From a33b1691f11316f839ddfdf51e1950acf0bc08aa Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Fri, 9 Sep 2016 13:56:03 +0200
Subject: [PATCH] Do not fully sort all nodes for addr relay

As we only need 1 or 2, explicitly keep track of the best ones.
---
 src/main.cpp | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index 44031e69e7..f5e94d8ec7 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4804,26 +4804,35 @@ static void RelayTransaction(const CTransaction& tx, CConnman& connman)
 
 static void RelayAddress(const CAddress& addr, bool fReachable, CConnman& connman)
 {
-    int nRelayNodes = fReachable ? 2 : 1; // limited relaying of addresses outside our network(s)
+    unsigned int nRelayNodes = fReachable ? 2 : 1; // limited relaying of addresses outside our network(s)
 
     // Relay to a limited number of other nodes
     // Use deterministic randomness to send to the same nodes for 24 hours
     // at a time so the addrKnowns of the chosen nodes prevent repeats
     uint64_t hashAddr = addr.GetHash();
-    std::multimap<uint64_t, CNode*> mapMix;
     const CSipHasher hasher = connman.GetDeterministicRandomizer(RANDOMIZER_ID_ADDRESS_RELAY).Write(hashAddr << 32).Write((GetTime() + hashAddr) / (24*60*60));
     FastRandomContext insecure_rand;
 
-    auto sortfunc = [&mapMix, &hasher](CNode* pnode) {
+    std::array<std::pair<uint64_t, CNode*>,2> best{{{0, nullptr}, {0, nullptr}}};
+    assert(nRelayNodes <= best.size());
+
+    auto sortfunc = [&best, &hasher, nRelayNodes](CNode* pnode) {
         if (pnode->nVersion >= CADDR_TIME_VERSION) {
             uint64_t hashKey = CSipHasher(hasher).Write(pnode->id).Finalize();
-            mapMix.emplace(hashKey, pnode);
+            for (unsigned int i = 0; i < nRelayNodes; i++) {
+                 if (hashKey > best[i].first) {
+                     std::copy(best.begin() + i, best.begin() + nRelayNodes - 1, best.begin() + i + 1);
+                     best[i] = std::make_pair(hashKey, pnode);
+                     break;
+                 }
+            }
         }
     };
 
-    auto pushfunc = [&addr, &mapMix, &nRelayNodes, &insecure_rand] {
-        for (auto mi = mapMix.begin(); mi != mapMix.end() && nRelayNodes-- > 0; ++mi)
-            mi->second->PushAddress(addr, insecure_rand);
+    auto pushfunc = [&addr, &best, nRelayNodes, &insecure_rand] {
+        for (unsigned int i = 0; i < nRelayNodes && best[i].first != 0; i++) {
+            best[i].second->PushAddress(addr, insecure_rand);
+        }
     };
 
     connman.ForEachNodeThen(std::move(sortfunc), std::move(pushfunc));