memory_orders on load operations

:Release Notes:
removed jthread, either way explicit join
additional bench test (separate mutex and unordered map)

:Detailed Notes:
-

:Testing Performed:
just tests/bench run - output is correct, no data races detected
(-fsanitize=thread)

:QA Notes:
-

:Issues Addressed:
-

.vscode/settings.json

@@ -0,0 +1,4 @@
+{
+    "editor.defaultFormatter": "xaver.clang-format",
+    "editor.formatOnSave": true
+}

bench/main.cc

@@ -94,23 +94,35 @@ static void BM_taylor_atomic_upd(benchmark::State& state) {
   }
 }
 
-void updValue(double res, const std::string& key) {
+void updMapValue(double res, const std::string& key) {
   static std::unordered_map<std::string, double> d = {{"key", 10.0},
                                                       {"assembly", 11.0},
                                                       {"draw", 123.3},
                                                       {"d2", 0.0},
                                                       {"d55", 0.23}};
+  d[key] = res;
+}
+
+static void BM_taylor_map_upd(benchmark::State& state) {
+  for (auto _ : state) {
+    double res = calc_exp_taylor();
+    updMapValue(res, "assembly");
+  }
+}
+
+void updValue(double res) {
+  static double d;
   static std::mutex mtx;
   {
     std::lock_guard lock(mtx);
-    d[key] = res;
+    d = res;
   }
 }
 
 static void BM_taylor_mutex_upd(benchmark::State& state) {
   for (auto _ : state) {
     double res = calc_exp_taylor();
-    updValue(res, "assembly");
+    updValue(res);
   }
 }
 
@@ -119,6 +131,7 @@ BENCHMARK(BM_taylor_logger);
 BENCHMARK(BM_taylor_glog);
 BENCHMARK(BM_taylor_atomic_upd);
 BENCHMARK(BM_taylor_mutex_upd);
+BENCHMARK(BM_taylor_map_upd);
 
 std::string caesar_encoder(const std::string& input) {
   static constexpr int small = 'a';

include/logger.hh

@@ -22,10 +22,13 @@ class Logger {
 
  public:
   virtual ~Logger();
+
+  Logger();
   explicit Logger(std::ostream& out);
-  Logger() = delete;
   Logger(Logger&) = delete;
   Logger(Logger&&) = delete;
+  Logger& operator=(Logger&) = delete;
+  Logger& operator=(Logger&&) = delete;
 
   /// @return success or not (already configured)
   bool configure(const std::vector<std::string>& d);
@@ -33,11 +36,11 @@ class Logger {
   template <typename Metric,
             typename = std::enable_if_t<std::is_arithmetic_v<Metric>>>
   void add(const std::string& field, Metric metric) {
-    auto locked = active.load();
+    auto locked = active.load(std::memory_order_acquire);
     // auto locked = active;
     auto it = locked->find(field);
     if (it == locked->end()) {
-      throw configErrorMsg;
+      throw configErrorMsg;  // additional 30ns on bench ?
     }
     it->second = metric;
   }
@@ -51,7 +54,8 @@ class Logger {
   std::unique_ptr<Worker> worker;
   std::shared_ptr<map_type> m1, m2;
   std::atomic<std::shared_ptr<map_type>> active;  // impl may use mutex!
-  // std::shared_ptr<map_type> active;
+  // std::shared_ptr<map_type> active;  // data race without atomic on swap
+  // operation
 };
 
 }  // namespace vptyp

src/logger.cc

@@ -1,4 +1,6 @@
 #include "logger.hh"
+#include <atomic>
+#include <memory>
 #include <thread>
 namespace vptyp {
 
@@ -18,6 +20,11 @@ bool Logger::configure(const std::vector<std::string>& d) {
   return true;
 }
 
+Logger::Logger()
+    : m1(std::make_shared<map_type>()), m2(std::make_shared<map_type>()) {
+  worker = std::make_unique<Logger::Worker>(*this, std::cout);
+}
+
 Logger::Logger(std::ostream& out)
     : m1(std::make_shared<map_type>()), m2(std::make_shared<map_type>()) {
   worker = std::make_unique<Logger::Worker>(*this, out);
@@ -31,7 +38,7 @@ class Logger::Worker {
  public:
   explicit Worker(Logger& father, std::ostream& out)
       : parent(father), out(out) {
-    thread = std::jthread([this] { routine(); });
+    thread = std::thread([this] { routine(); });
   }
 
   ~Worker() {
@@ -54,14 +61,14 @@ class Logger::Worker {
   std::atomic<State> state;
   Logger& parent;
   std::ostream& out;
-  std::jthread thread;
+  std::thread thread;  // jthread not needed, as we anyway must wait for join
 };
 
 void Logger::Worker::unroll() {
   if (!parent.isConfigured())
     return;
 
-  auto tmp = parent.active.load();
+  auto tmp = parent.active.load(std::memory_order_acquire);
   // auto tmp = parent.active;
   auto toBeActive = tmp == parent.m1 ? parent.m2 : parent.m1;
   while (!parent.active.compare_exchange_weak(tmp, toBeActive)) {