Merge pull request #128 from CiwPython/server_overtime

Server overtime

Author: geraintpalmer

ciw/node.py

@@ -48,6 +48,7 @@ def __init__(self, id_, simulation):
             self.simulation.network.number_of_classes)]
         if self.schedule:
             self.next_event_date = self.next_shift_change
+            self.overtime = []
         else:
             self.next_event_date = float("Inf")
         self.blocked_queue = []
@@ -330,6 +331,8 @@ def kill_server(self, srvr):
         Kills server.
         """
         srvr.total_time = self.increment_time(self.next_event_date, -srvr.start_date)
+        self.overtime.append(
+            self.increment_time(self.next_event_date, -srvr.shift_end))
         self.all_servers_busy.append(srvr.busy_time)
         self.all_servers_total.append(srvr.total_time)
         indx = self.servers.index(srvr)
@@ -394,13 +397,15 @@ def take_servers_off_duty(self):
         if not self.preempt:
             to_delete = []
             for srvr in self.servers:
+                srvr.shift_end = self.next_event_date
                 if srvr.busy:
                     srvr.offduty = True
                 else:
                     to_delete.append(srvr)
         else:
             to_delete = self.servers[::1]  # copy
             for s in self.servers:
+                s.shift_end = self.next_event_date
                 if s.cust is not False:
                     self.interrupted_individuals.append(s.cust)
                     self.interrupted_individuals[-1].service_end_date = False

ciw/server.py

@@ -17,6 +17,7 @@ def __init__(self, node, id_number, start_date=0.0):
         self.start_date = start_date
         self.busy_time = False
         self.total_time = False
+        self.shift_end = False
 
     @property
     def utilisation(self):

ciw/tests/test_scheduling.py

@@ -1,5 +1,7 @@
 import unittest
 import ciw
+from decimal import Decimal
+
 
 class TestScheduling(unittest.TestCase):
 
@@ -251,3 +253,30 @@ def test_full_preemptive_simulation(self):
         # finishing at time 12.5 (total: 9.5 time units). Then server goes off duty
         # for 4.5 time units (total: 14 time units). Then resample service time and
         # get serviced for another 10 time units (total: 24 time units).
+
+
+    def test_overtime(self):
+        N = ciw.create_network(
+            Arrival_distributions=[['Sequential', [1.0, 0.0, 0.0, 8.0, 0.0, 3.0, 10000.0]]],
+            Service_distributions=[['Sequential', [5.0, 7.0, 9.0, 4.0, 5.0, 5.0]]],
+            Number_of_servers=[([[3, 7.0], [2, 11.0], [1, 20.0]], False)]
+        )
+        Q = ciw.Simulation(N)
+        Q.simulate_until_max_time(19.0)
+
+        nd = Q.transitive_nodes[0]
+        self.assertEqual(nd.overtime, [0.0, 1.0, 3.0, 2.0, 3.0])
+        self.assertEqual(sum(nd.overtime)/len(nd.overtime), 1.8)
+
+    def test_overtime_exact(self):
+        N = ciw.create_network(
+            Arrival_distributions=[['Sequential', [1.0, 0.0, 0.0, 8.0, 0.0, 3.0, 10000.0]]],
+            Service_distributions=[['Sequential', [5.0, 7.0, 9.0, 4.0, 5.0, 5.0]]],
+            Number_of_servers=[([[3, 7.0], [2, 11.0], [1, 20.0]], False)]
+        )
+        Q = ciw.Simulation(N, exact=26)
+        Q.simulate_until_max_time(19.0)
+
+        nd = Q.transitive_nodes[0]
+        self.assertEqual(nd.overtime, [Decimal('0.0'), Decimal('1.0'), Decimal('3.0'), Decimal('2.0'), Decimal('3.0')])
+        self.assertEqual(sum(nd.overtime)/len(nd.overtime), Decimal('1.8'))

docs/Guides/server_schedule.rst

@@ -68,3 +68,25 @@ Ciw defaults to non-pre-emptive schedules, and so the following code implies a n
 
     Number_of_servers=[[[2, 10], [0, 30], [1, 100]]] # non-preemptive
 
+
+
+Overtime
+--------
+
+Non-preemptive schedules allow for the possibility of overtime, that is servers working after their shift has ended in order to complete a customer's service.
+The amount of overtime each server works is recorded in the Node object's :code:`overtime` attribute.
+Consider the following example::
+
+    >>> import ciw
+    >>> N = ciw.create_network(
+    ...     Arrival_distributions=[['Deterministic', 3.0]],
+    ...     Service_distributions=[['Deterministic', 5.0]],
+    ...     Number_of_servers=[[[1, 4.0], [2, 10.0], [0, 100.0]]]
+    ... )
+    >>> Q = ciw.Simulation(N)
+    >>> Q.simulate_until_max_time(20.0)
+
+    >>> Q.transitive_nodes[0].overtime
+    [4.0, 1.0, 4.0]
+
+Here we see that the first server that went off duty worked 4.0 time units of overtime, the second worked 1.0 time unit of overtime, and the third worked 4.0 time units of overtime.