[gmx-developers] GMX_BARRIER in gmx_pme_do()

[Zhang Cheng]

Hi, 

I am wondering whether the GMX_BARRIER(cr->mpi_comm_mysim) calls in pme.c/gmx_pme_do() should be replaced by GMX_BARRIER(cr->mpi_comm_mygroup), especially when there are PME only nodes. I understand (but I may be wrong) gmx_pme_do() is only called by a PP+PME or PME-only processor, so mpi_comm_mygroup should be sufficient in either case. On the other hand, mpi_comm_mysim will hang a PP only processor if PP and PME are done on separate nodes.  I also understand GMX_BARRIER is not invoked unless BARRIERS is defined, but it still appears to be a little confusing to me.

Thanks,
Cheng