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ianhinder / Kranc

A Mathematica package for generating code for solving time dependent partial differential equations
http://kranccode.org
GNU General Public License v2.0
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Use presync #148

Closed rhaas80 closed 4 years ago

rhaas80 commented 4 years ago

This pull requests adds support for Cactus' "PreSync" functionality to Kranc. Using PreSync the Driver, Boundary thorn and flesh collaborate to use the READS / WRITES statements in the schedule to keep track of which regions of the grid are valid and, if a READS requires data that is currently invalid but can be supplied by a SYNC and / or application of boundary and symmetry conditions, will execute those before a scheduled routine starts.

To this end a thorn has to inform the driver about the boundary condition to apply to each grid variable by calling a function of theDriver_SelectVarForBCI before the first SYNC. This patch introduces a convenience function Kranc_SelectVarForBCI which combines calls to Boundary_SelectVarForBCI and Driver_SelectVarForBCI, calling the latter only if it is aliased. Depending on the value of the Cactus parameter presync_mode the Driver / Boundary will ignore one of the calls Boundary_SelectVarFoBCI or Driver_SelectVarForBCI without any need by the user thorn to be aware of this parameter.

Coded the way it is in this pull request a Kranc generated thorn is usable for both a flesh / Driver that do support PreSync and ones that do not.

A second change involves Kranc's built in handling of access to the stress energy tensor. In CodeGenSchedule.m (diff without whitespace: https://github.com/ianhinder/Kranc/pull/148/files?diff=split&w=1) it generates READS clauses for the grid scalar indicating storage for Tmunu which is used in Kranc's auto-generated code to skip access to Tmunu when it has no storage (see https://github.com/ianhinder/Kranc/blob/8b36a2a7243dccb9f6867d34990dd07691a0d2d0/Tools/CodeGen/CodeGenCalculation.m#L573).

These two changes make up a minimal set of modifications to fully make use of the PreSync code in the flesh.

rhaas80 commented 4 years ago

Before applying the first couple of commits should be squashed so that in the end there are only 2 commits: 1 to introduce Kranc_SelectXForY and one to add a READS for stress_energy_state.

rhaas80 commented 4 years ago

I verified that a ET_2019_10_v0 version of McLachlan's MMA files can be translated using this version of Kranc, compiled and linked against ET_2019_10_v0 everything and passes all tests.

I will merge the branch into master (after squashing as indicated above) tomorrow May 27th.