use simple deleted flag instead of tracking inactive indices

removing Property_container::reserve as it basically adds inactive indices and thus means linear insertion time

Property_map/include/CGAL/Property_container.h

@@ -248,6 +248,7 @@ class Property_container {
 
   std::multimap<std::string, std::shared_ptr<Property_array_base<Index>>> m_properties;
   std::vector<bool> m_active_indices{};
+  bool m_has_deleted_elements = false;
 
 public:
 
@@ -258,6 +259,7 @@ public:
 
   Property_container(const Property_container<Index>& other) {
     m_active_indices = other.m_active_indices;
+    m_has_deleted_elements = other.m_has_deleted_elements;
 
     for (auto [name, array] : other.m_properties) {
       // todo: this could probably be made faster using emplace_hint
@@ -273,6 +275,7 @@ public:
   // This is not exactly an assignment as existing unique properties are kept.
   Property_container<Index>& operator=(const Property_container<Index>& other) {
     m_active_indices = other.m_active_indices;
+    m_has_deleted_elements = other.m_has_deleted_elements;
 
     for (auto [name, array] : other.m_properties) {
       // search if property already exists
@@ -295,6 +298,7 @@ public:
   // This is not exactly an assignment as existing unique properties are kept.
   Property_container<Index>& operator=(Property_container<Index>&& other) {
     m_active_indices = std::move(other.m_active_indices);
+    m_has_deleted_elements = other.m_has_deleted_elements;
 
     for (auto [name, array] : other.m_properties) {
       // search if property already exists
@@ -312,7 +316,7 @@ public:
     }
 
     // The moved-from property map should retain all of its properties, but contain 0 elements
-    other.reserve(0);
+    other.resize(0);
     return *this;
   }
 
@@ -441,16 +445,15 @@ public:
   }*/
 
 public:
-
-  void reserve(std::size_t n) {
-    m_active_indices.resize(n);
-    for (auto [name, array]: m_properties)
-      array->reserve(n);
-  }
-
   void resize(std::size_t n) {
-    reserve(n);
+
+    m_active_indices.resize(n);
+    for (auto [name, array] : m_properties)
+      array->reserve(n);
+
     std::fill(m_active_indices.begin(), m_active_indices.end(), true);
+
+    m_has_deleted_elements = false;
   }
 
   [[nodiscard]] std::size_t size() const { return std::count(m_active_indices.begin(), m_active_indices.end(), true); }
@@ -460,8 +463,11 @@ public:
   Index emplace_back() {
 
     // Expand the storage and return the last element
-    reserve(capacity() + 1);
-    m_active_indices.back() = true;
+    m_active_indices.push_back(true);
+
+    for (auto [name, array] : m_properties)
+      array->reserve(capacity());
+
     auto first_new_index = Index(capacity() - 1);
     reset(first_new_index);
     return first_new_index;
@@ -469,6 +475,9 @@ public:
 
   Index emplace() {
 
+    if (!m_has_deleted_elements)
+      return emplace_back();
+
     // If there are empty slots, return the index of one of them and mark it as full
     auto first_unused = std::find_if(m_active_indices.begin(), m_active_indices.end(), [](bool used) { return !used; });
     if (first_unused != m_active_indices.end()) {
@@ -478,20 +487,27 @@ public:
       return index;
     }
 
+    m_has_deleted_elements = false;
+
     return emplace_back();
   }
 
   Index emplace_group_back(std::size_t n) {
 
     // Expand the storage and return the start of the new region
-    reserve(capacity() + n);
-    for (auto it = m_active_indices.end() - n; it < m_active_indices.end(); ++it)
-      *it = true;
+    m_active_indices.resize(capacity() + n, true);
+
+    for (auto [name, array] : m_properties)
+      array->reserve(capacity());
+
     return Index(capacity() - n);
   }
 
   Index emplace_group(std::size_t n) {
 
+    if (!m_has_deleted_elements)
+      return emplace_group_back(n);
+
     auto search_start = m_active_indices.begin();
     while (search_start != m_active_indices.end()) {
 
@@ -544,6 +560,7 @@ public:
 
   void erase(Index i) {
     m_active_indices[i] = false;
+    m_has_deleted_elements = true;
     for (auto [name, array]: m_properties)
       array->reset(i);
   }

Property_map/test/Property_map/test_Property_container.cpp

@@ -41,11 +41,6 @@ void test_element_access() {
 
   auto& integers = properties.add_property("integers", 5);
 
-  // Reserve space for 100 elements
-  properties.reserve(100);
-  assert(properties.capacity() == 100);
-  assert(properties.size() == 0);
-
   // Newly emplaced elements should go at the front
   assert(properties.emplace() == 0);
   assert(properties.emplace() == 1);
@@ -61,7 +56,6 @@ void test_element_access() {
   auto& floats = properties.add_property("floats", 6.0f);
 
   // The new property array should already be of the right size
-  assert(floats.capacity() == 100);
   assert(properties.size() == 3);
 
   // Pre-existing elements should contain the default value
@@ -87,9 +81,8 @@ void test_element_access() {
   // Erase an element, and the size should be reduced
   properties.erase(1);
   assert(properties.size() == 2);
-  assert(properties.capacity() == 100);
   assert(properties.active_list().size() == 2);
-  assert(properties.inactive_list().size() == 98);
+  assert(properties.inactive_list().size() == 1);
 
   // A newly emplaced element should take the empty slot
   assert(properties.emplace() == 1);