Enable explicit parallelization with OpenMP directives.
The flag accepts the following suboption keywords:
Enables recognition of OpenMP pragmas. The optimization level under -xopenmp=parallel is -xO3. The compiler raises the optimization level to -xO3 if necessary and issues a warning.
This flag also defines the preprocessor macro _OPENMP. The _OPENMP macro is defined to have the decimal value yyyymm where yyyy and mm are the year and month designations of the version of the OpenMP API that the implementation supports. Refer to the Oracle Solaris Studio OpenMP API User's Guide for the value of the _OPENMP macro for a particular release.
Enables recognition of OpenMP pragmas. The compiler does not raise the optimization level if it is lower than -xO3. If you explicitly set the optimization lower than -xO3, as in f95 -xO2 -xopenmp=noopt, the compiler issues an error. If you do not specify an optimization level with -xopenmp=noopt, the OpenMP pragmas are recognized, the program is parallelized accordingly, but no optimization is done. This suboption also defines the preprocessor macro _OPENMP.
Does not enable the recognition of OpenMP pragmas, makes no change to the optimization level of your program, and does not define any preprocessor macros. This is the default when -xopenmp is not specified.
If you specify -xopenmp, but do not specify a suboption keyword, the compiler assumes -xopenmp=parallel. If you do not specify -xopenmp at all, the compiler assumes -xopenmp=none.
Suboptions parallel and noopt will invoke -stackvar automatically.
If you are debugging an OpenMP program with dbx, compile with -g -xopenmp=noopt so you can breakpoint within parallel regions and display the contents of variables.
The default for -xopenmp might change in a future release. You can avoid warning messages by explicitly specifying an appropriate optimization level.
Use the OMP_NUM_THREADS environment variable to specify the number of threads to use when running an OpenMP program. If OMP_NUM_THREADS is not set, the default number of threads used to execute a parallel region is the number of cores available on the machine, capped at 32. You can specify a different number of threads by setting the OMP_NUM_THREADS environment variable, or by calling the omp_set_num_threads() OpenMP runtime routine, or by using the num_threads clause on the parallel region directive. For best performance, the number of threads used to execute a parallel region should not exceed the number of hardware threads (or virtual processors) available on the machine. On Oracle Solaris systems, this number can be determined by using the psrinfo(1M) command. On Linux systems, this number can be determined by inspecting the file /proc/cpuinfo. See the OpenMP API User's Guide for more information.
Nested parallelism is disabled by default. To enable nested parallelism, you must set the OMP_NESTED environment variable to TRUE. See the OpenMP API User’s Guide.
If you compile and link in separate steps, specify -xopenmp in both the compilation step and the link step. When used with the link step, the -xopenmp option will link with the OpenMP runtime support library, libmtsk.so.
For up-to-date functionality and performance, make sure that the latest patch of the OpenMP runtime library, libmtsk.so, is installed on the system.
For more information about the OpenMP Fortran 95, C, and C++ application program interface (API) for building multithreaded applications, see the Oracle Solaris Studio OpenMP API User's Guide.