add enable/disable functionality to timer

include/kamping/measurements/timer.hpp

@@ -128,7 +128,7 @@ class Timer {
     /// @brief Constructs a timer using a given communicator.
     ///
     /// @param comm Communicator in which the time measurements are executed.
-    Timer(CommunicatorType const& comm) : _timer_tree{}, _comm{comm} {}
+    Timer(CommunicatorType const& comm) : _timer_tree{}, _comm{comm}, _is_timer_enabled{true} {}
 
     /// @brief Synchronizes all ranks in the underlying communicator via a barrier and then start the measurement with
     /// the given key.
@@ -199,6 +199,15 @@ class Timer {
         _timer_tree.reset();
     }
 
+    /// @brief (Re-)Enable start/stop operations.
+    void enable() {
+        _is_timer_enabled = true;
+    }
+    /// @brief Disable start/stop operations, i.e., start()/stop() operations do not have any effect.
+    void disable() {
+        _is_timer_enabled = false;
+    }
+
     /// @brief Aggregates and outputs the executed measurements. The output is done via the print()
     /// method of a given Printer object.
     ///
@@ -220,11 +229,15 @@ class Timer {
 
 private:
     internal::TimerTree<double, Duration>
-                            _timer_tree; ///< Timer tree used to represent the hierarchical time measurements.
-    CommunicatorType const& _comm;       ///< Communicator in which the time measurements take place.
+                            _timer_tree;       ///< Timer tree used to represent the hierarchical time measurements.
+    CommunicatorType const& _comm;             ///< Communicator in which the time measurements take place.
+    bool                    _is_timer_enabled; ///< Flag indicating whether start/stop operations are enabled.
 
     /// @brief Starts a time measurement.
     void start_impl(std::string const& key, bool use_barrier) {
+        if (!_is_timer_enabled) {
+            return;
+        }
         auto& node = _timer_tree.current_node->find_or_insert(key);
         node.is_active(true);
         if (use_barrier) {
@@ -243,6 +256,9 @@ class Timer {
     void stop_impl(
         LocalAggregationMode local_aggregation_mode, std::vector<GlobalAggregationMode> const& global_aggregation_modes
     ) {
+        if (!_is_timer_enabled) {
+            return;
+        }
         auto endpoint = Environment<>::wtime();
         KASSERT(
             _timer_tree.current_node->is_active(),

tests/measurements/mpi_timer_test.cpp

@@ -67,7 +67,7 @@ struct VisitorReturningSizeAndCategory {
         return std::make_pair(vec.size(), false);
     }
 };
-// Traverses the evaluation tree and returns a smmary of the aggregated data that can be used to verify to some degree
+// Traverses the evaluation tree and returns a summary of the aggregated data that can be used to verify to some degree
 // the executed timings
 struct ValidationPrinter {
     void print(measurements::AggregatedTreeNode<double> const& node) {
@@ -373,3 +373,41 @@ TEST(TimerTest, singleton) {
         EXPECT_EQ(printer.output, expected_output);
     }
 }
+
+TEST(TimerTest, enable_disable) {
+    Communicator<> comm;
+    Timer<>        timer;
+    timer.disable();
+    timer.start("measurement1");
+    timer.enable();
+    {
+        timer.start("measurement11");
+        timer.stop({measurements::GlobalAggregationMode::gather, measurements::GlobalAggregationMode::max});
+        timer.start("measurement12");
+        {
+            timer.synchronize_and_start("measurement121");
+            timer.stop();
+        }
+        timer.stop();
+        timer.start("measurement11");
+        timer.stop();
+    }
+    timer.disable();
+    timer.stop_and_append();
+    timer.enable();
+    ValidationPrinter printer;
+    timer.aggregate_and_print(printer);
+    if (comm.is_root()) {
+        std::unordered_map<std::string, AggregatedDataSummary> expected_output{
+            {"root.measurement11:gather",
+             AggregatedDataSummary{}.set_is_scalar(false).set_num_entries(1).set_num_values(comm.size())},
+            {"root.measurement12:max",
+             AggregatedDataSummary{}.set_is_scalar(true).set_num_entries(1).set_num_values(1)},
+            {"root.measurement12.measurement121:max",
+             AggregatedDataSummary{}.set_is_scalar(true).set_num_entries(1).set_num_values(1)},
+            {"root.measurement11:max",
+             AggregatedDataSummary{}.set_is_scalar(true).set_num_entries(1).set_num_values(1)},
+        };
+        EXPECT_EQ(printer.output, expected_output);
+    };
+}