Information Technology Reference
In-Depth Information
Figure 2. Basic model of VC systems .
easy for programmers to write different VC applications, while allowing researchers
to study and develop the underlying mechanisms behind them.
2.3.
VC Model
To discuss the performance and reliability of VCs, the behavior of VC systems must be
modeled. Here, we provide three models, i.e., basic model for defining computational be-
havior of VCs, sabotage model and Join/Departure model for workers' behavior. While this
section does not cover all detailed behavior of real VC systems, we believe it is nevertheless
useful for comparison study.
2.3.1.
Basic Model
The basic model of VC is the well known work-pool-based master-worker model [24, 29,
23, 20]. This model is used in almost all VC systems practically. Figure 2 illustrates the
model. Details of the model are described as follows.
•
A VC system consists of a management node (master) and
W
different volunteer
nodes (workers).
•
A computation to be executed in the VC system is divided into
N
independent jobs.
•
At the start of the computation, all jobs are placed in a work pool of the master.
•
The master gives a job to each idle worker.
•
Each worker executes an allocated job and returns the result to the master. During
their execution, no communication exists among workers because jobs are mutually
independent.
