Optimize vote distribution between PRs and non-PRs (#4766)

* Publish votes to all PRs and a subset of non PRs

This avoids potential duplicate votes to PRs and better confirmation times for non PRs

* small optimisation for list_non_pr

---------

Co-authored-by: gr0vity-dev <homebot@users.noreply.github.com>

nano/node/network.cpp

@@ -281,6 +281,15 @@ void nano::network::flood_vote (std::shared_ptr<nano::vote> const & vote, float
 	}
 }
 
+void nano::network::flood_vote_non_pr (std::shared_ptr<nano::vote> const & vote, float scale, bool rebroadcasted)
+{
+	nano::confirm_ack message{ node.network_params.network, vote, rebroadcasted };
+	for (auto & i : list_non_pr (fanout (scale)))
+	{
+		i->send (message, nullptr);
+	}
+}
+
 void nano::network::flood_vote_pr (std::shared_ptr<nano::vote> const & vote, bool rebroadcasted)
 {
 	nano::confirm_ack message{ node.network_params.network, vote, rebroadcasted };
@@ -377,11 +386,13 @@ std::deque<std::shared_ptr<nano::transport::channel>> nano::network::list_non_pr
 {
 	std::deque<std::shared_ptr<nano::transport::channel>> result;
 	tcp_channels.list (result);
+
+	auto partition_point = std::partition (result.begin (), result.end (),
+	[this] (std::shared_ptr<nano::transport::channel> const & channel) {
+		return !node.rep_crawler.is_pr (channel);
+	});
+	result.resize (std::distance (result.begin (), partition_point));
 	nano::random_pool_shuffle (result.begin (), result.end ());
-	result.erase (std::remove_if (result.begin (), result.end (), [this] (std::shared_ptr<nano::transport::channel> const & channel) {
-		return node.rep_crawler.is_pr (channel);
-	}),
-	result.end ());
 	if (result.size () > count_a)
 	{
 		result.resize (count_a, nullptr);

nano/node/network.hpp

@@ -95,6 +95,7 @@ public:
 	void flood_keepalive_self (float const scale_a = 0.5f);
 	void flood_vote (std::shared_ptr<nano::vote> const &, float scale, bool rebroadcasted = false);
 	void flood_vote_pr (std::shared_ptr<nano::vote> const &, bool rebroadcasted = false);
+	void flood_vote_non_pr (std::shared_ptr<nano::vote> const &, float scale, bool rebroadcasted = false);
 	// Flood block to all PRs and a random selection of non-PRs
 	void flood_block_initial (std::shared_ptr<nano::block> const &);
 	// Flood block to a random selection of peers

nano/node/vote_generator.cpp

@@ -277,7 +277,7 @@ void nano::vote_generator::vote (std::vector<nano::block_hash> const & hashes_a,
 void nano::vote_generator::broadcast_action (std::shared_ptr<nano::vote> const & vote_a) const
 {
 	network.flood_vote_pr (vote_a);
-	network.flood_vote (vote_a, 2.0f);
+	network.flood_vote_non_pr (vote_a, 2.0f);
 	vote_processor.vote (vote_a, inproc_channel);
 }