HP-MPI User's Guide (11th Edition)

Glossary
non–determinism
Glossary314
Nonblocking sends are useful when
communication and computation can be
effectively overlapped in an MPI application.
non–determinism A behavior describing
non-repeatable parameters. A property of
computations which may have more than
one result. The order of a set of events
depends on run time conditions and so varies
from run to run.
OpenFabrics Alliance (OFA) A
not-for-profit organization dedicated to
expanding and accelerating the adoption of
Remote Direct Memory Access (RDMA)
technologies for server and storage
connectivity.
OpenFabrics Enterprise Distribution
(OFED) The open-source software stack
developed by OFA that provides a unified
solution for the two major RDMA fabric
technologies: InfiniBand and iWARP (also
known as RDMA over Ethernet).
parallel efficiency An increase in speed in
the execution of a parallel application.
point-to-point communication Com-
munication where data transfer involves
sending and receiving messages between two
processes. This is the simplest form of data
transfer in a message-passing model.
polling Mechanism to handle asynchronous
events by actively checking to determine if
an event has occurred.
process Address space together with a
program counter, a set of registers, and a
stack. Processes can be single threaded or
multithreaded. Single-threaded processes
can only perform one task at a time.
Multithreaded processes can perform
multiple tasks concurrently as when
overlapping computation and
communication.
race condition Situation in which multiple
processes vie for the same resource and
receive it in an unpredictable manner. Race
conditions can lead to cases where
applications do not run correctly from one
invocation to the next.
rank Integer between zero and (number of
processes - 1) that defines the order of a
process in a communicator. Determining the
rank of a process is important when solving
problems where a master process partitions
and distributes work to slave processes. The
slaves perform some computation and return
the result to the master as the solution.
ready send mode Form of blocking send
where the sending process cannot start until
a matching receive is posted. The sending
process returns immediately.
reduction Binary operations (such as
addition and multiplication) applied globally
to all processes in a communicator. These
operations are only valid on numeric data
and are always associative but may or may
not be commutative.
scalable Ability to deliver an increase in
application performance proportional to an
increase in hardware resources (normally,
adding more processors).
scatter One-to-many operation where the
root’s send buffer is partitioned into n
segments and distributed to all processes
such that the ith process receives the ith
segment. n represents the total number of
processes in the communicator.