Getting the number of components (or the number of flattened components)
from an `ArrayHandle` is usually trivial. However, if the `ArrayHandle` is
special in that the number of components is specified at runtime, then it
becomes much more difficult to determine.
Getting the number of components is most important when extracting
component arrays (or reconstructions using component arrays) with
`UnknownArrayHandle`. Previously, `UnknownArrayHandle` used a hack to get
the number of components, which mostly worked but broke down when wrapping
a runtime array inside another array such as `ArrayHandleView`.
To prevent this issue, the ability to get the number of components has been
added to `ArrayHandle` proper. All `Storage` objects for `ArrayHandle`s now
need a method named `GetNumberOfComponentsFlat`. The implementation of this
method is usually trivial. The `ArrayHandle` template now also provides a
`GetNumberOfComponentsFlat` method that gets this information from the
`Storage`. This provides an easy access point for the `UnknownArrayHandle`
to pull this information.
StorageType is public in vtkm::cont::ArrayHandle, but some subclasses
re-declare it as private. Having it public provides a convenient way to
get the storage type of an ArrayHandle, otherwise it is quite verbose.
Addresses: #314
The `VecTraits` class allows templated functions, methods, and classes to
treat type arguments uniformly as `Vec` types or to otherwise differentiate
between scalar and vector types. This only works for types that `VecTraits`
is defined for.
The `VecTraits` templated class now has a default implementation that will
be used for any type that does not have a `VecTraits` specialization. This
removes many surprise compiler errors when using a template that, unknown
to you, has `VecTraits` in its implementation.
One potential issue is that if `VecTraits` gets defined for a new type, the
behavior of `VecTraits` could change for that type in backward-incompatible
ways. If `VecTraits` is used in a purely generic way, this should not be an
issue. However, if assumptions were made about the components and length,
this could cause problems.
Fixes#589
The `GetNumberOfComponents` and `GetNumberOfComponentsFlat` methods in
`UnknownArrayHandle` have been updated to correctly report the number of
components in special `ArrayHandle`s where the `Vec` sizes of the values
are not selected until runtime.
Previously, these methods always reported 0 because the value type could
not report the size of the `Vec`. The lookup has been modified to query the
`ArrayHandle`'s `Storage` for the number of components where supported.
Note that this only works on `Storage` that provides a method to get the
runtime `Vec` size. If that is not provided, as will be the case if the
number of components can vary from one value to the next, it will still
report 0.
This feature is implemented by looking for a method named
`GetNumberOfComponents` is the `Storage` class for the `ArrayHandle`. If
this method is found, it is used to query the size at runtime.
When you use an `ArrayHandle` as an output array in a worklet (for example,
as a `FieldOut`), the fetch operation does not read values from the array
during the `Load`. Instead, it just constructs a new object. This makes
sense as an output array is expected to have garbage in it anyway.
This is a problem for some special arrays that contain `Vec`-like objects
that are sized dynamically. For example, if you use an
`ArrayHandleGroupVecVariable`, each entry is a dynamically sized `Vec`. The
array is referenced by creating a special version of `Vec` that holds a
reference to the array portal and an index. Components are retrieved and
set by accessing the memory in the array portal. This allows us to have a
dynamically sized `Vec` in the execution environment without having to
allocate within the worklet.
The problem comes when we want to use one of these arrays with `Vec`-like
objects for an output. The typical fetch fails because you cannot construct
one of these `Vec`-like objects without an array portal to bind it to. In
these cases, we need the fetch to create the `Vec`-like object by reading
it from the array. Even though the data will be garbage, you get the
necessary buffer into the array (and nothing more).
Previously, the problem was fixed by creating partial specializations of
the `Fetch` for these `ArrayHandle`s. This worked OK as long as you were
using the array directly. However, the approach failed if the `ArrayHandle`
was wrapped in another `ArrayHandle` (for example, if an `ArrayHandleView`
was applied to an `ArrayHandleGroupVecVariable`).
To get around this problem and simplify things, the basic `Fetch` for
direct output arrays is changed to handle all cases where the values in the
`ArrayHandle` cannot be directly constructed. A compile-time check of the
array's value type is checked with `std::is_default_constructible`. If it
can be constructed, then the array is not accessed. If it cannot be
constructed, then it grabs a value out of the array.
This feature enables the ability to anonomously create an array (such as
with `UnknownArrayHandle::NewInstance()`) and then use that as an output
array.
Previously, the number of buffers held by an `ArrayHandle` had to be
determined statically at compile time by the storage. Most of the time
this is fine. However, there are some exceptions where the number of
buffers need to be selected at runtime. For example, the
`ArrayHandleRecombineVec` does not specify the number of components it
uses, and it needed a hack where it stored buffers in the metadata of
another buffer, which is bad.
This change allows the number of buffers to vary at runtime (at least at
construction). The buffers were already managed in a `std::vector`. It
now no longer forces the vector to be a specific size.
`GetNumberOfBuffers` was removed from the `Storage`. Instead, if the
number of buffers was not specified at construction, an allocation of
size 0 is done to create default buffers.
The biggest change is to the interface of the storage object methods,
which now take `std::vector` instead of pointers to `Buffer` objects.
This adds a little hastle in having to copy subsets of this `vector`
when a storage object has multiple sub-arrays. But it does simplify some
of the templating.
Using this internal class is a bit tricky because it requires a pointer
to a C array that is expected to contain portals. Both the C array and
the portals must be defined for the expected device. This is already
handled by the associated Storage. Assuming all of this holds, make sure
the `ArrayPortalRecombineVec` is trivially copyable. This is a
requirement for passing objects to the execution environment.
Unfortunately, there is no way to specify when copying `RecombineVec`s
whether we wish to allow precision loss in conversions. Because
sometimes we need them, disable the warnings.
3228752b2 Fix error message when using deprecated storage
5ef4e7eee Make new style of ArrayHandle the expected style
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Robert Maynard <robert.maynard@kitware.com>
Merge-request: !2375
`RecombineVec` is the class used as the value type for
`ArrayHandleRecombineVec`. It is a `Vec`-like object, but has several
limitations (including arithmetic operators like `+` won't work).
Arithmetic assignment operators are useful so you don't have to create
impossible intermediate values.
What was previously declared as `ArrayHandleNewStyle` is now just the
implementation of `ArrayHandle`. The old implementation of `ArrayHandle`
has been moved to `ArrayHandleDeprecated`, and `ArrayHandle`s still
using this implementation must declare `VTKM_ARRAY_HANDLE_DEPRECATED` to
use it.
Some of the special `ArrayHandle`s require specialized versions of
`vtkm::exec::arg::Fetch`. The specializations were not put in the
respective vtkm/exec/arg/Fetch*.h header files because the definition of
the `ArrayHandle`s was not available there. The implementation was in
the ArrayHandle*.h files, but it is hard to find the specialization
there.
Instead, make a secondary header file in vtkm/exec/arg that implements
the Fetch specialization and include it from the ArrayHandle*.h file.
That way, the basic Fetch does not have to include odd `ArrayHandle`
types but the `Fetch` implemenations are still all located together.
`ArrayHandleRecombineVec` is used when calling
`ExtractArrayFromComponents` from `UnkownArrayHandle`. It needs special
handling with the `Fetch` for an output array.
The primary purpose of `ArrayHandleRecombineVec` is to take arrays
returned from `ArrayExtractComponent` and recombine them again into a
single `ArrayHandle` that has `Vec` values.
