improve lookup time for matches_any_publishers().

rclcpp/include/rclcpp/experimental/intra_process_manager.hpp

@@ -386,6 +386,40 @@ class IntraProcessManager
     std::vector<uint64_t> take_ownership_subscriptions;
   };
 
+  /// Hash function for rmw_gid_t to enable use in unordered_map
+  struct rmw_gid_hash
+  {
+    std::size_t operator()(const rmw_gid_t & gid) const noexcept
+    {
+      // Using the FNV-1a hash algorithm on the gid data
+      constexpr std::size_t FNV_prime = 1099511628211u;
+      std::size_t result = 14695981039346656037u;
+
+      for (std::size_t i = 0; i < RMW_GID_STORAGE_SIZE; ++i) {
+        result ^= gid.data[i];
+        result *= FNV_prime;
+      }
+      return result;
+    }
+  };
+
+  /// Equality comparison for rmw_gid_t to enable use in unordered_map
+  struct rmw_gid_equal
+  {
+    bool operator()(const rmw_gid_t & lhs, const rmw_gid_t & rhs) const noexcept
+    {
+      // Compare implementation identifier first for fast rejection
+      if (lhs.implementation_identifier != rhs.implementation_identifier) {
+        return false;
+      }
+      // Compare the data bytes
+      return std::equal(
+        std::begin(lhs.data),
+        std::end(lhs.data),
+        std::begin(rhs.data));
+    }
+  };
+
   using SubscriptionMap =
     std::unordered_map<uint64_t, rclcpp::experimental::SubscriptionIntraProcessBase::WeakPtr>;
 
@@ -398,6 +432,9 @@ class IntraProcessManager
   using PublisherToSubscriptionIdsMap =
     std::unordered_map<uint64_t, SplittedSubscriptions>;
 
+  using GidToPublisherIdMap =
+    std::unordered_map<rmw_gid_t, uint64_t, rmw_gid_hash, rmw_gid_equal>;
+
   RCLCPP_PUBLIC
   static
   uint64_t
@@ -640,6 +677,7 @@ class IntraProcessManager
   SubscriptionMap subscriptions_;
   PublisherMap publishers_;
   PublisherBufferMap publisher_buffers_;
+  GidToPublisherIdMap gid_to_pub_id_;
 
   mutable std::shared_timed_mutex mutex_;
 };

rclcpp/src/rclcpp/intra_process_manager.cpp

@@ -51,6 +51,9 @@ IntraProcessManager::add_publisher(
     }
   }
 
+  // Add GID to publisher ID mapping for fast lookups
+  gid_to_pub_id_[publisher->get_gid()] = pub_id;
+
   // Initialize the subscriptions storage for this publisher.
   pub_to_subs_[pub_id] = SplittedSubscriptions();
 
@@ -98,6 +101,15 @@ IntraProcessManager::remove_publisher(uint64_t intra_process_publisher_id)
 {
   std::unique_lock<std::shared_timed_mutex> lock(mutex_);
 
+  // Remove GID to publisher ID mapping
+  auto pub_it = publishers_.find(intra_process_publisher_id);
+  if (pub_it != publishers_.end()) {
+    auto publisher = pub_it->second.lock();
+    if (publisher) {
+      gid_to_pub_id_.erase(publisher->get_gid());
+    }
+  }
+
   publishers_.erase(intra_process_publisher_id);
   publisher_buffers_.erase(intra_process_publisher_id);
   pub_to_subs_.erase(intra_process_publisher_id);
@@ -108,16 +120,20 @@ IntraProcessManager::matches_any_publishers(const rmw_gid_t * id) const
 {
   std::shared_lock<std::shared_timed_mutex> lock(mutex_);
 
-  for (auto & publisher_pair : publishers_) {
-    auto publisher = publisher_pair.second.lock();
-    if (!publisher) {
-      continue;
-    }
-    if (*publisher.get() == id) {
-      return true;
-    }
+  // Use O(1) hash map lookup instead of O(n) iteration
+  auto it = gid_to_pub_id_.find(*id);
+  if (it == gid_to_pub_id_.end()) {
+    return false;
+  }
+
+  // Verify the publisher still exists
+  auto pub_it = publishers_.find(it->second);
+  if (pub_it == publishers_.end()) {
+    return false;
   }
-  return false;
+
+  auto publisher = pub_it->second.lock();
+  return publisher != nullptr;
 }
 
 size_t

rclcpp/test/rclcpp/test_intra_process_manager.cpp

@@ -162,7 +162,14 @@ class PublisherBase
   explicit PublisherBase(const std::string & topic, const rclcpp::QoS & qos)
   : topic_name(topic),
     qos_profile(qos)
-  {}
+  {
+    // Initialize a mock GID with unique data based on this pointer
+    gid_.implementation_identifier = "mock_rmw";
+    auto ptr_value = reinterpret_cast<std::uintptr_t>(this);
+    for (size_t i = 0; i < RMW_GID_STORAGE_SIZE; ++i) {
+      gid_.data[i] = static_cast<uint8_t>((ptr_value >> (i * 8)) & 0xFF);
+    }
+  }
 
   virtual ~PublisherBase()
   {}
@@ -192,6 +199,12 @@ class PublisherBase
     return qos_profile.durability() == rclcpp::DurabilityPolicy::TransientLocal;
   }
 
+  const rmw_gid_t &
+  get_gid() const
+  {
+    return gid_;
+  }
+
   bool
   operator==([[maybe_unused]] const rmw_gid_t & gid) const
   {
@@ -210,6 +223,7 @@ class PublisherBase
 private:
   std::string topic_name;
   rclcpp::QoS qos_profile;
+  rmw_gid_t gid_;
 };
 
 template<typename T, typename Alloc = std::allocator<void>>