Optimizing your SMP code
Most IBM processors are capable of shared-memory parallel processing. Compile with -qsmp to generate the threaded code needed to exploit this capability. The option implies a -O2 optimization level. The default behavior for the option without suboptions is to do automatic parallelization with optimization.
The most commonly used -qsmp suboptions are summarized in the following table.
Commonly used -qsmp suboptions
| Suboption | Behavior |
|---|---|
| auto | Instructs the compiler to automatically generate parallel code where possible without user assistance. This option also recognizes all the SMP directives. |
| omp | Enforces compliance with the OpenMP API for specifying explicit parallelism. |
| opt | Instructs the compiler to optimize as well as parallelize. The optimization is equivalent to -O2 –qhot in the absence of other optimization options. The default setting of -qsmp is -qsmp=auto:noomp:opt. |
| suboptions | Other values for the suboption provide control over thread scheduling, nested parallelism, locking, and so on. |
Certain thread environment variables like MALLOCMULTIHEAP, SPINLOOPTIME, or YIELDLOOPTIME may improve application performance as well. For more information, see the information in the AIX® Information Center at http://publib.boulder.ibm.com/infocenter/pseries/v5r3/index.jsp.
See the following topic for further information:
