From c3caed503a8709c1953e2c08aab5478469e67a58 Mon Sep 17 00:00:00 2001
From: Lars Glud <larshg@gmail.com>
Date: Tue, 26 Nov 2024 14:18:27 +0100
Subject: [PATCH] Remove the need for #pragma critical, by saving if a point
 should be removed in an array.

Do a second loop, to assign indexes to indices and removed_indices_.
---
 .../filters/impl/radius_outlier_removal.hpp   | 44 ++++++++-----------
 1 file changed, 19 insertions(+), 25 deletions(-)

diff --git a/filters/include/pcl/filters/impl/radius_outlier_removal.hpp b/filters/include/pcl/filters/impl/radius_outlier_removal.hpp
index 9b221959888..0e0a2b54f59 100644
--- a/filters/include/pcl/filters/impl/radius_outlier_removal.hpp
+++ b/filters/include/pcl/filters/impl/radius_outlier_removal.hpp
@@ -79,6 +79,7 @@ pcl::RadiusOutlierRemoval<PointT>::applyFilterIndices (Indices &indices)
   // The arrays to be used
   Indices nn_indices (mean_k);
   std::vector<float> nn_dists(mean_k);
+  std::vector<std::uint8_t> to_keep(indices_->size());
   indices.resize (indices_->size ());
   removed_indices_->resize (indices_->size ());
   int oii = 0, rii = 0;  // oii = output indices iterator, rii = removed indices iterator
@@ -94,7 +95,7 @@ pcl::RadiusOutlierRemoval<PointT>::applyFilterIndices (Indices &indices)
     num_threads(num_threads_)
     for (ptrdiff_t i = 0; i < static_cast<ptrdiff_t>(indices_->size()); i++)
     {
-      const index_t index = indices_->at(i);
+      const index_t& index = (*indices_)[i];
       // Perform the nearest-k search
       const int k = searcher_->nearestKSearch (index, mean_k, nn_indices, nn_dists);
 
@@ -129,22 +130,12 @@ pcl::RadiusOutlierRemoval<PointT>::applyFilterIndices (Indices &indices)
       // Unless negative was set, then it's the opposite condition
       if (!chk_neighbors)
       {
-        if (extract_removed_indices_)
-        {
-          #pragma omp critical
-          {
-            (*removed_indices_)[rii++] = index;
-          }
-        }
-          
+        to_keep[index] = 0;
         continue;
       }
 
       // Otherwise it was a normal point for output (inlier)
-      #pragma omp critical
-      {
-        indices[oii++] = index;
-      }
+      to_keep[index] = 1;
     }
   }
   // NaN or Inf values could exist => use radius search
@@ -158,7 +149,7 @@ pcl::RadiusOutlierRemoval<PointT>::applyFilterIndices (Indices &indices)
     num_threads(num_threads_)
     for (ptrdiff_t i = 0; i < static_cast<ptrdiff_t>(indices_->size()); i++)
     {
-      const index_t index = indices_->at(i);
+      const index_t& index = (*indices_)[i];
       if (!pcl::isXYFinite((*input_)[index]))
         continue;
       // Perform the radius search
@@ -170,21 +161,24 @@ pcl::RadiusOutlierRemoval<PointT>::applyFilterIndices (Indices &indices)
       // Unless negative was set, then it's the opposite condition
       if ((!negative_ && k <= min_pts_radius_) || (negative_ && k > min_pts_radius_))
       {
-        if (extract_removed_indices_)
-        {
-          #pragma omp critical
-          {
-            (*removed_indices_)[rii++] = index;
-          }
-        }
+        to_keep[index] = 0;
         continue;
       }
 
       // Otherwise it was a normal point for output (inlier)
-      #pragma omp critical
-      {
-        indices[oii++] = index;
-      }
+      to_keep[index] = 1;
+    }
+  }
+
+  for (index_t i=0; i < to_keep.size(); i++)
+  {
+    if (to_keep[i] == 1)
+    {
+      indices[oii++] = i;
+    }
+    else
+    {
+      (*removed_indices_)[rii++] = i;
     }
   }