*Meeting Minutes – February 6, 2025* Present: Erik, Lucas, Roland, Liwei, Zach, Steve, Swapnil, Jay, Helvi, Allen ------------------------------ Liwei:

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Comparing performance between Carpet and CarpetX. -

Findings: -

One refinement level test shows similar speeds. -

With six levels, CarpetX is about 20% slower (with and without subcycling). -

Removing additional synchronization calls for interprocess boundaries (ghost-zones) and keeping sync calls only for prolongation during the substep makes the speed comparable to Carpet. -

Further optimizations are in progress. -

Erik’s suggestion: Introduce a new grid point type to track prolongation boundaries and set a flag to check if they are synced. -

Another potential issue: Using the PointDesc object (p.I) in CarpetX causes minor slowdowns compared to accessing indices in Carpet. -

Erik’s input: The compiler should optimize this; Liwei will share an example .o file for Erik to analyze.

Roland:

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Z4c requires a test case. -

Currently working on it and may seek Steve’s review later.

Lucas:

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Testing hybrid Runge-Kutta integrators with BBH simulations. -

Successfully set up a multipatch system with two puncture data and extracted multipole data. -

May need assistance with Z4c. -

Updating the robust stability test parfile and will open a PR. Currently experimenting with different boundary conditions. -

Reviewing PRs for NewRadX in SpacetimeX and CarpetX repositories. -

Zach’s question: Any tests beyond scalar wave for multipatch? -

Lucas is working on a BBH test case and aims for completion before the May release. -

Helvi’s question: Status of multipatch implementation in CanudaX? -

Lucas is still working on it. -

Liwei’s question: Can the multipatch code be used directly? -

Lucas explained that evolution codes must be modified to compute derivatives and project them onto the multipatch system. -

Suggests adding an option to enable/disable multipatch rather than maintaining two code versions.

------------------------------ Next Meeting:

Thursday, February 13, 2025 @ 10 AM CDT / 11 AM EST