From 1ab711f81c1b181213d1f1ec97c966b8069ba8c3 Mon Sep 17 00:00:00 2001
From: Michael Mandl <mandlm@molez.net>
Date: Wed, 20 Mar 2024 13:33:47 +0100
Subject: [PATCH] feat: reduce mutex waits in parallel finder

---
 lib_vector_search/src/parallel_finder.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/lib_vector_search/src/parallel_finder.cpp b/lib_vector_search/src/parallel_finder.cpp
index 5bfbbaa..1ea4676 100644
--- a/lib_vector_search/src/parallel_finder.cpp
+++ b/lib_vector_search/src/parallel_finder.cpp
@@ -27,13 +27,17 @@ ParallelFinder::find_prefix(string_view search_term) const {
         [](const vector<string> &word_list, const string_view &search_term,
            forward_list<const string *> &result, size_t start_index,
            size_t end_index, mutex &result_mutex) {
+          forward_list<const string *> thread_results;
           for (size_t index = start_index; index < end_index; ++index) {
             const auto &current_word = word_list[index];
             if (current_word.starts_with(search_term)) {
-              const lock_guard<mutex> lock(result_mutex);
-              result.push_front(&current_word);
+              thread_results.push_front(&current_word);
             }
           }
+          if (!thread_results.empty()) {
+            const lock_guard<mutex> lock(result_mutex);
+            result.merge(thread_results);
+          }
         },
         cref(word_list_), cref(search_term), ref(result), first_word_index,
         last_word_index, ref(result_mutex));