COMPMID-1379: Created WindowIterator and TensorAccessor

- WindowIterator: used to iterate over arbitrary positions of a window. (More flexible than execute_window_loop which only can iterate over entire dimensions)
- TensorAccessor: RSH's code uses pointers to specialised types and strides in element sizes, this helps interfacing with their code.

Change-Id: I8ded8758d345668804873409f949b8cec694d289
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/139082
Tested-by: Jenkins <bsgcomp@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>

1 files changed, 292 insertions, 0 deletions

diff --git a/arm_compute/core/WindowIterator.h b/arm_compute/core/WindowIterator.h
new file mode 100644
index 0000000000..13e9973506
--- /dev/null
+++ b/arm_compute/core/WindowIterator.h
@@ -0,0 +1,292 @@
+/*
+ * Copyright (c) 2018 ARM Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+#ifndef __ARM_COMPUTE_WINDOW_ITERATOR_H__
+#define __ARM_COMPUTE_WINDOW_ITERATOR_H__
+#include "arm_compute/core/Coordinates.h"
+#include "arm_compute/core/ITensor.h"
+#include "arm_compute/core/Window.h"
+
+//FIXME: Delete the "PRINTF" before the release. In the meantime it's probably going to be useful to debug
+//#define PRINTF printf
+#define PRINTF(...)
+
+namespace arm_compute
+{
+/** Convert an offset in window steps into absolute coordinates.
+ *
+ * @param[in] w      Window @p offset is related to.
+ * @param[in] offset Offset inside the window expressed in number of window steps.
+ *
+ * @return Absolute coordinates.
+ */
+inline Coordinates convert_window_coord_to_position(const Window &w, const Coordinates &offset)
+{
+    Coordinates position;
+    for(unsigned int i = 0; i < Coordinates::num_max_dimensions; ++i)
+    {
+        position.set(i, w[i].start() + offset[i] * w[i].step());
+    }
+    return position;
+}
+
+/** Tensor accessors to make it easier to interface with arm_gemm */
+template <typename T>
+class TensorAccessor
+{
+public:
+    /** Constructor:
+     *
+     * @param[in] tensor Source tensor, must be allocated.
+     */
+    TensorAccessor(const ITensor &tensor)
+        : _first(tensor.ptr_to_element(Coordinates())), _strides(tensor.info()->strides_in_bytes())
+    {
+    }
+    /** Get the stride of the dimension dim expressed in number of Ts.
+     *
+     * @param[in] dim Dimension of the wanted stride.
+     *
+     * @return Stride in number of Ts.
+     */
+    inline size_t stride(size_t dim) const
+    {
+        return _strides[dim] / sizeof(T);
+    }
+
+    /** Returns a pointer to the element at coordinates (x,y,z,w)
+     *
+     * @param[in] x X coordinates
+     * @param[in] y (optional) Y coordinates
+     * @param[in] z (optional) Z coordinates
+     * @param[in] w (optional) W coordinates
+     */
+    inline T *get_ptr(unsigned int x, unsigned int y = 0, unsigned int z = 0, unsigned int w = 0)
+    {
+        return reinterpret_cast<T *>(_first + x * _strides[0] + y * _strides[1] + z * _strides[2] + w * _strides[3]);
+    }
+
+    /** Returns a pointer to the element at coordinates (x,y,z,w)
+     *
+     * @param[in] x X coordinates
+     * @param[in] y (optional) Y coordinates
+     * @param[in] z (optional) Z coordinates
+     * @param[in] w (optional) W coordinates
+     */
+    inline T *operator()(unsigned int x, unsigned int y = 0, unsigned int z = 0, unsigned int w = 0)
+    {
+        return get_ptr(x, y, z, w);
+    }
+
+private:
+    uint8_t       *_first;   /**< Pointer to the first element of the tensor.*/
+    const Strides &_strides; /**< Strides in bytes of the tensor */
+};
+
+/** Iterate over a portion of a Window */
+template <typename L>
+class WindowIterator
+{
+public:
+    /** Construct a WindowIterator object
+     *
+     * @param[in] w               Window to use for the iteration
+     * @param[in] start           Where to start iterating from (In Window coordinates)
+     * @param[in] end             Where to stop iterating (In Window coordinates).
+     * @param[in] lambda_function Lambda function to call for every iteration between start and end. (It will be called last for end - 1)
+     */
+    WindowIterator(const Window &w, const Coordinates &start, const Coordinates &end, L &&lambda_function)
+        : _lambda_function(std::move(lambda_function)),
+          _position(convert_window_coord_to_position(w, start)),
+          _end(convert_window_coord_to_position(w, end)),
+          _w(w)
+    {
+    }
+    /** Iterate over the lowest 3 dimensions of the window.
+     *
+     * @param[in] on_new_row_size Callback to be called before lambda_function every time the width of the row processed changes.
+     */
+    template <typename M>
+    void iterate_3D(M &&on_new_row_size)
+    {
+        while(_end.z() != _position.z())
+        {
+            PRINTF("New slice %d\n", _position.z());
+            iterate_2D_internal(on_new_row_size, _w.x().end() - _w.x().step(), _w.y().end() - _w.y().step());
+            _position[2] += _w.z().step();
+            _position[1] = _w.y().start();
+            _position[0] = _w.x().start();
+        }
+        // Left over:
+        PRINTF("Left over slice\n");
+        iterate_2D(on_new_row_size);
+    }
+
+    /** Iterate over the lowest 2 dimensions of the window.
+     *
+     * @param[in] on_new_row_size Callback to be called before lambda_function every time the width of the row processed changes.
+     */
+    template <typename M>
+    void iterate_2D(M &&on_new_row_size)
+    {
+        iterate_2D_internal(on_new_row_size, _end.x(), _end.y());
+    }
+
+    /** Change the step used for the iteration.
+     *
+     * @note Does not affect the start and end points.
+     *
+     * @param[in] dim  Dimension to change
+     * @param[in] step New step to use for the given dimension.
+     */
+    inline void set_step(size_t dim, int step)
+    {
+        _w.set_dimension_step(dim, step);
+    }
+
+    /** Returns the coordinates in absolute coordinates of the end position
+         *
+         * @return End position coordinates.
+         */
+    const Coordinates &end_position() const
+    {
+        return _end;
+    }
+
+private:
+    template <typename M>
+    void iterate_2D_internal(M &&on_new_row_size, int end_x, int end_y)
+    {
+        //Is there more than one row to process ?
+        if(end_y == _position.y())
+        {
+            // Single row:
+            PRINTF("Partial row only\n");
+            // Both start and end belong to the same row:
+            iterate_over_dim0(end_x + _w.x().step(), on_new_row_size);
+        }
+        else
+        {
+            // Do we start from the beginning of the row ?
+            if(_w.x().start() != _position.x())
+            {
+                //Start in the middle of a row: process left-over X
+                PRINTF("Partial row first\n");
+                iterate_over_dim0(_w.x().end(), on_new_row_size);
+                _position[1] += _w.y().step();
+            }
+
+            //Middle rows
+            bool no_leftover = end_x + _w.x().step() == _w.x().end();
+            if(no_leftover)
+            {
+                PRINTF("no left over\n");
+                //Switch to full row size:
+                on_new_row_size(_w[0].start(), _w.x().end());
+                // Shouldn't be possible to reach that point and not have at least one entire row to process
+                ARM_COMPUTE_ERROR_ON(_w.y().end() == _position.y());
+                // No leftover: all the rows lefts to process are full width:
+                iterate_over_dim1(_w.y().end());
+            }
+            else
+            {
+                PRINTF("with left over\n");
+                // Are there full rows to process ?
+                if(_position[1] != end_y)
+                {
+                    PRINTF("full rows\n");
+                    //Switch to full row size:
+                    on_new_row_size(_w[0].start(), _w.x().end());
+                    iterate_over_dim1(_w.y().end() - _w.y().step());
+                }
+
+                PRINTF("Final leftover\n");
+                //Leftover end x
+                _position[0] = _w.x().start();
+                iterate_over_dim0(end_x + _w.x().step(), on_new_row_size);
+            }
+        }
+    }
+
+    /** Process full rows below 'end'
+     *
+     * @param[in] end Y position to stop at.
+     */
+    void iterate_over_dim1(int end)
+    {
+        for(; _position[1] != end; _position[1] += _w[1].step())
+        {
+            _position[0] = _w[0].start();
+            iterate_over_dim0(_w[0].end());
+        }
+    }
+
+    /** Process elements of a given row up to 'end'
+     *
+     * @param[in] end             X position to stop at.
+     * @param[in] on_new_row_size Callback to call before starting iterating
+     */
+    template <typename M>
+    void iterate_over_dim0(int end, M &&on_new_row_size)
+    {
+        on_new_row_size(_position.x(), end);
+        iterate_over_dim0(end);
+    }
+
+    /** Process elements of a given row up to 'end'
+     *
+     * @param[in] end X position to stop at.
+     */
+    void iterate_over_dim0(int end)
+    {
+        PRINTF("X [%d, %d, %d]\n", _position.x(), end, _w[0].step());
+        // Both start and end belong to the same row:
+        ARM_COMPUTE_ERROR_ON(_position[0] > end);
+        for(; _position.x() < end; _position[0] += _w[0].step())
+        {
+            _lambda_function(_position);
+        }
+    }
+
+    L           _lambda_function; /**< Function to call for each iteration */
+    Coordinates _position;        /**< Absolute coordinates of the current position */
+    Coordinates _end;             /**< Absolute coordinates of the point after the last iteration */
+    Window      _w;               /**< Window to iterate over */
+};
+
+/** Create a WindowIterator object
+ *
+ * @param[in] w               Window to use for the iteration
+ * @param[in] start           Where to start iterating from (In Window coordinates)
+ * @param[in] end             Where to stop iterating (In Window coordinates).
+ * @param[in] lambda_function Lambda function to call for every iteration between start and end. (It will be called last for end - 1)
+ *
+ * @return A WindowIterator object.
+ */
+template <typename L>
+WindowIterator<L> create_window_iterator(const Window &w, const Coordinates &start, const Coordinates &end, L &&lambda_function)
+{
+    return WindowIterator<L>(w, start, end, std::move(lambda_function));
+}
+}
+#endif /*__ARM_COMPUTE_WINDOW_ITERATOR_H__*/