UCL Scotch support for SWIFT

[MatthieuSchaller]

@pwdraper, for the records, could we list here the issues we had not resolved? I think the main one was the lack of 64-bits support and the inability for scotch to evolve a previous partition?

[themkots]

@MatthieuSchaller , @pwdraper , @DanGiles There are the things that @MatthieuSchaller mentions just above (32-bit linking where we expected 64-bit one, no refinement -- for the scotch-version, not the ptscotch one -- we had no time investigating ptsccotch, as per this issue messages, and I find hard to believe that ptscotch does not do an incremental refinement -- otherwise how can it do parallelisation/mpi stuff ?? --) There is also the hard-wired graph-connectivity issue that metis/parmetis seem not to cross over, but scotch does, i.e. when it finds more that <hard wired number? cannot remember right now - is in src - 64? something else?> nodes able to communicate with one another, it tries to leverage this large connectivity for load/compute/comms balance, but this results in runtime error from code when discovering so in graph partitioning call.

Wish we had more time to delve into those issues, and a) have 64-bit clean builds, b) explore the obvious strategy of incremental refinement, c) explore large connectivity for better / lower than say 5% gaps.

Ta.

[MatthieuSchaller]

Thanks Themys!

For the 64-bits build, do you recall whether it's a problem of creating a clean build or what is a more fundamental lack of support? My memory says it's the latter.

[themkots]

Yes, it is their source that links the 32 bit one --- could attempt a direct edit, or send a PR, if in github somehow, but not right now...