Add support for arbitrary parameters for CPU Gather

* The shape of input and indices tensors, and the gather axis
  can be any number, as long as these are valid and the output
  tensor doesn't have more dimensions than the library supports.
* Update the reference code to be more generic and straightforward.
* Add necessary test cases.

Signed-off-by: Viet-Hoa Do <viet-hoa.do@arm.com>
Resolves: COMPMID-5919
Change-Id: Ic7e2032777aa97ecc147f61d5388528697508ab1
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/9199
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Gunes Bayir <gunes.bayir@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Benchmark: Arm Jenkins <bsgcomp@arm.com>

1 files changed, 28 insertions, 46 deletions

diff --git a/tests/validation/reference/Gather.cpp b/tests/validation/reference/Gather.cpp
index 8de1a473eb..12d1a3cd3c 100644
--- a/tests/validation/reference/Gather.cpp
+++ b/tests/validation/reference/Gather.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2019, 2022 Arm Limited.
+ * Copyright (c) 2018-2019, 2022-2023 Arm Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -39,61 +39,43 @@ namespace reference
 template <typename T>
 SimpleTensor<T> gather(const SimpleTensor<T> &src, const SimpleTensor<uint32_t> &indices, uint32_t actual_axis)
 {
-    const auto       *indices_ptr = static_cast<const uint32_t *>(indices.data());
     const TensorShape dst_shape   = arm_compute::misc::shape_calculator::compute_gather_shape(src.shape(), indices.shape(), actual_axis);
     SimpleTensor<T>   dst(dst_shape, src.data_type());
 
+    const auto        src_ptr     = static_cast<const T *>(src.data());
+    const auto        indices_ptr = static_cast<const uint32_t *>(indices.data());
+    const auto        dst_ptr     = static_cast<T *>(dst.data());
+
     Window win;
     win.use_tensor_dimensions(dst_shape);
-    if(indices.shape().num_dimensions() == 1u)
-    {
-        execute_window_loop(win, [&](const Coordinates & id)
+
+    execute_window_loop(win, [&](const Coordinates &dst_coords) {
+        // Calculate the coordinates of the index value.
+        Coordinates idx_coords;
+
+        for(size_t i = 0; i < indices.shape().num_dimensions(); ++i)
         {
-            Coordinates offset;
-            for(unsigned int dim = 0; dim < id.num_dimensions(); ++dim)
-            {
-                if(dim == actual_axis)
-                {
-                    offset.set(dim, indices_ptr[id[dim]]);
-                }
-                else
-                {
-                    offset.set(dim, id[dim]);
-                }
-            }
-            *reinterpret_cast<T *>(dst(id)) = *reinterpret_cast<const T *>(src(offset));
-        });
-    }
-    else
-    {
-        if(actual_axis == 1)
+            idx_coords.set(i, dst_coords[i + actual_axis]);
+        }
+
+        // Calculate the coordinates of the source data.
+        Coordinates src_coords;
+
+        for(size_t i = 0; i < actual_axis; ++i)
         {
-            win.set(Window::DimX, Window::Dimension(0, 1, 1));
-            execute_window_loop(win, [&](const Coordinates & id)
-            {
-                auto       *dst_ptr = dst(id);
-                Coordinates index_offset;
-                for(uint32_t k = 0; k < indices.shape().num_dimensions(); ++k)
-                {
-                    index_offset.set(k, id[k + 1]);
-                }
-                const uint32_t row = *reinterpret_cast<const uint32_t *>(indices(index_offset));
-                Coordinates    src_offset;
-                src_offset.set(0, 0);
-                src_offset.set(1, row);
-                for(uint32_t j = 2; j < src.shape().num_dimensions(); ++j)
-                {
-                    src_offset.set(j, id[1 + indices.shape().num_dimensions() + (j - 2)]);
-                }
-                const auto in_ptr_row = src(src_offset);
-                memcpy(dst_ptr, in_ptr_row, src.shape()[0] * src.element_size());
-            });
+            src_coords.set(i, dst_coords[i]);
         }
-        else
+
+        src_coords.set(actual_axis, indices_ptr[coords2index(indices.shape(), idx_coords)]);
+
+        for(size_t i = actual_axis + 1; i < src.shape().num_dimensions(); ++i)
         {
-            ARM_COMPUTE_ERROR("Not implemented.");
+            src_coords.set(i, dst_coords[i + indices.shape().num_dimensions() - 1]);
         }
-    }
+
+        // Copy the data.
+        dst_ptr[coords2index(dst.shape(), dst_coords)] = src_ptr[coords2index(src.shape(), src_coords)];
+    });
 
     return dst;
 }