Merge pull request #4570 from Yuki992411/ml-kmeans

[ml] Fix un-initialized centroids bug (k-means)

ml/src/kmeans.cpp

@@ -97,6 +97,10 @@ pcl::Kmeans::computeCentroids()
   for (Centroids::value_type& centroid : centroids_) {
     PointId num_points_in_cluster = 0;
 
+    // Set zero
+    for (Point::value_type& c : centroid)
+      c = 0.0;
+
     // For each PointId in this set
     for (const auto& pid : clusters_to_points_[cid]) {
       Point p = data_[pid];

test/CMakeLists.txt

@@ -43,6 +43,7 @@ add_subdirectory(gpu)
 add_subdirectory(io)
 add_subdirectory(kdtree)
 add_subdirectory(keypoints)
+add_subdirectory(ml)
 add_subdirectory(people)
 add_subdirectory(octree)
 add_subdirectory(outofcore)

test/ml/CMakeLists.txt

+set(SUBSYS_NAME tests_ml)
+set(SUBSYS_DESC "Point cloud library ml module unit tests")
+PCL_SET_TEST_DEPENDENCIES(SUBSYS_DEPS ml)
+
+set(DEFAULT ON)
+set(build TRUE)
+PCL_SUBSYS_OPTION(build "${SUBSYS_NAME}" "${SUBSYS_DESC}" ${DEFAULT} "${REASON}")
+PCL_SUBSYS_DEPEND(build "${SUBSYS_NAME}" DEPS ${SUBSYS_DEPS} OPT_DEPS ${OPT_DEPS})
+
+if(NOT build)
+  return()
+endif()
+
+PCL_ADD_TEST(ml_kmeans test_ml_kmeans FILES test_kmeans.cpp LINK_WITH pcl_gtest pcl_common pcl_ml)

test/ml/test_kmeans.cpp

+/*
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ *  Point Cloud Library (PCL) - www.pointclouds.org
+ *  Copyright (c) 2020-, Open Perception
+ *
+ *  All rights reserved
+ */
+#include <pcl/test/gtest.h>
+#include <pcl/common/random.h>
+#include <pcl/ml/kmeans.h>
+
+using namespace pcl;
+using namespace pcl::common;
+
+using Point = std::vector<float>;
+
+// Prepare random number generator in PCL
+UniformGenerator<float> engine (-100000.0, 100000.0, 2021);
+
+class SampleDataChecker
+{
+  public:
+    int data_size_;
+    int dim_;
+    int cluster_size_;
+    std::vector<Point> data_sequence_;
+    std::vector<Point> answer_centroids_;
+
+    // Create sample data
+    void
+    createDataSequence ()
+    {
+      for (int data_id = 0; data_id < data_size_; ++data_id)
+      {
+        Point data;
+        for (int dim_i = 0; dim_i < dim_; ++dim_i)
+          data.push_back (engine.run ());
+        data_sequence_.push_back (data);
+      }
+    }
+
+    void
+    testKmeans (Kmeans& k_means)
+    {
+      k_means.setClusterSize (cluster_size_);
+      k_means.setInputData (data_sequence_);
+      k_means.initialClusterPoints ();
+      k_means.computeCentroids ();
+
+      // Input centroids that should be the correct answer
+      answer_centroids_ = k_means.get_centroids ();
+
+      // If centroids_ was initialized before calculating it,
+      // then it should not change
+      // no matter how many times this class method is called.
+      k_means.computeCentroids ();
+      k_means.computeCentroids ();
+    }
+};
+
+//////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+TEST (ComputeCentroids, Case1)
+{
+  // Create sample data sequence
+  SampleDataChecker sdc;
+  sdc.data_size_ = 20;
+  sdc.dim_ = 21;
+  sdc.cluster_size_ = 9;
+  sdc.createDataSequence ();
+
+  // Compute centroids with K-means
+  Kmeans k_means (sdc.data_size_, sdc.dim_);
+  sdc.testKmeans (k_means);
+
+  // Evaluate if the two centroids are the same
+  EXPECT_EQ (sdc.cluster_size_, k_means.get_centroids ().size ());
+  EXPECT_EQ (sdc.answer_centroids_, k_means.get_centroids ());
+}
+
+//////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+TEST (ComputeCentroids, Case2)
+{
+  // Create sample data sequence
+  SampleDataChecker sdc;
+  sdc.data_size_ = 1;
+  sdc.dim_ = 1;
+  sdc.cluster_size_ = 1;
+  sdc.createDataSequence ();
+
+  // Compute centroids with K-means
+  Kmeans k_means (sdc.data_size_, sdc.dim_);
+  sdc.testKmeans (k_means);
+
+  // Evaluate if the two centroids are the same
+  EXPECT_EQ (sdc.cluster_size_, k_means.get_centroids ().size ());
+  EXPECT_EQ (sdc.answer_centroids_, k_means.get_centroids ());
+}
+
+/* ---[ */
+int
+main (int argc, char** argv)
+{
+  testing::InitGoogleTest (&argc, argv);
+  return (RUN_ALL_TESTS ());
+}
+/* ]--- */