Specifies a scheduling algorithm for DO loop iterations.
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IA-32 architecture, Intel® 64 architecture, IA-64 architecture
| Linux and Mac OS: | -par-schedule-keyword[=n] |
| Windows: | /Qpar-schedule-keyword[[:]n] |
| keyword | Specifies the scheduling algorithm. Possible values are: | |
| static | Divides iterations into contiguous pieces. | |
| dynamic | Gets a set of iterations dynamically. | |
| guided | Specifies a minimum number of iterations. | |
| runtime | Defers the scheduling decision until run time. | |
| n | Is the size of the chunk or the number of iterations for each chunk. For more information, see the descriptions of each keyword below. | |
| OFF | The compiler uses default algorithms for performance tuning. |
This option specifies a scheduling algorithm for DO loop iterations. It specifies how iterations are to be divided among the threads of the team.
This option affects performance tuning and can provide better performance during auto-parallelization.
| Option | Description |
|---|---|
| -par-schedule-static or /Qpar-schedule-static | Divides iterations into contiguous pieces (chunks) of size n. The chunks are statically assigned
to threads in the team in a round-robin fashion in the order of the thread
number. Note that the last chunk to be assigned may have a smaller number
of iterations. If no n is specified, the iteration space is divided into chunks that are approximately equal in size, and each thread is assigned at most one chunk. |
| -par-schedule-dynamic or /Qpar-schedule-dynamic | Can be used to get a set of iterations dynamically. Assigns iterations
to threads in chunks as the threads request them. The thread executes
the chunk of iterations, then requests another chunk, until no chunks
remain to be assigned. As each thread finishes a piece of the iteration space, it dynamically gets the next set of iterations. Each chunk contains n iterations, except for the last chunk to be assigned, which may have fewer iterations. If no n is specified, the default is 1. |
| -par-schedule-guided or /Qpar-schedule-guided | Can be used to specify a minimum number of iterations. Assigns iterations
to threads in chunks as the threads request them. The thread executes
the chunk of iterations, then requests another chunk, until no chunks
remain to be assigned. For a chunk of size 1, the size of each chunk is proportional to the number of unassigned iterations divided by the number of threads, decreasing to 1. For an n with value k (greater than 1), the size of each chunk is determined in the same way with the restriction that the chunks do not contain fewer than k iterations (except for the last chunk to be assigned, which may have fewer than k iterations). If no n is specified, the default is 1. |
| -par-schedule-runtime or /Qpar-schedule-runtime | Defers the scheduling decision until run time. The scheduling algorithm and chunk size are then taken from the setting of environment variable OMP_SCHEDULE. You cannot specify n with this keyword. |
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