-xexplicitpar

(SPARC) Generates parallelized code based on specification of #pragma MP directives. You do the dependency analysis: analyze and specify loops for inter-iteration data dependencies. The software parallelizes the specified loops. If optimization is not at -xO3 or higher, optimization is raised to -xO3 and a warning is issued. Avoid -xexplicitpar if you do your own thread management.

The Sun Workshop includes the license required to use multiprocessor C. To get faster code, this option requires a multiprocessor system. On a single-processor system, the generated code usually runs slower.

If you identify a loop for parallelization, and the loop has dependencies, you can get incorrect results, possibly different ones with each run, and with no warnings. Do not apply an explicit parallel pragma to a reduction loop. The explicit parallelization is done, but the reduction aspect of the loop is not done, and the results can be incorrect.

In summary, to parallelize explicitly:

• Analyze the loops to find those that are safe to parallelize.

• Insert #pragma MP to parallelize a loop. See the "Explicit Parallelization and Pragmas"" for more information.

• Use the -xexplicitpar option.

An example of inserting a parallel pragma immediately before the loop is:

#pragma MP taskloop
  for (j=0; j<1000; j++){
  ...
  }

If you use -xexplicitpar and compile and link in one step, then linking automatically includes the microtasking library and the threads-safe C runtime library. If you use -xexplicitpar and compile and link in separate steps, then you must also link with -xexplicitpar.