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https://gitlab.kitware.com/vtk/vtk-m
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813f5a422f
The convenience functions `ArrayPortalToIteratorBegin()` and `ArrayPortalToIteratorEnd()` wouldn't detect specializations of `ArrayPortalToIterators<PortalType>` since the specializations aren't visible when the `Begin`/`End` functions are declared. Since the CUDA iterators rely on a specialization, the convenience functions would not compile on CUDA. Now, instead of specializing `ArrayPortalToIterators` to provide custom iterators for a particular portal, the portal may advertise custom iterators by defining `IteratorType`, `GetIteratorBegin()`, and `GetIteratorEnd()`. `ArrayPortalToIterators` will detect such portals and automatically switch to using the specialized portals. This eliminates the need for the specializations to be visible to the convenience functions and allows them to be usable on CUDA.
92 lines
3.4 KiB
C++
92 lines
3.4 KiB
C++
//============================================================================
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// Copyright (c) Kitware, Inc.
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// All rights reserved.
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// See LICENSE.txt for details.
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//
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// This software is distributed WITHOUT ANY WARRANTY; without even
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// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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// PURPOSE. See the above copyright notice for more information.
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//============================================================================
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#ifndef vtk_m_cont_ArrayPortal_h
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#define vtk_m_cont_ArrayPortal_h
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#include <vtkm/Types.h>
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namespace vtkm
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{
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namespace cont
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{
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#ifdef VTKM_DOXYGEN_ONLY
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/// \brief A class that points to and access and array of data.
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///
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/// The ArrayPortal class itself does not exist; this code is provided for
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/// documentation purposes only.
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///
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/// An ArrayPortal object acts like a pointer to a random-access container
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/// (that is, an array) and also lets you set and get values in that array. In
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/// many respects an ArrayPortal is similar in concept to that of iterators but
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/// with a much simpler interface and no internal concept of position.
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/// Otherwise, ArrayPortal objects may be passed and copied around so that
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/// multiple entities may be accessing the same array.
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///
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/// An ArrayPortal differs from an ArrayHandle in that the ArrayPortal is a
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/// much lighterweight object and that it does not manage things like
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/// allocation and control/execution sharing. An ArrayPortal also differs from
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/// a Storage in that it does not actually contain the data but rather
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/// points to it. In this way the ArrayPortal can be copied and passed and
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/// still point to the same data.
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///
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/// Most VTKm users generally do not need to do much or anything with
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/// ArrayPortal objects. It is mostly an internal mechanism. However, an
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/// ArrayPortal can be used to pass constant input data to an ArrayHandle.
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///
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/// Although portals are defined in the execution environment, they are also
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/// used in the control environment for accessing data on the host.
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///
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/// Since utilities like IsWritableArrayHandle checks for the existence of a Set
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/// method on a portal, if the portal is backed by a read-only ArrayHandle, the
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/// Set method must not be defined. If the portal may or may not be writable
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/// (e.g., ArrayHandleCast may be casting a read-only OR read-write array), the
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/// Set method may be conditionally removed using SFINAE.
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///
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/// The ArrayPortalToIterators utilities wrap ArrayPortals in STL-style
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/// iterators. If an ArrayPortal implementation wishes to provide a custom
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/// iterator type, it may define an IteratorType type alias along with the
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/// methods `IteratorType GetIteratorBegin()` and
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/// `IteratorType GetIteratorEnd()`. These are not required members, but if
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/// present, will allow additional optimizations for certain portals.
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///
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template <typename T>
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class ArrayPortal
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{
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public:
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/// The type of each value in the array.
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///
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using ValueType = T;
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/// The total number of values in the array. They are index from 0 to
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/// GetNumberOfValues()-1.
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///
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VTKM_EXEC_CONT
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vtkm::Id GetNumberOfValues() const;
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/// Gets a value from the array.
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///
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VTKM_EXEC_CONT
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ValueType Get(vtkm::Id index) const;
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/// Sets a value in the array. If it is not possible to set a value in the
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/// array, this method must not be defined.
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///
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VTKM_EXEC_CONT
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void Set(vtkm::Id index, const ValueType& value) const;
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};
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#endif // VTKM_DOXYGEN_ONLY
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}
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} // namespace vtkm::cont
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#endif //vtk_m_cont_ArrayPortal_h
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