HP Fortran Programmer's Guide (March 2010)

Compiling and linking
Compiling with the f90 command
Chapter 2 65
On HP 9000 systems, when +Oautopar is used with the +Oparallel option,
+O4 is inhibited. If automatic parallelization is desired along with +O4,
then use +Oautopar and omit +Oparallel.
To compile a program with +Oautopar support, the libcps, libomp , and
libpthreads runtime support libraries must be present at compile-time
and runtime. This feature is available on Itanium-based systems and HP
9000 systems.
+O[no]conservative
+Oconservative causes the optimizer to make conservative assumptions
about the code when optimizing it. This option is only effective at
optimization level 2 or higher.
The +Oconservative option sets the following options:
• +Ofltacc
• +Onofltacc
• +Onomoveflops
• +Oparmsoverlap
Use +Oconservative when conservative assumptions are necessary due to
the coding style, as with nonstandard-conforming programs. Note that it is
incompatible with +Oaggressive.
The +Onoconservative option relaxes the optimizer’s assumptions about
the target program.
The default is +Onoconservative. This option has been deprecated starting
with HP-UX version 11i and later.
+O[no]limit
+Olimit suppresses optimizations that significantly increase compilation
time or that can consume large amounts of memory at compile time. This
option is only effective at optimization level 2 or higher.
The +Onolimit option allows optimizations to be performed regardless of
their effect on compilation time or memory usage.
The default is +Olimit.
+O[no]loop_transform
Enables [disables] the following transformations: loop unroll and jam, loop
distribution, loop interchange, loop blocking, loop fusion, and loop unroll.