Add blocked_nd_range class template (#555)

Signed-off-by: Tobias Weinzierl <[email protected]>
Co-authored-by: Alexey Kukanov <[email protected]>
Co-authored-by: Johannes Bockhorst <[email protected]>
Co-authored-by: Alexandra <[email protected]>

source/elements/oneTBB/source/algorithms.rst

@@ -39,6 +39,7 @@ Types that meet the :doc:`Range requirements <named_requirements/algorithms/rang
    algorithms/blocked_ranges/blocked_range_cls.rst
    algorithms/blocked_ranges/blocked_range2d_cls.rst
    algorithms/blocked_ranges/blocked_range3d_cls.rst
+   algorithms/blocked_ranges/blocked_nd_range_cls.rst
 
 .. _Partitioners:
 

source/elements/oneTBB/source/algorithms/blocked_ranges/blocked_nd_range_cls.rst

@@ -0,0 +1,179 @@
+.. SPDX-FileCopyrightText: 2019-2024 Intel Corporation
+.. SPDX-FileCopyrightText: Contributors to the oneAPI Specification project.
+..
+.. SPDX-License-Identifier: CC-BY-4.0
+
+================
+blocked_nd_range
+================
+**[algorithms.blocked_nd_range]**
+
+Class template that represents a recursively divisible N-dimensional half-open interval.
+
+A ``blocked_nd_range`` is the N-dimensional extension of ``blocked_range``.
+You can interpret it as a Cartesian product of N instances of ``blocked_range``.
+It meets the :doc:`Range requirements <../../named_requirements/algorithms/range>`.
+
+Unlike ``blocked_range2d`` and ``blocked_range3d``, all dimensions of ``blocked_nd_range`` must be specified
+over the same ``Value`` type. The class constructors also differ from those of ``blocked_range2d/3d``.
+Different naming patterns indicate the distinction between the classes.
+For example, ``blocked_nd_range<int,2>`` is analogous but not identical to ``blocked_range2d<int,int>``.
+
+.. code:: cpp
+
+    namespace oneapi {
+        namespace tbb {
+
+            template<typename Value, unsigned int N>
+            class blocked_nd_range {
+            public:
+                // Types
+                using value_type = Value;
+                using dim_range_type = blocked_range<value_type>;
+                using size_type = typename dim_range_type::size_type;
+
+                // Constructors
+                blocked_nd_range(const dim_range_type& dim0 /*, ... - exactly N parameters of the same type*/);
+                blocked_nd_range(const value_type (&dim_size)[N], size_type grainsize = 1);
+                blocked_nd_range(blocked_nd_range& r, split); 
+                blocked_nd_range(blocked_nd_range& r, proportional_split proportion); 
+
+                // Capacity
+                static constexpr unsigned int dim_count();
+                bool empty() const;
+
+                // Access
+                bool is_divisible() const;
+                const dim_range_type& dim(unsigned int dimension) const;
+            };
+
+        } // namespace tbb
+    } // namespace oneapi        
+
+Requirements:
+
+* ``N`` must be greater than 0.
+* The *Value* must meet the :doc:`BlockedRangeValue requirements <../../named_requirements/algorithms/blocked_range_val>`.
+
+Member types
+------------
+
+.. code:: cpp
+
+    using value_type = Value;
+
+The type of the range values.
+
+.. code:: cpp
+
+    using dim_range_type = blocked_range<value_type>;
+
+The type that represents one out of the N dimensions.
+
+.. code:: cpp
+
+    using size_type = typename dim_range_type::size_type;
+
+The type for measuring the size of a dimension.
+
+Member functions
+----------------
+
+.. code:: cpp
+
+    blocked_nd_range( const dim_range_type& dim0 /*, ... - exactly N parameters of the same type*/ );
+
+**Effects:**  Constructs a ``blocked_nd_range`` representing an N-dimensional space of values.
+The space is the half-open Cartesian product of one-dimensional ranges ``dim0 x ...``.
+The constructor must take exactly N arguments, which types match ``const dim_range_type&``.
+
+**Example:** For ``blocked_nd_range<int,4>``, this constructor is equivalent to
+``blocked_nd_range( const blocked_range<int>&, const blocked_range<int>&, const blocked_range<int>&, const blocked_range<int>& )``.
+
+.. note::
+    This constructor cannot be substituted with a variadic template constructor
+    ``template <typename... Dims> blocked_nd_range( const Dims&... dims )``, even if the latter
+    is constrained by the size and type requirements for the parameter pack ``Dims``.
+    That is because the types in ``Dims`` could not be automatically deduced from arguments specified as
+    braced initialization lists, and so expressions like ``blocked_nd_range<int,4>{{0,1},{0,2},{0,3},{0,4}}``
+    would fail to compile.
+
+.. code:: cpp
+
+    blocked_nd_range( const value_type (&dim_size)[N], size_type grainsize = 1 );
+
+**Effects:**  Constructs a ``blocked_nd_range`` representing an N-dimensional space of values.
+The space is the half-open Cartesian product of ranges ``[0, dim_size[0]) x [0, dim_size[1]) x ...``
+each having the same grain size.
+
+**Example:**  The ``blocked_nd_range<int,4> r( {5,6,7,8}, 4 );`` statement constructs a four-dimensional
+space that contains all value tuples ``(i, j, k, l)``, where ``i`` ranges from 0 (included)
+to 5 (excluded) with a grain size of 4, ``j`` ranges from 0 to 6 with a grain size of 4, and so forth.
+
+.. code:: cpp
+
+    blocked_nd_range( blocked_nd_range& range, split );
+
+Basic splitting constructor.
+
+**Requirements**: ``is_divisible()`` is true.
+
+**Effects**: Partitions ``range`` into two subranges. The newly constructed ``blocked_nd_range`` is approximately
+the half of the original ``range``, and ``range`` is updated to be the remainder.
+Splitting is done across one dimension, while other dimensions and the grain sizes for
+each subrange remain the same as in the original ``range``.
+
+.. note::
+    It is recommended to split across the dimension with the biggest size-to-grainsize ratio,
+    so that, after repeated splitting, subranges become of approximately square/cubic/hypercubic shape
+    if all grain sizes are the same.
+
+.. code:: cpp
+
+    blocked_nd_range( blocked_nd_range& range, proportional_split proportion );
+
+Proportional splitting constructor.
+
+**Requirements**: ``is_divisible()`` is true.
+
+**Effects**: Partitions ``range`` into two subranges in the given ``proportion`` across one of its dimensions.
+The effect is similar to the basic splitting constructor, except for proportional splitting of the selected
+dimension, as specified for :doc:`blocked_range <blocked_range_cls>`.
+Other dimensions and the grain sizes for each subrange remain the same as in the original ``range``.
+
+.. code:: cpp
+
+   static constexpr unsigned int dim_count();
+
+**Returns:** The number of dimensions set by the class template argument ``N``.
+
+.. code:: cpp
+
+    bool empty() const;
+
+**Effects**: Determines if the range is empty.
+
+**Returns:** True if for any of the range dimensions ``empty()`` is true; false, otherwise.
+
+.. code:: cpp
+
+    bool is_divisible() const;
+
+**Effects**: Determines if the range can be split into subranges.
+
+**Returns:** True if for any of the range dimensions ``is_divisible()`` is true; false, otherwise.
+
+.. code:: cpp
+
+    const dim_range_type& dim(unsigned int dimension) const;
+
+**Requirements**: 0 <= ``dimension`` < N.
+
+**Returns:** ``blocked_range`` containing the value space along the dimension specified by the argument.
+
+See also:
+
+* :doc:`blocked_range <blocked_range_cls>`
+* :doc:`blocked_range2d <blocked_range2d_cls>`
+* :doc:`blocked_range3d <blocked_range3d_cls>`
+

source/elements/oneTBB/source/algorithms/split_tags/proportional_split_cls.rst

@@ -19,6 +19,7 @@ the class should be split.
     // Defined in header <oneapi/tbb/blocked_range.h>
     // Defined in header <oneapi/tbb/blocked_range2d.h>
     // Defined in header <oneapi/tbb/blocked_range3d.h>
+    // Defined in header <oneapi/tbb/blocked_nd_range.h>
     // Defined in header <oneapi/tbb/partitioner.h>
     // Defined in header <oneapi/tbb/parallel_for.h>
     // Defined in header <oneapi/tbb/parallel_reduce.h>

source/elements/oneTBB/source/algorithms/split_tags/split_cls.rst

@@ -15,6 +15,7 @@ An argument of type ``split`` is used to distinguish a splitting constructor fro
     // Defined in header <oneapi/tbb/blocked_range.h>
     // Defined in header <oneapi/tbb/blocked_range2d.h>
     // Defined in header <oneapi/tbb/blocked_range3d.h>
+    // Defined in header <oneapi/tbb/blocked_nd_range.h>
     // Defined in header <oneapi/tbb/partitioner.h>
     // Defined in header <oneapi/tbb/parallel_for.h>
     // Defined in header <oneapi/tbb/parallel_reduce.h>

source/elements/oneTBB/source/named_requirements/algorithms/blocked_range_val.rst

@@ -52,5 +52,6 @@ See also:
 * :doc:`blocked_range class <../../algorithms/blocked_ranges/blocked_range_cls>`
 * :doc:`blocked_range2d class <../../algorithms/blocked_ranges/blocked_range2d_cls>`
 * :doc:`blocked_range3d class <../../algorithms/blocked_ranges/blocked_range3d_cls>`
+* :doc:`blocked_nd_range class <../../algorithms/blocked_ranges/blocked_nd_range_cls>`
 * :doc:`parallel_reduce algorithm <../../algorithms/functions/parallel_reduce_func>`
 * :doc:`parallel_for algorithm <../../algorithms/functions/parallel_for_func>`

source/elements/oneTBB/source/named_requirements/algorithms/range.rst

@@ -69,6 +69,7 @@ See also:
 * :doc:`blocked_range class <../../algorithms/blocked_ranges/blocked_range_cls>`
 * :doc:`blocked_range2d class <../../algorithms/blocked_ranges/blocked_range2d_cls>`
 * :doc:`blocked_range3d class <../../algorithms/blocked_ranges/blocked_range3d_cls>`
+* :doc:`blocked_nd_range class <../../algorithms/blocked_ranges/blocked_nd_range_cls>`
 * :doc:`parallel_reduce algorithm <../../algorithms/functions/parallel_reduce_func>`
 * :doc:`parallel_for algorithm <../../algorithms/functions/parallel_for_func>`
 * :doc:`split class <../../algorithms/split_tags/split_cls>`