Integrate Modified AC-SpGEMM / GALATIC

[richardlett]

GALATIC repo isn't public yet, draft PR. Don't accept

Notes:

• C++14 now required
• CUDA 11 now required
• --expt-relaxed-constexpr now required. We can remove this with a hack, if need be.
  • (we depend on std::limit , I think, to find max of an integral type parameter - technically not legal CUDA, but it's a constexpr, so it's evaluated at compile time anyway)

512 thread AC-SpGEMM/GALATIC version differs in most parameters due to large shared memory because # of threads, otherwise stuck with defaults. May have issues with merging -- needs testing.

• I haven't looked at larger matrices (mostly curious about merging with 512 threads) or did perf testing
• currently only threads configurable parameter
• more optimized for smaller sized types, don't have contingency for larger sized types. Not sure if I'm the bottle neck ATM

[richardlett]

Sorry for delay, that should do it!

[cyborgshead]

@ctcyang @richardlett made Galactic public and I think that it will be a huge movement for gunrock's graphblas to support not only default matrix format but sparse with csr that will open the road to huge graph processing

Will be great if examples will be also updated I hope that that development will be continued because there is increasing interest in graph processing, especially with graphblas, and gunrock may push this movement with leading GPU support