Parallel Programming Guide for HP-UX Systems

Glossary
optimization
Glossary208
optimization Code transformations made
by the compiler to improve program
performance.
overflow An exception condition that
occurs when the result of a floating-point
operation is greater than the largest
normalized number. See also integer
overflow..
parallel execution Program execution on
multiple processors at the same time. One of
the optimizations performed by the compiler
is to transform eligible program loops for
parallel execution.
parallelization An optimization that
transforms eligible program loops for
parallel execution on a multiprocessor
machine.
PIC See position-independent code.
porting In this document, porting refers to
the process of moving a program that was
coded for another vendor’s Fortran to
HP Fortran 90. See also migrating..
position-independent code Object code
that contains no absolute addresses.
Position-independent code (PIC) has linkage
tables that contain pointers to code and data.
This table is filled in by the loader at
runtime. Object code that consists of PIC can
be used to create shared libraries.
precision The number of digits to which
floating-point numbers are represented.
Double-precision numbers can have greater
precision than single-precision numbers.
profilers Programming tools that
determine where a program spends its
execution time. Profilers that come with
HP Fortran 90 include prof, gprof, and
CXperf.
R-S
roundoff error The loss of precision that
can occur as a result of floating-point
arithmetic. Different orders of evaluating a
floating-point expression can produce
different accumulations of roundoff errors,
which in turn can sometimes cause the
expression to yield significantly different
results.
row-major order The method of storing
C-language arrays in memory. (Fortran
arrays are stored in column-major order.)
Row-major order requires the rows of a
two-dimensional array to be in contiguous
memory locations. For example, given the
array a[3][4], element a[0][0] would be
stored in the first location, a[0][1] in the
second, a[0][2] in the third, and so on.
segmentation violation A type of
exception that occurs when an executing
program attempts to access memory outside
of its allocated memory segment; also called
a memory fault.
serial execution Program execution on
only one processor at a time. See also
parallel execution..
shared executable An executable program
whose text segment (that is, its code) can be
shared by multiple processes.