HP Fortran Programmer's Guide (B3908-90031; September 2011)

Compiling and linking
Compiling with the f90 command
Chapter 2 73
NOTE The +Oparallel option should not be used for programs that make
explicit calls to the kernel threads library.
+Oparallel_intrinsics
+Oparallel_intrinsics links in the parallel version of many of the Fortran
intrinsics located in libF90_parallel.
+O[no]parmsoverlap
+Oparmsoverlap causes the optimizer to assume that the actual arguments of
function calls overlap in memory, thus preventing any optimizations that violate this
assumption. This option is only effective at optimization level 2 or higher.
Use the +Onoparmsoverlap option with programs that conform to the standard
requirement that parameters must not overlap.
The default is +Onoparmsoverlap.
+O[no]pipeline
+Opipeline enables software pipelining. This option is only effective at optimization
level 2 or higher.
Use +Onopipeline (disable software pipelining) to conserve code space.
The default is +Opipeline.
NOTE This option is valid only on the PA-RISC systems.
+Oprefetch_latency=num option
Applies to loops for which the compiler generates data prefetch instructions. For a given
loop, the compiler divides “cycles” by the estimated loop length to arrive at the number
of loop iterations for which to generate advance prefetches. The default value is 480
cycles for loops containing floating-point accesses and 150 cycles for loops that do not
contain any floating-point accesses. For tuning purposes, it is recommended that users
measure their application’s performance using a few different prefetch latency settings
to determine the optimal value. Some floating-point codes may benefit by increasing the
distance to 960. Parallel applications frequently benefit from a shorter prefetch distance
of 150.
+O[no]procelim When +Oprocelim is specified, procedures that are not referenced by the application
are eliminated from the output executable file. When +Onoprocelim is specified,
procedures that are not referenced by the application are not eliminated from the output
executable file. You can use this option at any level of optimization.