Fiddling around with some parameters for the litmus test driver:
- It seems that having only a subset of the running blocks participate
  in the Message Passing litmus test increases the rate at which weak
  memory behaviors are observed.
- Pre-stressing memory doesn't seem to help on NVIDIA V100s.

Store buffering is an observable behavior where a store may be reordered
after a load. This exercises MemoryOrderSeqCst.

- Use a forall device kernel to check results
- Interleave order of operations between testing threads
- Only warn on a lack of observed relaxed behaviors

Correctly use the stress testing formulation from the paper, "Foundations
of Empirical Memory Consistency Testing" (OOPSLA 2020). Instead of having
all stressing blocks scatter their accesses across the "stressing" array,
select a small-ish subset of 64-word lines and stripe them across the
stressing blocks. This increases the stress on the contention hardware
in a GPU.

Synchronize testing blocks and stressing blocks together on each
iteration.