HP Fortran Programmer's Guide (September 2007)

Performance and optimization
Using options to control optimization
Chapter 6 149
Table 6-3 Fine-tuning optimization options
Option Level Function
+O[no]cache_pad_common +O3 or
higher
Pad [do not pad] common blocks to avoid
cache collisions. The default is
+Onocache_pad_common.
+O[no]dataprefetch +O2 or
higher
Insert [do not insert] instructions within
innermost loops to explicitly prefetch data
from memory into the data cache. The
default is +Onodataprefetch.
+O[no]entrysched All Perform [do not perform] instruction
scheduling on entry and exit code. The
default is +Onoentrysched.
+O[no]fastaccess All Enable [disable] fast access to global data.
The default is +Onofastaccess at levels 1,
2, and 3; +Ofastaccess at level 4.
+O[no]fltacc +O2 or
higher
Disable [enable] floating-point
optimizations that can result in numerical
differences. By default, the optimizer does
not perform such optimizations. For
information about the effect this option can
have on your program, refer to the HP-UX
Floating-Point Guide.
+O[no]info All Display [do not display] information about
the optimization process. This option is
most useful at level 3 and above. The
default is +Onoinfo.
+O[no]initcheck +O2 or
higher
Enable [disable] initialization of any local,
scalar, automatic variable that is found to
be uninitialized. The default is to initialize
if the variable is uninitialized with respect
to every path leading to its use. For more
information about this option, see
“Uninitialized variables” on page 238.
+O[no]inline +O3 or
higher
Enable [disable] inlining. The default is
+Oinline.