ns2 project in Quebec
ns2 project in Quebeca data or control
dependency exists between the successive tasks, which imposes ns2 project in Quebec a precedence requirement on their scheduling. The sequences of tasks may span multiple processors and one simple task can belong to more than one end-to-end task. Tasks are the units of scheduling in the computational model,ns2 project in Quebec but they are not the only components of the model.
In fact, because we consider the possibility of a certain level of complexity in the tasks, we also consider the blocks of code executed within the tasks in the computational model. In the ns2 project in Quebec simplest case, only one block of code corresponds to the whole code of one task. The existence of computational units ns2 project in Quebec within the task in our model will also permit the construction of a more detailed behavioural
model to support the analysis of end-to-end tasks, as will be shown below.
The analysis of the behaviour ns2 project in Quebec of the end-to-end transactions
is supported by a behavioural model that clearly explains
the way the sequences of activities take place.
To describe the temporal ns2 project in Quebec behaviour of PDES in terms
of events, delays and actions, several approaches or be- havioural models can be employed: models based on eventordering graphs such as execution graphs [18] and Petri
Nets [11]; structured models based on state machines such
as the control flow of Hatley and Pirbai [5]; and models
based on process ns2 project in Quebec algebras such as CSP [6]. A model based
on an event-ordering graph has been selected as the behavioural
model for this research work. The selection was
made as a result of its simplicity and wide applicability.
The model is composed of two main elements [23]: 1)
Activities, which are represented by ns2 project in Quebec a sequence of three
events: Ready, when the activity is ready to start; Begin,
when it starts; and End, when it finishes; and 2) A set
of precedence and synchronization relationships defined on
the ready and end events, which ns2 project in Quebec establish partial ordering
for a group of activities. These relationships give rise to
the kinds of activities represented in Figure 1. SEQuence
implies chains of communicating activities in a transaction.
SYNchronization implies activities ns2 project in Quebec that also communicate
with activities belonging to other transactions. ALTernation
implies a group of alternative activities in a transaction (supported
by blocks in the same or different tasks) where only
one activity has place on each instance of the transaction.
REPlication implies the same ns2 project in Quebec order as ALTernation, but in
this case the activities are replicas (activities with the same
function and code) useful to increase the throughput of the
transaction. Finally, PARallel implies activities in a transaction, developed in
parallel in different processors.