This fixes an issue where getting a `ReadPortal` or a `WritePortal` from
an `ArrayHandleVirtual` could cause a deadlock from a held token even if
the returned portal was detached or destroyed.
The problem was that `ArrayHandleVirtual` was keeping a reference to the
`ArrayPortal` from the concrete array. This was because the returned
`ArrayPortalRef`, which was designed to work on both control and
execution environments, had no good way to destroy the portal. This
meant that the `ArrayHandleVirtual` was caching a copy of the concrete
array's portal. This was not a great idea before because the array could
get invalidated. It is worse now because it keeps the concrete array
locked.
Fixed the problem by subclassing `vtkm::ArrayPortalRef` to make a
control-specific version that will delete the concrete portal on its own
destruction.
Fixes#277
DeviceAdapterError existed to make sure that the default device adapter
template was being handled properly. Since the default device adapter doesn't
exist, and nothing is templated over it we can now remove DeviceAdapterError.
Previously, ArrayHandleVirtual was using the default Transfer object.
This was problematic because it would copy/allocate things in the
execution environment independently from the array that it was wrapped
around. This caused several negative effects, particularly for CUDA
devices. First, if the data were already on the device (or the array is
implicit), a second copy of the data would be made. Second, the copy to
the device is likely less efficient. Third (and worst of all), the data
did not always get pulled back to the original array correctly.
This commit also contains instantiations of ArrayHandleVirtual and its
components for the most common types.
Previously, ArrayHandleVirtual was defined as a specialization of
ArrayHandle with the virtual storage tag. This was because the storage
object was polymorphic and needed to be handled special. These changes
moved the existing storage definition to an internal class, and then
managed the pointer to that implementation class in a Storage object
that can be managed like any other storage object.
Also moved the implementation of StorageAny into the implementation of
the internal storage object.
