close #21

src/resource.cpp

@@ -2,10 +2,16 @@
 #include "simulator.h"
 
 void Resource::set_capacity(int value) {
+  int last = capacity;
   capacity = value;
-  // serve another
-  while (queue_count) 
-    if (!try_serve_from_queue(sim->verbose, sim->now())) break;
+  if (capacity > last) {
+    // serve another
+    while (queue_count) 
+      if (!try_serve_from_queue(sim->verbose, sim->now())) break;
+  } else if (capacity < last) {
+    while (server_count > capacity) 
+      if (!try_free_server(sim->verbose, sim->now())) break;
+  }
   if (is_monitored()) observe(sim->now());
 }
 

src/resource.h

@@ -134,6 +134,8 @@ class Resource: public Entity {
     return server_count + amount <= capacity;
   }
 
+  virtual bool try_free_server(bool verbose, double time) { return false; }
+
   virtual void insert_in_server(bool verbose, double time, Arrival* arrival, int amount, 
                                 int priority, int preemptible, bool restart) {
     if (verbose) verbose_print(time, arrival->name, "SERVE");
@@ -226,21 +228,25 @@ class PreemptiveResource: public Resource {
     return false;
   }
 
+  virtual bool try_free_server(bool verbose, double time) {
+    typename T::iterator first = server.begin();
+    first->arrival->deactivate(first->restart);
+    if (verbose) verbose_print(time, first->arrival->name, "PREEMPT");
+    if (first->arrival->is_monitored()) {
+      double last = first->arrival->get_activity(this->name);
+      first->arrival->set_activity(this->name, time - last);
+    }
+    preempted.insert((*first));
+    queue_count += first->amount;
+    server_count -= first->amount;
+    server.erase(first);
+    return true;
+  }
+
   virtual void insert_in_server(bool verbose, double time, Arrival* arrival, int amount, 
                                 int priority, int preemptible, bool restart) {
-    if (capacity > 0) while (server_count + amount > capacity) {
-      typename T::iterator first = server.begin();
-      first->arrival->deactivate(first->restart);
-      if (verbose) verbose_print(time, first->arrival->name, "PREEMPT");
-      if (first->arrival->is_monitored()) {
-        double last = first->arrival->get_activity(this->name);
-        first->arrival->set_activity(this->name, time - last);
-      }
-      preempted.insert((*first));
-      queue_count += first->amount;
-      server_count -= first->amount;
-      server.erase(first);
-    }
+    if (capacity > 0) while (server_count + amount > capacity)
+      try_free_server(verbose, time);
     if (verbose) verbose_print(time, arrival->name, "SERVE");
     server_count += amount;
     server.emplace(time, arrival, amount, priority, preemptible, restart);

tests/testthat/test-simmer-resource-schedule.R

@@ -68,7 +68,7 @@ test_that("arrivals 1) are dequeued when resource's capacity increases and 2) re
 
   inf_sch <- schedule(c(0, 1, 2), c(1, 3, 1), Inf)
 
-  arrivals <- simmer(verbose=T) %>%
+  arrivals <- simmer() %>%
     add_resource("dummy", inf_sch) %>%
     add_generator("asdf", t, at(0, 0, 0)) %>%
     run() %>%
@@ -86,7 +86,7 @@ test_that("arrivals are preempted when resource's capacity decreases", {
 
   inf_sch <- schedule(c(0, 1, 2), c(1, 3, 1), Inf)
 
-  arrivals <- simmer(verbose=T) %>%
+  arrivals <- simmer() %>%
     add_resource("dummy", inf_sch, preemptive=TRUE) %>%
     add_generator("asdf", t, at(0, 0, 0)) %>%
     run() %>%