EPW v6.1 — does -ni > 1 now work with ephwrite, and has it been built with Intel oneAPI?

[RMaghetti]

Two questions prompted by the v6.1 release announcement, which is locked, so I'm posting here. Both concern the extended two-level parallelization, from a user who just hit its limit in v6.0.

1. Does -ni > 1 now work with ephwrite = .true.?

On v6.0 it does not. A job launched as

mpiexec -n 100 --ppn 100 epw.x -nk 10 -ni 10 -in epw.in

terminated at 0.07 s with EPW reporting that ephwrite = .true. is incompatible with image parallelization. Since EPW has no plane-wave parallelization, ranks must equal pools, and pools are bounded by the coarse k-point count — 64 in my case. That capped my anisotropic Eliashberg calculation at a single node with no way to extend it.

The release note says two-level parallelization "has been extended across EPW" and "supports parallelization of calculations involving both coarse and fine electron and phonon grids." Does that include the ephwrite path, or does the restriction remain?

2. Has v6.1 been built with the Intel oneAPI toolchain?

The GPU offloading note lists CUDA, OpenACC and OpenMP target offloading. I am on Aurora at ALCF (Intel Ponte Vecchio, oneAPI), currently running the QE 7.5 / EPW v6.0 CPU build. Kim, Liu, Tiwari, Margine and Giustino (arXiv:2603.10295) report v6.1 scaling on Aurora, so I assume the toolchain works — but I have not found installation guidance specific to oneAPI, and I would rather ask than guess before requesting a build from facility staff.

For context: I have just completed an independent reproduction of an anisotropic Migdal-Eliashberg study using v6.0 on Aurora (SrB3C3, Wang, Yan & Gao, PRB 103, 144515). Ten quantities agree with the published values, including the gap anisotropy ratio at 5 K to 0.05%. The whole campaign took 22 node-hours on single nodes. If measured Aurora timings or configuration details would be useful to the developers, I am glad to provide them.

Thank you, Rick Maghetti Resonance Materials LLC ALCF Director's Discretionary allocation 16463 (Aurora)

[stiwari]

Dear Rick,

1. Unfortunately, ephwrite is still not image parallelized. Apart from that, most of epw now supports two-level parallelization including coarse-grid q-parallelization over irreducible q-points.

2. Yes, EPW has been both built and benchmarked with intel oneAPI toolchain on Aurora.

Let us know if you have more questions regarding EPW v6.1.

Best regards,
Sabya.