Technical data

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Chapter 6: Compiling and Debugging Parallel Fortran

Using the –static Flag

A few words of caution about the –static ﬂag: The multiprocessing

implementation demands some use of the stack to allow multiple threads of

execution to execute the same code simultaneously. Therefore, the parallel

DO loops themselves are compiled with the –automatic ﬂag, even if the

routine enclosing them is compiled with –static.

This means that SHARE variables in a parallel loop behave correctly

according to the –static semantics but that LOCAL variables in a parallel

loop will not (see “Debugging Parallel Fortran” on page 110 for a description

of SHARE and LOCAL variables).

Finally, if the parallel loop calls an external routine, that external routine

cannot be compiled with –static. You can mix static and multiprocessed

object ﬁles in the same executable; the restriction is that a static routine

cannot be called from within a parallel loop.

Examples of Compiling

This section steps you through a few examples of compiling code using –mp.

The following command line

% f77 –mp foo.f

compiles and links the Fortran program foo.f into a multiprocessor

executable.

In this example

% f77 –c –mp –O2 snark.f

the Fortran routines in the ﬁle snark.f are compiled with multiprocess code

generation enabled. The optimizer is also used. A standard snark.o binary is

produced, which must be linked:

% f77 –mp –o boojum snark.o bellman.o

Here, the –mp ﬂag signals the linker to use the Fortran multiprocessing

library. The ﬁle bellman.o need not have been compiled with the –mp ﬂag

(although it could have been).