Parallel Programing with MPI
... standard API for portable parallel applications and
get all hardware vendors involved in
implementations of this standard; define a target
system for parallelizing compilers
End User Level Classification of Multicast Reachability Problems,
... multicast reachability problems in the network. However, it
cannot really help identify the type of the problems or their
root causes. As the multicast service is realized by using a
combination of several protocols in the Internet (PIM-SM,
MSDP, and MBGP), information collected by these monitoring
No Slide Title
• Abstraction is each process gets own
• If receive blocks (holds processor)
– may prevent another process from running
upon which it depends
... Initially packets from a source will be sent to the RP
When a host joins a group, join messages are sent hop by hop
towards the RP
The RP serves as a meeting place between sources and receivers
This works well within a site or a single administrative domain
But we don’t want one single central commo ...
Comparison of Erlang Runtime System and Java Virtual Machine
... ERTS works by executing an intermediate representation of erlang source code, also known
as BEAM code. As mentioned there’s no specification for the generated instructions, though
a few unofficial documents are available.
Quite unlike the Java programming language Erlang is a functional programmi ...
Internet Control Message Protocol
... As you have seen today and over the last two days, many problems can occur in
routing a message from sender to receiver. The TTL timer might expire; fragmented
datagrams might not arrive with all segments intact; a gateway might misroute a
datagram, and so on. Letting the sending device know of a pr ...
Experience Mining Google’s Production Console Logs
... feature creation and machine learning. Each step not
only reduces the amount of data to process, but also
transforms the free text logs into more structured and
less noisy data. We summarize the general ideas of our
log mining techniques in this section. Readers may refer
to [19, 20] for details.
Lecture 14 - The University of Texas at Dallas
... 1. Every message that is sent is delivered correctly
2. The receiver of a message knows who sent it
3. The absence of a message can be detected
▹Assumptions #1 and #2 prevent a traitor from interfering
with the communication between two other generals
▹Assumption #3 foils a traitor who tries to prev ...
Chapter 6 Synchronization Principles
... • Two or more processes access and manipulate the
same data item together
• The outcome of the execution depends on the
“speed” of the processes and the particular order in
which each process accesses the shared data item
• Results are generally incorrect
Race condition needs to be avoided.
... In the shared-memory programming model, tasks share a common address space,
which they read and write asynchronously.
Various mechanisms such as locks/semaphores may be used to control access to the
An advantage of this model from the programmer's point of view is that the notion of
... CAVE, Powerwall, & projection systems
• Vizard provides sophisticated tools for configured and
rendering to single and multi-screen projection systems
4.5 distributed mutual exclusion
... Although contention-based distributed mutual exclusion
algorithms can have attractive properties, their messaging
overhead is high. An alternative to contention-based
algorithms is to use an explicit control token, possession
of which grants access to the critical section.
... Like DSDV, we use sequence numbers to keep
track of recent routes. Every time a node sends
a new message, it uses a new sequence
number which increases monotonically.
Development of Dependable Real
... Most of these solutions are based on the time-triggered paradigm . The time-triggered approach guarantees the important aspect of determinism of the system execution since
all points in time when system components are interacting
are known in advance.
One important representative for the time-tri ...
... • IP fails to deliver datagrams when:
– the destination machine is temporarily or permanently
disconnected from the network
– the TTL reaches zero
– intermediate routers are so congested that they can’t
process incoming data
... “main” in the old single-threaded style)
Its own registers and PC
Detecting the presence of virtual machines - index
... The value of the LDT, like the IDT and Global Descriptor Table (GDT) are readable by
unprivileged memory. The problem for the VM arises when these memory addresses are
used.  Since the VM is running under an unprivileged process itself, it cannot load or
unload the values of the registers.
GLASS - LSI
... no knowledge of computer programming from
The interface runs on Java, which has the
advantage of easy portability to any platform
The routine for treatment of events on the main
application is also generated automatically
Virtual synchrony is an interprocess message passing (sometimes called ordered, reliable multicast) technology. Virtual synchrony systems allow programs running in a network to organize themselves into process groups, and to send messages to groups (as opposed to sending them to specific processes). Each message is delivered to all the group members, in the identical order, and this is true even when two messages are transmitted simultaneously by different senders. Application design and implementation is greatly simplified by this property: every group member sees the same events (group membership changes and incoming messages) in the same order.A virtually synchronous service is typically implemented using a style of programming called state machine replication, in which a service is first implemented using a single program that receives inputs from clients through some form of remote message passing infrastructure, then enters a new state and responds in a deterministic manner. The initial implementation is then transformed so that multiple instances of the program can be launched on different machines, using a virtually synchronous message passing system to replicate the incoming messages over the members. The replicas will see the same events in the same order, and are in the same states, hence they will make the same state transitions and remain in a consistent state.The replication of the service provides a form of fault-tolerance: if a replica fails (by crashing), the others remain and can continue to provide responses. Different members of the replica group can also be programmed to subdivide the workload, typically by using the group membership to determine their respective roles. This permits a group of N members to run as much as N times faster than a single member, or to handle N times as many requests, while continuing to offer fault-tolerance in the event of a crash.Virtual synchrony is distinguished from classical state machine replication because the model includes features whereby a programmer can request early (optimistic) delivery of messages, or relaxed forms of ordering. When used appropriately, these features can enable substantial speedup. However, the programmer needs to be sure that the relaxation of guarantees will not compromise correctness.For example, in a service that uses locking to protect concurrently updated data, the messaging system can be instructed to use an inexpensive form of message ordering, in which the messaging system respects the ordering in which individual senders send messages (FIFO guarantee) but does not attempt to impose an agreed order if messages are sent concurrently by different senders. Provided that the sender indeed held locks on the data, it can be shown that FIFO ordering suffices for correctness. The benefit is that FIFO ordering is much less costly to implement than total ordering for concurrent messages.To give another example, by delivering messages optimistically, virtual synchrony systems can outperform the Paxos that is normally required for implementation of state machine replication: Paxos normally requires a 2-phase protocol, whereas optimistic virtual synchrony protocols can deliver messages immediately upon their arrival. However, this could result in a violation of the safety property of the state machine replication model. To prevent such problems, the programmer who uses this feature is required to invoke a primitive called flush, which delays the caller until any optimistically delivered messages have reached all of the group members. Provided that the programmer understands this behavior and is careful to call flush before interacting with external clients or persistent storage, higher performance can be achieved without loss of safety.The flexibility associated with these limited forms of event reordering and optimistic early delivery permit virtual synchrony platforms to achieve extremely high data rates while still preserving very strong fault-tolerance and consistency guarantees.