XL Fortran Enterprise Edition for AIX : User's Guide - IBM

Typically, parthreshold is set to be equal to the
parallelization overhead. If the computation in
a parallelized loop is very small and the time
taken to execute these loops is spent primarily
in the setting up of parallelization, these loops
should be executed sequentially for better
performance.
seqthreshold=num
profilefreq=num
Specifies the time, in milliseconds, beyond
which a loop that was previously serialized by
the dynamic profiler should revert to being a
parallel loop. The default setting is 5
milliseconds, meaning that if a loop requires
more than 5 milliseconds to execute serially, it
should be parallelized.
seqthreshold acts as the reverse of
parthreshold.
Specifies the frequency with which a loop
should be revisited by the dynamic profiler to
determine its appropriateness for parallel or
serial execution. Loops in a program can be
data dependent. The loop that was chosen to
execute serially with a pass of dynamic
profiling may benefit from parallelization in
subsequent executions of the loop, due to
different data input. Therefore, you need to
examine these loops periodically to reevaluate
the decision to serialize a parallel loop at run
time.
The allowed values for this option are the
numbers from 0 to 32. If you set profilefreq to
one of these values, the following results will
occur.
v
v
v
If profilefreq is 0, all profiling is turned off,
regardless of other settings. The overheads
that occur because of profiling will not be
present.
If profilefreq is 1, loops parallelized
automatically by the compiler will be
monitored every time they are executed.
If profilefreq is 2, loops parallelized
automatically by the compiler will be
monitored every other time they are
executed.
v If profilefreq is greater than or equal to 2
but less than or equal to 32, each loop will
be monitored once every nth time it is
executed.
v
If profilefreq is greater than 32, then 32 is
assumed.
It is important to note that dynamic profiling is
not applicable to user-specified parallel loops
Editing, Compiling, Linking, and Running XL Fortran Programs 63