COMPMID-1766: Implemented CPP Non Max Suppression

Change-Id: I1dcd5fb3d9ad6c6c750415bf8074698b800dfbc1
Reviewed-on: https://review.mlplatform.org/494
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Giuseppe Rossini <giuseppe.rossini@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>

1 files changed, 126 insertions, 0 deletions

diff --git a/tests/validation/reference/NonMaxSuppression.cpp b/tests/validation/reference/NonMaxSuppression.cpp
new file mode 100644
index 0000000000..013a26f645
--- /dev/null
+++ b/tests/validation/reference/NonMaxSuppression.cpp
@@ -0,0 +1,126 @@
+/*
+ * Copyright (c) 2019 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.
+ */
+#include "Permute.h"
+
+#include "arm_compute/core/Types.h"
+#include "tests/validation/Helpers.h"
+#include <queue>
+
+namespace arm_compute
+{
+namespace test
+{
+namespace validation
+{
+namespace reference
+{
+namespace
+{
+inline float get_elem_by_coordinate(const SimpleTensor<float> &tensor, Coordinates coord)
+{
+    return *static_cast<const float *>(tensor(coord));
+}
+
+// Return intersection-over-union overlap between boxes i and j
+inline bool iou_greater_than_threshold(const SimpleTensor<float> &boxes, size_t i, size_t j, float iou_threshold)
+{
+    const float ymin_i = std::min<float>(get_elem_by_coordinate(boxes, Coordinates(0, i)), get_elem_by_coordinate(boxes, Coordinates(2, i)));
+    const float xmin_i = std::min<float>(get_elem_by_coordinate(boxes, Coordinates(1, i)), get_elem_by_coordinate(boxes, Coordinates(3, i)));
+    const float ymax_i = std::max<float>(get_elem_by_coordinate(boxes, Coordinates(0, i)), get_elem_by_coordinate(boxes, Coordinates(2, i)));
+    const float xmax_i = std::max<float>(get_elem_by_coordinate(boxes, Coordinates(1, i)), get_elem_by_coordinate(boxes, Coordinates(3, i)));
+    const float ymin_j = std::min<float>(get_elem_by_coordinate(boxes, Coordinates(0, j)), get_elem_by_coordinate(boxes, Coordinates(2, j)));
+    const float xmin_j = std::min<float>(get_elem_by_coordinate(boxes, Coordinates(1, j)), get_elem_by_coordinate(boxes, Coordinates(3, j)));
+    const float ymax_j = std::max<float>(get_elem_by_coordinate(boxes, Coordinates(0, j)), get_elem_by_coordinate(boxes, Coordinates(2, j)));
+    const float xmax_j = std::max<float>(get_elem_by_coordinate(boxes, Coordinates(1, j)), get_elem_by_coordinate(boxes, Coordinates(3, j)));
+    const float area_i = (ymax_i - ymin_i) * (xmax_i - xmin_i);
+    const float area_j = (ymax_j - ymin_j) * (xmax_j - xmin_j);
+    if(area_i <= 0 || area_j <= 0)
+    {
+        return false;
+    }
+    const float intersection_ymin = std::max<float>(ymin_i, ymin_j);
+    const float intersection_xmin = std::max<float>(xmin_i, xmin_j);
+    const float intersection_ymax = std::min<float>(ymax_i, ymax_j);
+    const float intersection_xmax = std::min<float>(xmax_i, xmax_j);
+    const float intersection_area = std::max<float>(intersection_ymax - intersection_ymin, 0.0) * std::max<float>(intersection_xmax - intersection_xmin, 0.0);
+    const float iou               = intersection_area / (area_i + area_j - intersection_area);
+    return iou > iou_threshold;
+}
+
+} // namespace
+
+SimpleTensor<int> non_max_suppression(const SimpleTensor<float> &bboxes, const SimpleTensor<float> &scores, SimpleTensor<int> &indices,
+                                      unsigned int max_output_size, float score_threshold, float nms_threshold)
+{
+    const size_t       num_boxes   = bboxes.shape().y();
+    const size_t       output_size = std::min(static_cast<size_t>(max_output_size), num_boxes);
+    std::vector<float> scores_data(num_boxes);
+    std::copy_n(scores.data(), num_boxes, scores_data.begin());
+
+    using CandidateBox = std::pair<int /* index */, float /* score */>;
+    auto cmp           = [](const CandidateBox bb0, const CandidateBox bb1)
+    {
+        return bb0.second < bb1.second;
+    };
+
+    std::priority_queue<CandidateBox, std::deque<CandidateBox>, decltype(cmp)> candidate_priority_queue(cmp);
+    for(size_t i = 0; i < scores_data.size(); ++i)
+    {
+        if(scores_data[i] > score_threshold)
+        {
+            candidate_priority_queue.emplace(CandidateBox({ i, scores_data[i] }));
+        }
+    }
+
+    std::vector<int>   selected;
+    std::vector<float> selected_scores;
+    CandidateBox       next_candidate;
+
+    while(selected.size() < output_size && !candidate_priority_queue.empty())
+    {
+        next_candidate = candidate_priority_queue.top();
+        candidate_priority_queue.pop();
+        bool should_select = true;
+        for(int j = selected.size() - 1; j >= 0; --j)
+        {
+            if(iou_greater_than_threshold(bboxes, next_candidate.first, selected[j], nms_threshold))
+            {
+                should_select = false;
+                break;
+            }
+        }
+        if(should_select)
+        {
+            selected.push_back(next_candidate.first);
+            selected_scores.push_back(next_candidate.second);
+        }
+    }
+    std::copy_n(selected.begin(), selected.size(), indices.data());
+    return indices;
+}
+
+} // namespace reference
+} // namespace validation
+} // namespace test
+} // namespace arm_compute