH]

* reviewers for proposed inclusions [RH]

** ReadInterpolate https://github.com/rhaas80/ReadInterpolate.git thorn
ticket 2416 https://bitbucket.org/einsteintoolkit/tickets/issues/2416  
no reviewer

Takes 3d output from cactus and interpolates onto a different cactus
grid.  Uses AI Local Interp and not much internals of Cactus.  Is a
testsuite but no
good documentation.  Yosef is interested in this thorn and could review.

Steve B wants to come up with Obscure Cactus Knowledge question for the
meetings.  Educational and spreads the knowledge base, should encourage
humorous answers from us illiterati.

ticket 2413 https://bitbucket.org/einsteintoolkit/tickets/issues/2413 
Zach is
reviewer waveform extractor (or its post-summer versions) [RH]

** con2prim methods https://arxiv.org/abs/1712.07538 ticket 2414
https://bitbucket.org/einsteintoolkit/tickets/issues/2414 Maria is
reviewer [RH]

  Other groups are aiding these methods, like Federico Cipoletta to
GRHydro, and Wolfgang XX is also working on these methods.  Wolfgang's
method has
a proof of solution to roots...if it has a solution.  ZE, often with AMR
the conservatives can be ill-valued.  His code has a lot of
dependencies, Boost, Ninja, etc.

  ZE, the ideal interface for any GRMHD code is not a con2prim solver
that does everything at all points, but one where you call it and it
does it at one point. 
Convenient if you can do it in one OpenMP loop, so the point-by-point is
better.  Suppose it fails to find a root, if it fails fall-back to
another method.  Make the
interface a point-wise method.  RH agrees.  But point-wise is maybe the
other extreme, you may want that it takes a 1D array of data and then
flags individual
SIMD-parallelization a Newton-Raphson method.  ZE, in some cases it is
faster to us a quartic solver in some cases.

  RH, if this is a summer project for other groups with an end time,
suggest waiting until the end of summer to see what their results are.

ticket 2417 https://bitbucket.org/einsteintoolkit/tickets/issues/2417 
no reviewer

Steve says he might review this, and Peter D says he can help.

ZE, has made a couple of modifications.  And Antoni RB has shared their
Mathematica notebook with Zach and testing NRPyPN and has not found any
Techniques in the two efforts is different, particularly the radial
component to inject in two punctures.  Useful with permission, to copy
the method from the
Antoni et al. notebook.  ARB, will look at NRPyPN next week and compare
with our expression.  There is some freedom in some coefficients, but in
the end
Zach's method will work better in some parts of parameter space, and
will compare.

* gallery testing: tasks

** BNS: Shawn Rsofsky (UIUC).  In progress, needs to be uploaded, some
differences post-merger.

Shawn has done the simulation and plots but has not uploaded the data. 
RH re-ran it and does get the same waveforms, so the plots will not change.

**BBH: Peter Schaffarczyk (KEIL), Atul Kedia (Notre Dame) in progress

Peter S, took more time than expected.  Configure a new machine in
Berlin.  Is over with same time, and working on the graphics and
figures.  Gnuplot
graphics are finished.  Made afigure of the horizons and looks a little
different than the main page and discussing that.  Atul, Figures for
Curvature Scalars
is taking some time, and Ian Hinder is advising.  Focus mainly on the

* test.cactuscode.org issues

Nine critical issues at the above link.  SB advocates for not have the
Link to Live Wavetoy Example,
https://github.com/EinsteinToolkit/cactuscode.org/issues/17 . 
General agreement.  RH, fine to remove Live example, may on the other
hand take the 1D scalar wave equation into a Jupyter notebook and run on
the tutorial
server.  JPEG thorn should still work.  Have a cell that opens the Jpeg
file. SB says had trouble compiling it. 

SB, it would be nice to grow our collection of notebooks for tutorials
in general.

* Online ET Workshop https://www.cct.lsu.edu/Einsteintoolkitworkshop  [SB]

SB, not having an in-person event in August, very minimally we should
have a training for new users.  Live instructors.  Good to have some
talks too, work
being done with the toolkit, state of AMRex at that time.  Looking for
help and suggestions.  ZE, would student talks be good?  Have a student
working on
ETK.   SB, that would be great.  Like to see NRPy tutorials.  ZE, have a
collection of tutorials about constructing thorns.  SB, think about
things you would
like to present.  Putting together an agenda.  For online event maybe 3
hours a day is the limit.

* Next chair(s) and minute taker(s)

6-25 Chair Peter S.; Minute taker Roland
7-02 Chair Roland;  Minute taker Steve

* Other issues?

MH asks about con2prim.  RH, Univ. of Arizona talking with Zach about
Illinois GRMHD code modifications.  Will wait for results at end of summer.

MH your (SB) Christmas Tree?  SB, too lazy to take it down (and put back
up?)---so keep it unplugged until Christmas time.

ZE, Quick update, recent update bug fix to Baikal on very special
numbers of API process there was an interface with the boundary thorn
that caused
an exit and that is fixed.  Also other issue that with gcc 9+ Bailkal
takes a long time to compile.  So refactored the code and properly
doc-tested and
had one successful expt with scalar wave with calculation not done
inline but by function call and do not see a performance hit.  Hopefully
next week
can report that it is compiling fine/faster on gcc 9+ .

* unanswered questions on mailing list  

No unanswered email found.

* open tickets sorted by update time 

Tkt 2418
not entirely clear what you want the
macro to do, discuss offline.  RH, intended as a discussion item, could
add extra checks to Cactus.

* tickets ready for review 

--bill e.g.

William Gabella
Research Assistant Professor
Department of Physics and Astronomy
Vanderbilt University
Nashville, TN  USA

b.gabella at vanderbilt.edu
(o) 615-343-2713

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