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latency. The time interval between the instant at which
an instruction control unit initiates a call for data
transmission, and the instant at which the actual
transfer of data (or receipt of data at the remote end)
begins. Latency is related to the hardware
characteristics of the system and to the different layers
of software that are involved in initiating the task of
packing and transmitting the data.
Licensed Program Product (LPP). A collection of
software packages, sold as a product, that customers
pay for to license. It can consist of packages and
filesets a customer would install. These packages and
filesets bear a copyright and are offered under the
terms and conditions of a licensing agreement. See also
fileset
and
package
.
| LoadLeveler. A job management system that works
| with POE to allow users to run jobs and match
| processing needs with system resources, in order to
| better utilize the system.
local variable. A variable that is defined and used
only in one specified portion of a computer program.
loop unrolling. A program transformation which
makes multiple copies of the body of a loop, placing the
copies also within the body of the loop. The loop trip
count and index are adjusted appropriately so the new
loop computes the same values as the original. This
transformation makes it possible for a compiler to take
additional advantage of instruction pipelining, data
cache effects, and software pipelining.
See also
optimization
.
M
menu. A list of options displayed to the user by a data
processing system, from which the user can select an
action to be initiated.
message catalog. A file created using the AIX
Message Facility from a message source file that
contains application error and other messages, which
can later be translated into other languages without
having to recompile the application source code.
message passing. Refers to the process by which
parallel tasks explicitly exchange program data.
MIMD (Multiple Instruction Multiple Data). A parallel
programming model in which different processors
perform different instructions on different sets of data.
MPMD (Multiple Program Multiple Data). A parallel
programming model in which different, but related,
programs are run on different sets of data.
MPI. Message Passing Interface; a standardized API
for implementing the message passing model.
N
network. An interconnected group of nodes, lines, and
terminals. A network provides the ability to transmit data
to and receive data from other systems and users.
node. (1) In a network, the point where one or more
functional units interconnect transmission lines. A
computer location defined in a network. (2) In terms of
the IBM RS/6000 SP, a single location or workstation in
a network. An SP node is a physical entity (a
processor).
node ID. A string of unique characters that identifies
the node on a network.
nonblocking operation. An operation, such as
sending or receiving a message, which returns
immediately whether or not the operation was
completed. For example, a nonblocking receive will not
wait until a message is sent, but a blocking receive will
wait. A nonblocking receive will return a status value
that indicates whether or not a message was received.
O
object code. The result of translating a computer
program to a relocatable, low-level form. Object code
contains machine instructions, but symbol names (such
as array, scalar, and procedure names), are not yet
given a location in memory.
optimization. A not strictly accurate but widely used
term for program performance improvement, especially
for performance improvement done by a compiler or
other program translation software. An optimizing
compiler is one that performs extensive code
transformations in order to obtain an executable that
runs faster but gives the same answer as the original.
Such code transformations, however, can make code
debugging and performance analysis very difficult
because complex code transformations obscure the
correspondence between compiled and original source
code.
option flag. Arguments or any other additional
information that a user specifies with a program name.
Also referred to as
parameters
or
command line
options
.
Glossary of Terms and Abbreviations 191