Previously vtk-m allowed users to issue atomic loads on constant
values which is problematic for the following reasons:
- can be a source of undefined behavior
- not supported by kokkos
This issue was detected when using kokkos HIP atomic implementation
Now that we have the functions in `vtkm/Atomic.h`, we can deprecate (and
eventually remove) the more cumbersome classes `AtomicInterfaceControl`
and `AtomicInterfaceExecution`.
Also reversed the order of the `expected` and `desired` parameters of
`vtkm::AtomicCompareAndSwap`. I think the former order makes more sense
and matches more other implementations (such as `std::atomic` and the
GCC `__atomic` built ins). However, there are still some non-deprecated
classes with similar methods that cannot easily be switched. Thus, it's
better to be inconsistent with most other libraries and consistent with
ourself than to be inconsitent with ourself.
The old version of ExecutionObject (that only takes a device) is still
supported, but you will get a deprecated warning if that is what is
defined.
Supporing this also included sending vtkm::cont::Token through the
vtkm::cont::arg::Transport mechanism, which was a change that propogated
through a lot of code.
The collection of connectivity algorithms had a couple of inefficiencies.
By moving to using WorkId we can remove a couple of arrays of the same size
as the input domain. In addition by moving to using atomics we can remove
an bool output array with a size equivalent to the input domain and
a call to reduce.
- Use AtomicInterface to implement device-specific atomic operations.
- Remove DeviceAdapterAtomicArrayImplementations.
- Extend supported atomic types to include unsigned 32/64-bit ints.
- Add a static_assert to check that AtomicArray type is supported.
- Add documentation for AtomicArrayExecutionObject, including a CAS
example.
- Add a `T Get(idx)` method to AtomicArrayExecutionObject that does
an atomic load, and update existing CAS usage to use this instead
of `Add(idx, 0)`.
