HP-UX Floating-Point Guide

176 Chapter 7
Performance Tuning
Inefficient Code
use+Oaggressive +Onovectorize
if you want aggressive optimization
without vector calls.
Any files that were compiled with
+Ovectorize must also be linked
with +Ovectorize (this happens
automatically when the compiler
invokes the linker).
This option can be used at
optimization levels 3 and 4. The
default is +Onovectorize. This
option is valid only when you compile
for PA1.1 and PA2.0 systems.
If your PA2.0 application uses very
large arrays, you may gain
considerable performance benefit
from using +Odataprefetch in
conjunction with +Ovectorize. The
math library contains special
prefetching versions of the vector
routines, which are called if you
specify both options.
Specifying the Architecture Type
All HP 9000 compilers support the +DA option, which specifies a
particular target architecture type. Use of this option causes the
compiler to produce architecture-specific instructions and calls to special
architecture-specific run-time libraries. For details about +DA, see
“Selecting Different Versions of the Math Libraries” on page 27.
Specifying the architecture type of the systems on which your code will
run will probably improve the performance of your code if it makes
substantial use of floating-point arithmetic or math library calls. See
“Architecture Type of Run-Time System” on page 80 and “BLAS Library
Versions” on page 180 for more information.
If your code will run on PA2.0 systems only, you will probably get the
best performance if you use the default 32-bit code generation option
(+DA2.0) rather than 64-bit code generation (+DA2.0W). Generate 64-bit
code only if your application must do so to avoid the system constraints
of 32-bit systems.