Require linking to thread–safe libraries.
Use -mt if you mix Fortran with multithreaded C code that calls the libthread library. See also the Solaris Multithreaded Programming Guide.
–mt is implied automatically when compiling with the -autopar option.
Note the following:
A function subprogram that does I/O should not itself be referenced as part of an I/O statement. Such recursive I/O may cause the program to deadlock with -mt.
In general, do not compile your own multithreaded code with -autopar. The compiler-generated calls to the threads library and the program’s own calls may conflict, causing unexpected results.
On a single–processor system, performance may be degraded with the -mt option.