Add SubView class

include/RAJA/RAJA.hpp

@@ -118,7 +118,7 @@
 #include "RAJA/util/StaticLayout.hpp"
 #include "RAJA/util/IndexLayout.hpp"
 #include "RAJA/util/View.hpp"
-
+#include "RAJA/util/SubView.hpp"
 
 //
 // View for sequences of objects

include/RAJA/util/SubView.hpp

@@ -0,0 +1,268 @@
+/*!
+ ******************************************************************************
+ *
+ * \file
+ *
+ * \brief   RAJA header file defining the SubView class
+ *
+ ******************************************************************************
+ */
+
+//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~//
+// Copyright (c) 2016-25, Lawrence Livermore National Security, LLC
+// and RAJA project contributors. See the RAJA/LICENSE file for details.
+//
+// SPDX-License-Identifier: (BSD-3-Clause)
+//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~//
+
+#ifndef RAJA_SUBVIEW_HPP
+#define RAJA_SUBVIEW_HPP
+
+#include "RAJA/util/for_each.hpp"
+#include "RAJA/util/macros.hpp"
+#include "RAJA/util/types.hpp"
+#include "camp/tuple.hpp"
+#include "camp/array.hpp"
+
+namespace RAJA
+{
+
+template<typename IndexType = Index_type>
+struct RangeSlice {
+    IndexType start_, end_; 
+
+    static constexpr bool reduces_dimension = false;
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType map_index(const IndexType& idx) const {
+        return start_ + idx;
+    }
+
+    template<IndexType DIM, typename LayoutType>
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType size(const LayoutType&) const {
+        return (end_ - start_ + 1);
+    }
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType stride() const {
+        return 1;
+    }
+};
+
+template<typename IndexType = Index_type>
+struct RangeStartSlice {
+    IndexType start_; 
+
+    static constexpr bool reduces_dimension = false;
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType map_index(const IndexType& idx) const {
+        return start_ + idx;
+    }
+
+    template<IndexType DIM, typename LayoutType>
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType size(const LayoutType& layout) const {
+        return (layout.size() - start_);
+    }
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType stride() const {
+        return 1;
+    }
+};
+
+template<typename IndexType = Index_type>
+struct FixedSlice { 
+    IndexType idx_; 
+
+    static constexpr bool reduces_dimension = true;
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType map_index(const IndexType&) const {
+        return idx_;
+    }
+
+    template<IndexType DIM, typename LayoutType>
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType size(const LayoutType&) const {
+        return 1;
+    }
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType stride() const {
+        return 1;
+    }
+
+};
+
+template<typename IndexType = Index_type>
+struct NoSlice { 
+    static constexpr bool reduces_dimension = false;
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType map_index(const IndexType& idx) const {
+        return idx;
+    }
+
+    template<IndexType DIM, typename LayoutType>
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType size(const LayoutType& layout) const {
+        return layout.template get_dim_size<DIM>();
+    }
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType stride() const {
+        return 1;
+    }
+};
+
+template<typename IndexType = Index_type>
+struct StridedSlice { 
+    IndexType start_, end_, stride_;
+
+    static constexpr bool reduces_dimension = false;
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType map_index(const IndexType& idx) const {
+        return start_ + stride_ * idx;
+    }
+
+    template<IndexType DIM, typename LayoutType>
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType size(const LayoutType&) const {
+        return (end_ - start_) / stride_ + 1;
+    }
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr IndexType stride() const {
+        return stride_;
+    }
+};
+
+template<typename IndexType, typename... Slices>
+RAJA_INLINE RAJA_HOST_DEVICE constexpr auto make_slice_to_parent_index_map() {
+    IndexType sub_idx = 0;
+    IndexType i = 0;
+    camp::array<IndexType, sizeof...(Slices)> map = {};
+    ((map[i++] = (Slices::reduces_dimension ? -1 : sub_idx++)), ...);
+    return map;
+}
+
+template<typename IndexType, size_t n_parent_dims, typename... Slices>
+RAJA_INLINE RAJA_HOST_DEVICE constexpr auto make_parent_to_slice_index_map() {
+    IndexType sub_idx = 0;
+    IndexType i = 0;
+    camp::array<IndexType, n_parent_dims> map = {};
+
+    auto process_slice = [&](auto slice_type) constexpr {
+        if constexpr (!decltype(slice_type)::reduces_dimension) {
+            map[sub_idx++] = i++;
+        } else {
+            i++;
+        }
+    };
+
+    (process_slice(Slices{}), ...);
+
+    return map;
+}
+
+template <typename LayoutType, typename SliceTypes, typename IndexType = Index_type>
+struct SubRegion;
+
+/* SubLayout is a semantic alias for a SubRegion whose parent is a layout */
+template <typename LayoutType, typename SliceTypes, typename IndexType = Index_type>
+using SubLayout = SubRegion<LayoutType, SliceTypes, IndexType>;
+
+/* SubView is a semantic alias for a SubRegion whose parent is a view */
+template <typename LayoutType, typename SliceTypes, typename IndexType = Index_type>
+using SubView = SubRegion<LayoutType, SliceTypes, IndexType>;
+
+template <typename LayoutType, typename IndexType, typename... Slices>
+struct SubRegion<LayoutType, camp::list<Slices...>, IndexType> {
+
+    using IndexLinear = IndexType;
+
+    const LayoutType& parent_;
+    camp::tuple<Slices...> slices_;
+
+    static inline constexpr size_t num_slices_ = sizeof...(Slices);
+
+    static inline constexpr 
+    IndexType n_dims = ((Slices::reduces_dimension == false ? 1 : 0) + ...);
+
+    static inline constexpr 
+    camp::array<IndexType, num_slices_> slice_to_parent_map_ = 
+        make_slice_to_parent_index_map<IndexType, Slices...>();
+
+    static inline constexpr 
+    camp::array<IndexType, n_dims> parent_to_slice_map_ = 
+        make_parent_to_slice_index_map<IndexType, n_dims, Slices...>();
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr SubRegion(const LayoutType& parent, Slices... slices)
+        : parent_(parent), slices_(slices...) { }
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr auto& get_parent() const {
+        return parent_;
+    }
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr auto& get_slices() const {
+        return slices_;
+    }
+
+    template<IndexType Index>
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr auto& get_slice() const {
+        return camp::get<Index>(slices_);
+    }
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr auto size() const {
+
+        IndexType prod_dims = 1;
+        for_each_tuple_index( slices_,
+            [&](auto slice, auto index) {
+                const IndexType dim_size = slice.template size<index>(parent_);
+                prod_dims *= (dim_size == 0) ? 1 : dim_size;
+            });
+
+        return prod_dims;
+    }
+
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr auto size_noproj() const {
+
+        IndexType prod_dims = 1;
+        for_each_tuple_index( slices_,
+            [&](auto slice, auto index) {
+                prod_dims *= slice.template size<index>(parent_);
+            });
+
+        return prod_dims;
+    }
+
+    template<IndexType DIM> 
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr auto get_dim_size() const {
+        constexpr auto SliceDim = parent_to_slice_map_[DIM];
+        return camp::get<SliceDim>(slices_).template size<DIM>(parent_);
+    }
+
+    template<IndexType DIM> 
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr auto get_dim_stride() const {
+        constexpr auto SliceDim = parent_to_slice_map_[DIM];
+        return camp::get<SliceDim>(slices_).stride();
+    }
+
+    template <typename... Idxs>
+    RAJA_INLINE RAJA_HOST_DEVICE constexpr auto operator()(Idxs... idxs) const {
+        static_assert(sizeof...(idxs) == n_dims, "Wrong number of indices");
+
+        camp::array<IndexType, n_dims> arr{idxs...};
+        camp::array<IndexType, num_slices_> parent_indices;
+
+        for_each_tuple_index( slices_,
+            [&](auto slice, auto index) {
+                if (slice_to_parent_map_[index] >= 0) {
+                    parent_indices[index] = slice.map_index(arr[slice_to_parent_map_[index]]); 
+                } else {
+                    // map_index will not need index values for dimension-reducing slices
+                    // so we pass a "dummy" value.
+                    constexpr IndexType dummy_value = -1;
+                    parent_indices[index] = slice.map_index(dummy_value); 
+                }
+            });
+
+        return camp::apply(parent_, parent_indices);
+    }
+};
+
+template <typename LayoutType, typename... Slices>
+SubRegion(LayoutType, Slices...) -> SubRegion<LayoutType, camp::list<Slices...>>;
+
+}  // namespace RAJA
+
+#endif

include/RAJA/util/TypedViewBase.hpp

@@ -669,16 +669,31 @@ class ViewBase
   constexpr layout_type const& get_layout() const { return m_layout; }
 
   RAJA_HOST_DEVICE
-
   RAJA_INLINE
   constexpr linear_index_type size() const { return m_layout.size(); }
 
+  RAJA_HOST_DEVICE
+  RAJA_INLINE
+  constexpr linear_index_type size_noproj() const { return m_layout.size_noproj(); }
+
+  template<camp::idx_t DIM>
+  RAJA_INLINE RAJA_HOST_DEVICE constexpr linear_index_type get_dim_stride() const
+  {
+    return m_layout.template get_dim_stride<DIM>();
+  }
+
   template<camp::idx_t DIM>
   RAJA_HOST_DEVICE RAJA_INLINE constexpr linear_index_type get_dim_size() const
   {
     return m_layout.template get_dim_size<DIM>();
   }
 
+  template<camp::idx_t DIM>
+  RAJA_INLINE RAJA_HOST_DEVICE constexpr linear_index_type get_dim_begin() const
+  {
+    return m_layout.template get_dim_begin<DIM>();
+  }
+
   template<typename... Args>
   RAJA_HOST_DEVICE RAJA_INLINE constexpr view_return_type_t<value_type,
                                                             pointer_type,

include/RAJA/util/View.hpp

@@ -154,6 +154,7 @@ struct MultiView
   using value_type      = ValueType;
   using pointer_type    = PointerType;
   using layout_type     = LayoutType;
+  using linear_index_type = typename layout_type::IndexLinear;
   using nc_value_type   = camp::decay<value_type>;
   using nc_pointer_type = NonConstPointerType;
   using NonConstView =
@@ -228,6 +229,32 @@ struct MultiView
     return layout;
   }
 
+  RAJA_HOST_DEVICE
+  RAJA_INLINE
+  constexpr linear_index_type size() const { return layout.size(); }
+
+  RAJA_HOST_DEVICE
+  RAJA_INLINE
+  constexpr linear_index_type size_noproj() const { return layout.size_noproj(); }
+
+  template<camp::idx_t DIM>
+  RAJA_INLINE RAJA_HOST_DEVICE constexpr linear_index_type get_dim_stride() const
+  {
+    return layout.template get_dim_stride<DIM>();
+  }
+
+  template<camp::idx_t DIM>
+  RAJA_HOST_DEVICE RAJA_INLINE constexpr linear_index_type get_dim_size() const
+  {
+    return layout.template get_dim_size<DIM>();
+  }
+
+  template<camp::idx_t DIM>
+  RAJA_INLINE RAJA_HOST_DEVICE constexpr linear_index_type get_dim_begin() const
+  {
+    return layout.template get_dim_begin<DIM>();
+  }
+
   RAJA_HOST_DEVICE RAJA_INLINE constexpr pointer_type get_data() const
   {
     return pointer_type(data);