1496 smm model output is misaligned with time points (#1497)

kilianvolmer · web-flow · commit 02bfed0644c9 · 2026-02-25T17:04:38.000+01:00
SMM advance function now works on future status vector instead of past status vector.
diff --git a/cpp/models/smm/simulation.h b/cpp/models/smm/simulation.h
@@ -83,19 +83,20 @@ class Simulation
         update_current_rates_and_waiting_times();
         size_t next_event = determine_next_event(); // index of the next event
         FP current_time   = m_result.get_last_time();
-        // set in the past to add a new time point immediately
-        FP last_result_time = current_time - m_dt;
+        // set current time to add next time point in the future
+        FP last_result_time = current_time;
         // iterate over time
         while (current_time + m_waiting_times[next_event] < tmax) {
-            // update time
-            current_time += m_waiting_times[next_event];
-            // regularily save current state in m_results
-            if (current_time > last_result_time + m_dt) {
-                last_result_time = current_time;
-                m_result.add_time_point(current_time);
+            // If the next event happens further in the future than the next stored time point, add a new one.
+            if (current_time + m_waiting_times[next_event] >= last_result_time) {
+                auto num_dt      = std::ceil((current_time + m_waiting_times[next_event] - last_result_time) / m_dt);
+                last_result_time = std::min(tmax, last_result_time + num_dt * m_dt);
+                m_result.add_time_point(last_result_time);
                 // copy from the previous last value
                 m_result.get_last_value() = m_result[m_result.get_num_time_points() - 2];
             }
+            // update time
+            current_time += m_waiting_times[next_event];
             // decide event type by index and perform it
             if (next_event < adoption_rates().size()) {
                 // perform adoption event
