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Tutorial 4: Round-Robin Load Balancing

This example considers a system of two parallel processor-sharing queues and studies the effect of load-balancing on the average performance of an open class of jobs. A Router node controls the routing using different strategies (random, round-robin).

Load Balancing Network Diagram 
% Example 4: Round robin load balancing
model = Network('RRLB');

source = Source(model, 'Source');
lb = Router(model, 'LB');
queue1 = Queue(model, 'Queue1', SchedStrategy.PS);
queue2 = Queue(model, 'Queue2', SchedStrategy.PS);
sink  = Sink(model, 'Sink');

oclass = OpenClass(model, 'Class1');
source.setArrival(oclass, Exp(1));
queue1.setService(oclass, Exp(2));
queue2.setService(oclass, Exp(2));

model.addLink(source, lb);
model.addLink(lb, queue1);
model.addLink(lb, queue2);
model.addLink(queue1, sink);
model.addLink(queue2, sink);

lb.setRouting(oclass, RoutingStrategy.RAND);
jmtAvgTable = JMT(model,'seed',23000).avgTable()

lb.setRouting(oclass, RoutingStrategy.RROBIN);
model.reset();
jmtAvgTableRR = JMT(model,'seed',23000).avgTable()
// Example 4: Round robin load balancing
val model = Network("RRLB")

val source = Source(model, "Source")
val lb = Router(model, "LB")
val queue1 = Queue(model, "Queue1", SchedStrategy.PS)
val queue2 = Queue(model, "Queue2", SchedStrategy.PS)
val sink = Sink(model, "Sink")

val oclass = OpenClass(model, "Class1")
source.setArrival(oclass, Exp(1.0))
queue1.setService(oclass, Exp(2.0))
queue2.setService(oclass, Exp(2.0))

model.addLink(source, lb)
model.addLink(lb, queue1)
model.addLink(lb, queue2)
model.addLink(queue1, sink)
model.addLink(queue2, sink)

lb.setRouting(oclass, RoutingStrategy.RAND)
JMT(model, "seed", 23000).avgTable.print()

lb.setRouting(oclass, RoutingStrategy.RROBIN)
model.reset()
JMT(model, "seed", 23000).avgTable.print()
from line_solver import *

model = Network('RRLB')
source = Source(model, 'Source')
lb = Router(model, 'LB')
queue1 = Queue(model, 'Queue1', SchedStrategy.PS)
queue2 = Queue(model, 'Queue2', SchedStrategy.PS)
sink = Sink(model, 'Sink')

oclass = OpenClass(model, 'Class1')
source.set_arrival(oclass, Exp(1))
queue1.set_service(oclass, Exp(2))
queue2.set_service(oclass, Exp(2))

model.add_link(source, lb)
model.add_link(lb, queue1)
model.add_link(lb, queue2)
model.add_link(queue1, sink)
model.add_link(queue2, sink)

lb.set_routing(oclass, RoutingStrategy.RAND)
jmtAvgTable = JMT(model, seed=23000).avg_table()

model.reset()
lb.set_routing(oclass, RoutingStrategy.RROBIN)
jmtAvgTableRR = JMT(model, seed=23000).avg_table()

Expected Output (Random Routing)

jmtAvgTable =
    Station    JobClass     QLen       Util       RespT     ResidT      ArvR       Tput
    _______    ________    _______    _______    _______    _______    _______    _______
    Source      Class1           0          0          0          0          0     1.0135
    Queue1      Class1     0.31612    0.24682    0.65411    0.32706    0.50144      0.501
    Queue2      Class1     0.33403    0.25076    0.68406    0.34203    0.50446    0.50413

Expected Output (Round-Robin Routing)

jmtAvgTableRR =
    Station    JobClass     QLen       Util       RespT     ResidT      ArvR       Tput
    _______    ________    _______    _______    _______    _______    _______    _______
    Source      Class1           0          0          0          0          0     1.0089
    Queue1      Class1     0.30429    0.26118    0.58482    0.29241     0.5029    0.50526
    Queue2      Class1     0.29282    0.24397    0.57293    0.28647    0.50496    0.50526
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