#2101: Add Lean_public and Proca thorns to the ET ---------------------------------------+--------------------------------- Reporter: miguel.zilhao.nogueira@… | Owner: Steven R. Brandt Type: enhancement | Status: assigned Priority: major | Milestone: ET_2018_08 Component: EinsteinToolkit thorn | Version: development version Resolution: | Keywords: Lean_public ---------------------------------------+---------------------------------
Comment (by Peter Diener):
Here is my review of the "Proca" suite of thorns that are proposed for inclusion in the Einstein Toolkit. Proca consists of ProcaBase, Proca_simpleID, TwoPunctures_KerrProca and ProcaEvolve and NPScalars_Proca. The code is nicely written, but mainly lack some tests and documentation.
Questions, comments and recommendations regarding Proca overall:
There are two tests in ProcaEvolve of which one uses Lean and the other ML_BSSN while otherwise appear to be the same. Whereas the Ai and Ei variables agree quite well, there seems to be significant differences between Aphi and Zeta. Is this expected? If so, why?
In ProcaEvolve there is another parameter file in the test directory (ML_BSSN_Aphi_mu0.4_c100.1_r06_S0.0_4th.par) that does not have any associated output. If this was meant to be a test, output should be provided. Otherwise it should be moved to the example parameter file directory.
NPScalars_Proca, Proca_simpleID and TwoPunctures_KerrProca have no tests of their own. Proca_simpleID is tested by the tests in ProcaEvolve, but NPScalars_Proca and TwoPunctures_KerrProca should definitely be covered by tests. You may also consider making a standalone test for Proca_simpleID.
None of the thorns in the Proca arrangement have any documentation of their own. As there is a paper describing the formulation, it is okay to refer to the paper, but there should be some description of the variables and parameters used in the code and how they relate to the physics and equations.
It would be nice if all he parameter files for the runs in the paper could be made available as examples of how to use the thorn. Currently there are only two example parameter files available and it's not immediately clear if they have been used for the paper. There could be a comment at the top of the parameterfiles indicating what section and/or figure in the paper they were used for.
Questions, comments and recommendations specifically to ProcaBase:
In parameter.ccl the comment to the value of the parameter mu says: "any non-negative number". However, the range allows for zero and in fact the default value is zero. Either the comment should be changed or the range and default value should be changed.
Are the integer power for the fall off rate for the outgoing boundary conditions for the Proca variables not known? Or can they be different for different physical systems? If they are known constants, should they be parameters at all? Also could the power be different for different components of the E and A vectors. If not, there's no need to make these vector parameters.
I propose to give the file (src/Basegrid.F90) with the symmetry registering routine a more descriptive name.
It would be nice to have a proper (but short) thorn documentation to relate the variables with the paper.
Questions, comments and recommendations specifically to Proca_simpleID:
The Simple Initial Data solution in the paper is a spherical symmetric solution. The parameters for Proca_simpleID on the other hand seem to allow for a superposition of 2 such solutions separated by a non-zero distance. As the parameter for the separation can not be zero (imposed by the parameter range) the initial data thorn will thus never produce initial data that is spherically symmetric around the origin of the cactus grid. Would it make sense for the range of par_b to include zero in order to allow for that. This is something worth explaining in the (missing) documentation.
Questions, comments and recommendations specifically to TwoPunctures_KerrProca:
It looks like the code implements initial data with a Y_11 angular dependence in addition to Y_00 and Y_10 mentioned in the paper. This should be in the documentation.
There's a comment in Equations.c that some of the equations were copied from Mathematica. Could that mathematica notebook be made available in the thorn as well?
In the future it might be worth considering some way of merging this back into the original TwoPunctures, so we don't have multiple thorns implementing the same spectral solver infrastructure.
There should be tests for all the different types of angular profiles for the initial data.
The discussion in the README should be converted into a proper thorn documentation.
Questions, comments and recommendations specifically to ProcaEvolve:
Need a thorn documentation to relate variables to the paper and to explain the use of parameters.
I don't know how much performance is a concern. If only a tiny amount of time is spent in Proca compared to BSSN (or other things) this is obviously not important. However, if the issues with the code, that prevents the compiler from optimizations, makes the code slow enough that the time spent in Proca is comparable to the time spent in BSSN it might be worth it to fundamentally rewrite the code. One of the problems, is the many nested loops over tensor indices. These prevents the compiler from vectorizing most of the RHS code (I checked this by looking at compiler vectorization output from the Intel compiler). As the loop lengths are just 3, the vectorizer deems that vectorization will be ineffecient and hence doesn't do it. On modern CPUs with vector lengths of 4 or 8 (in double precision), efficiently using the vector units is really important for good performance. However, this is not an issue (if there really is a problem with performance) that should prevent inclusion in the ET, but just something to think about for later.