HP Fortran Programmer's Guide (March 2010)

Performance and optimization
Using options to control optimization
Chapter 6156
+Ofast All Select a combination of optimization
options for optimum execution speed and
reasonable build times. Currently chosen
options are:
• +O2
• +Ofltacc=relaxed
• +Onolimit
• +DSnative
• +FPD
• -Wl,+pi,1M
• -Wl,+pd,1M
• -Wl,+mergeseg
NOTE:
Do not use this option for programs that
depend on IEEE standard floating point
denormalized numbers. Otherwise,
different numerical results may occur. See
+Ofltacc=relaxed. This option is a
synonym for -fast.
+Ofaster All This option is equivalent to +Ofast with an
increased optimization level. The
definition of +Ofaster may change or it
may be deprecated in future releases.
+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.
Table 6-3 Fine-tuning optimization options (Continued)
Option Level Function