From 032fb7e91dfd7a5b53a0ffb31890147148c5d598 Mon Sep 17 00:00:00 2001
From: Pablo Tello <pablo.tello@arm.com>
Date: Wed, 27 Feb 2019 13:32:51 +0000
Subject: COMPMID-1766: Fixed NonMaxSuppression reference.

Change-Id: Id1cb964e35ee3e524ffa2db6b112a8cc37853124
Signed-off-by: Pablo Tello <pablo.tello@arm.com>
Reviewed-on: https://review.mlplatform.org/c/801
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>
---
 tests/validation/reference/NonMaxSuppression.cpp | 26 +++++++++++++++---------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/tests/validation/reference/NonMaxSuppression.cpp b/tests/validation/reference/NonMaxSuppression.cpp
index 75929085b3..5b7980d2f0 100644
--- a/tests/validation/reference/NonMaxSuppression.cpp
+++ b/tests/validation/reference/NonMaxSuppression.cpp
@@ -53,13 +53,14 @@ inline Box get_box(const SimpleTensor<float> &boxes, size_t id)
                get_elem_by_coordinate(boxes, Coordinates(3, id)));
 }
 
+// returns a pair (minX, minY)
 inline std::pair<float, float> get_min_yx(Box b)
 {
     return std::make_pair(
                std::min<float>(std::get<0>(b), std::get<2>(b)),
                std::min<float>(std::get<1>(b), std::get<3>(b)));
 }
-
+// returns a pair (maxX, maxY)
 inline std::pair<float, float> get_max_yx(Box b)
 {
     return std::make_pair(
@@ -96,7 +97,8 @@ inline bool reject_box(Box b0, Box b1, float threshold)
     }
     else
     {
-        return compute_intersection(b0_min, b0_max, b1_min, b1_max, b0_size, b1_size) > threshold;
+        const float box_weight = compute_intersection(b0_min, b0_max, b1_min, b1_max, b0_size, b1_size);
+        return box_weight > threshold;
     }
 }
 
@@ -111,7 +113,7 @@ inline std::vector<CandidateBox> get_candidates(const SimpleTensor<float> &score
             candidates_vector.push_back(cb);
         }
     }
-    std::sort(candidates_vector.begin(), candidates_vector.end(), [](const CandidateBox bb0, const CandidateBox bb1)
+    std::stable_sort(candidates_vector.begin(), candidates_vector.end(), [](const CandidateBox bb0, const CandidateBox bb1)
     {
         return bb0.second >= bb1.second;
     });
@@ -122,7 +124,10 @@ inline bool is_box_selected(const CandidateBox &cb, const SimpleTensor<float> &b
 {
     for(int j = selected_boxes.size() - 1; j >= 0; --j)
     {
-        if(reject_box(get_box(bboxes, cb.first), get_box(bboxes, selected_boxes[j]), threshold))
+        const auto selected_box_jth   = get_box(bboxes, selected_boxes[j]);
+        const auto candidate_box      = get_box(bboxes, cb.first);
+        const bool candidate_rejected = reject_box(candidate_box, selected_box_jth, threshold);
+        if(candidate_rejected)
         {
             return false;
         }
@@ -138,19 +143,20 @@ SimpleTensor<int> non_max_suppression(const SimpleTensor<float> &bboxes, const S
     const size_t                    output_size       = std::min(static_cast<size_t>(max_output_size), num_boxes);
     const std::vector<CandidateBox> candidates_vector = get_candidates(scores, score_threshold);
     std::vector<int>                selected;
-    size_t                          p(0);
-    while(selected.size() < output_size && p < candidates_vector.size() && selected.size() < candidates_vector.size())
+    for(const auto c : candidates_vector)
     {
-        const auto nc = candidates_vector[p++];
-        if(is_box_selected(nc, bboxes, selected, nms_threshold))
+        if(selected.size() == output_size)
+        {
+            break;
+        }
+        if(is_box_selected(c, bboxes, selected, nms_threshold))
         {
-            selected.push_back(nc.first);
+            selected.push_back(c.first);
         }
     }
     std::copy_n(selected.begin(), selected.size(), indices.data());
     return indices;
 }
-
 } // namespace reference
 } // namespace validation
 } // namespace test
-- 
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