From ca63b53ecdf377ce777fd959d400748912266748 Mon Sep 17 00:00:00 2001
From: Jon Atack <jon@atack.com>
Date: Sun, 28 Feb 2021 15:53:07 +0100
Subject: [PATCH] Use std::unordered_set instead of std::vector in IsEvicted()

An unordered set can tell if an element is present in ~O(1) time (constant on
average, worst case linear to the size of the container), which speeds up and
simplifies the lookup in IsEvicted().

Co-authored-by: Vasil Dimov <vd@FreeBSD.org>
---
 src/test/net_peer_eviction_tests.cpp | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/test/net_peer_eviction_tests.cpp b/src/test/net_peer_eviction_tests.cpp
index b80beeac5a..290a6b7eae 100644
--- a/src/test/net_peer_eviction_tests.cpp
+++ b/src/test/net_peer_eviction_tests.cpp
@@ -10,6 +10,7 @@
 #include <algorithm>
 #include <functional>
 #include <optional>
+#include <unordered_set>
 #include <vector>
 
 BOOST_FIXTURE_TEST_SUITE(net_peer_eviction_tests, BasicTestingSetup)
@@ -36,20 +37,20 @@ std::vector<NodeEvictionCandidate> GetRandomNodeEvictionCandidates(const int n_c
 }
 
 // Returns true if any of the node ids in node_ids are selected for eviction.
-bool IsEvicted(std::vector<NodeEvictionCandidate> candidates, const std::vector<NodeId>& node_ids, FastRandomContext& random_context)
+bool IsEvicted(std::vector<NodeEvictionCandidate> candidates, const std::unordered_set<NodeId>& node_ids, FastRandomContext& random_context)
 {
     Shuffle(candidates.begin(), candidates.end(), random_context);
     const std::optional<NodeId> evicted_node_id = SelectNodeToEvict(std::move(candidates));
     if (!evicted_node_id) {
         return false;
     }
-    return std::find(node_ids.begin(), node_ids.end(), *evicted_node_id) != node_ids.end();
+    return node_ids.count(*evicted_node_id);
 }
 
 // Create number_of_nodes random nodes, apply setup function candidate_setup_fn,
 // apply eviction logic and then return true if any of the node ids in node_ids
 // are selected for eviction.
-bool IsEvicted(const int number_of_nodes, std::function<void(NodeEvictionCandidate&)> candidate_setup_fn, const std::vector<NodeId>& node_ids, FastRandomContext& random_context)
+bool IsEvicted(const int number_of_nodes, std::function<void(NodeEvictionCandidate&)> candidate_setup_fn, const std::unordered_set<NodeId>& node_ids, FastRandomContext& random_context)
 {
     std::vector<NodeEvictionCandidate> candidates = GetRandomNodeEvictionCandidates(number_of_nodes, random_context);
     for (NodeEvictionCandidate& candidate : candidates) {