The `Variant` class is templated to hold objects of other types.
Depending on whether those objects of are meant to be used in the
control or execution side, the methods on `Variant` might need to be
declared with (or without) special modifiers. We can sometimes try to
compile the `Variant` methods for both host and device and ask the
device compiler to ignore incompatibilities, but that does not always
work.
To get around that, create two different implementations of `Variant`.
Their API and implementation is exactly the same except one declares its
methods with `VTKM_CONT` and the other its methods `VTKM_EXEC`.
The ArrayPortalMultiplexer always called Set on the delegate portals.
However, sometimes the portals were not supported. Instead, only call
when the delegate is supported.
Probably the "right" thing to do would be to check all posible portals
for support, but that sounds like it would slow down the compile.
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.
A new header named TypeList.h and the type lists have been redefined in
this new file. All the types have been renamed from `TypeListTag*` to
`TypeList*`. TypeListTag.h has been gutted to provide deprecated
versions of the old type list names.
There were also some other type lists that were changed from using the
old `ListTagBase` to the new `List`.
The newer List operations should still work on the old ListTags, so make
those changes first to ensure that everything still works as expected if
given an old ListTag.
Next step is to deprecate ListTagBase itself and move all the lists to
the new types.
There was a warning comes from the functors in support of the portals
for ArrayHandleMultiplexer. The template has no good way to determine
whether the object it is calling is for control or execution, so it
supports both. It is not useful to warn when it happens to compile only
for the host.
This is done through a new version of ApplyPolicy. This version takes
a type of the array as its first template argument, which must be
specified.
This requires having a list of potential storage to try. It will use
that to construct an ArrayHandleMultiplexer containing all potential
types. This list of storages comes from the policy. A StorageList
item was added to the policy.
Types are automatically converted. So if you ask for a vtkm::Float64 and
field contains a vtkm::Float32, it will the array wrapped in an
ArrayHandleCast to give the expected type.
There was a special case for ArrayHandleMultiplexer where if you gave it
just one type it would treat that as a value type rather than an array
to support and instead provide a default list of types. However, GCC 4.8
is having trouble compiling the code to create the default list, the
semantics are confusing, and the more I think about it the less likely I
think we will need this functionality. So, just getting rid of that.
The code was working fine on all the dashboards except for the Visual
Studio 2015 compiles on delve. It gave an error like:
ArrayHandleMultiplexer.h(398): error C2938: 'ArrayHandleToStorageTag<unknown-type>' : Failed to specialize alias template
A StackOverflow article (https://stackoverflow.com/questions/43411542/
metaprogramming-failed-to-specialize-alias-template) suggests that this
is a bug in older versions of Visual Studio. Although fixed in more
recent versions, we might have to support older versions.
