From a1c1ef17c7eb4b1fc203e42e938821d92ff6a70c Mon Sep 17 00:00:00 2001
From: Dominic Koepke <koepke@aunovis.de>
Date: Fri, 14 Apr 2023 14:16:44 +0200
Subject: [PATCH 1/4] mark container emplacement as critical section

---
 cpp/open3d/geometry/ISSKeypoints.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/cpp/open3d/geometry/ISSKeypoints.cpp b/cpp/open3d/geometry/ISSKeypoints.cpp
index 39f8602a737..940234f8976 100644
--- a/cpp/open3d/geometry/ISSKeypoints.cpp
+++ b/cpp/open3d/geometry/ISSKeypoints.cpp
@@ -118,6 +118,7 @@ std::shared_ptr<PointCloud> ComputeISSKeypoints(
 
             if (nb_neighbors >= min_neighbors &&
                 IsLocalMaxima(i, nn_indices, third_eigen_values)) {
+#pragma omp critical
                 kp_indices.emplace_back(i);
             }
         }

From 2f5f39ea9747208a8036eba4e57fba68cc526975 Mon Sep 17 00:00:00 2001
From: Dominic Koepke <koepke@aunovis.de>
Date: Fri, 14 Apr 2023 14:42:26 +0200
Subject: [PATCH 2/4] fix: explicitly check for more than 2 found indices

---
 cpp/open3d/geometry/ISSKeypoints.cpp | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/cpp/open3d/geometry/ISSKeypoints.cpp b/cpp/open3d/geometry/ISSKeypoints.cpp
index 940234f8976..92222a970bf 100644
--- a/cpp/open3d/geometry/ISSKeypoints.cpp
+++ b/cpp/open3d/geometry/ISSKeypoints.cpp
@@ -11,8 +11,10 @@
 
 #include <Eigen/Core>
 #include <Eigen/Eigenvalues>
+#include <algorithm>
 #include <cmath>
 #include <memory>
+#include <numeric>
 #include <tuple>
 #include <vector>
 
@@ -41,15 +43,20 @@ double ComputeModelResolution(const std::vector<Eigen::Vector3d>& points,
                               const geometry::KDTreeFlann& kdtree) {
     std::vector<int> indices(2);
     std::vector<double> distances(2);
-    double resolution = 0.0;
+    const double resolution = std::accumulate(
+        points.begin(),
+        points.end(),
+        0.,
+        [&](double state, const Eigen::Vector3d& point) {
+            if (kdtree.SearchKNN(point, 2, indices, distances) >= 2) {
+                state += std::sqrt(distances[1]);
+            }
 
-    for (const auto& point : points) {
-        if (kdtree.SearchKNN(point, 2, indices, distances) != 0) {
-            resolution += std::sqrt(distances[1]);
+            return state;
         }
-    }
-    resolution /= points.size();
-    return resolution;
+    );
+
+    return resolution / static_cast<double>(points.size());
 }
 
 }  // namespace

From 85d39deacd76669e3cd99efa3ae8775e2a05fb61 Mon Sep 17 00:00:00 2001
From: Dominic Koepke <koepke@aunovis.de>
Date: Fri, 14 Apr 2023 14:47:00 +0200
Subject: [PATCH 3/4] refactor: utilize none_of algorithm in IsLocalMaxima

---
 cpp/open3d/geometry/ISSKeypoints.cpp | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/cpp/open3d/geometry/ISSKeypoints.cpp b/cpp/open3d/geometry/ISSKeypoints.cpp
index 92222a970bf..e17839edeaf 100644
--- a/cpp/open3d/geometry/ISSKeypoints.cpp
+++ b/cpp/open3d/geometry/ISSKeypoints.cpp
@@ -31,12 +31,13 @@ namespace {
 bool IsLocalMaxima(int query_idx,
                    const std::vector<int>& indices,
                    const std::vector<double>& third_eigen_values) {
-    for (const auto& idx : indices) {
-        if (third_eigen_values[query_idx] < third_eigen_values[idx]) {
-            return false;
+    return std::none_of(
+        indices.begin(),
+        indices.end(),
+        [&third_eigen_values, value = third_eigen_values[query_idx]](const int idx) {
+            return value < third_eigen_values[idx];
         }
-    }
-    return true;
+    );
 }
 
 double ComputeModelResolution(const std::vector<Eigen::Vector3d>& points,
@@ -51,7 +52,6 @@ double ComputeModelResolution(const std::vector<Eigen::Vector3d>& points,
             if (kdtree.SearchKNN(point, 2, indices, distances) >= 2) {
                 state += std::sqrt(distances[1]);
             }
-
             return state;
         }
     );

From 219dfbc5bf2e06fb9900edfae73aad43d6d8af85 Mon Sep 17 00:00:00 2001
From: Benjamin Ummenhofer <benjamin.ummenhofer@intel.com>
Date: Fri, 30 Jun 2023 10:54:34 +0200
Subject: [PATCH 4/4] apply style

---
 cpp/open3d/geometry/ISSKeypoints.cpp | 26 ++++++++++----------------
 1 file changed, 10 insertions(+), 16 deletions(-)

diff --git a/cpp/open3d/geometry/ISSKeypoints.cpp b/cpp/open3d/geometry/ISSKeypoints.cpp
index e17839edeaf..f47abae1ad2 100644
--- a/cpp/open3d/geometry/ISSKeypoints.cpp
+++ b/cpp/open3d/geometry/ISSKeypoints.cpp
@@ -32,12 +32,9 @@ bool IsLocalMaxima(int query_idx,
                    const std::vector<int>& indices,
                    const std::vector<double>& third_eigen_values) {
     return std::none_of(
-        indices.begin(),
-        indices.end(),
-        [&third_eigen_values, value = third_eigen_values[query_idx]](const int idx) {
-            return value < third_eigen_values[idx];
-        }
-    );
+            indices.begin(), indices.end(),
+            [&third_eigen_values, value = third_eigen_values[query_idx]](
+                    const int idx) { return value < third_eigen_values[idx]; });
 }
 
 double ComputeModelResolution(const std::vector<Eigen::Vector3d>& points,
@@ -45,16 +42,13 @@ double ComputeModelResolution(const std::vector<Eigen::Vector3d>& points,
     std::vector<int> indices(2);
     std::vector<double> distances(2);
     const double resolution = std::accumulate(
-        points.begin(),
-        points.end(),
-        0.,
-        [&](double state, const Eigen::Vector3d& point) {
-            if (kdtree.SearchKNN(point, 2, indices, distances) >= 2) {
-                state += std::sqrt(distances[1]);
-            }
-            return state;
-        }
-    );
+            points.begin(), points.end(), 0.,
+            [&](double state, const Eigen::Vector3d& point) {
+                if (kdtree.SearchKNN(point, 2, indices, distances) >= 2) {
+                    state += std::sqrt(distances[1]);
+                }
+                return state;
+            });
 
     return resolution / static_cast<double>(points.size());
 }