Use the DEFAULT clause on the PARALLEL, PARALLEL DO, and PARALLEL SECTIONS directives to specify a default data scope attribute for all variables within the lexical extent of a parallel region. Variables in THREADPRIVATE common blocks are not affected by this clause. You can specify only one DEFAULT clause on a directive. The default data scope attribute can be one of the following:
Attribute |
Description |
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PRIVATE |
Makes all named objects in the lexical extent of the parallel region private to a thread. The objects include common block variables, but exclude THREADPRIVATE variables. |
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SHARED |
Makes all named objects in the lexical extent of the parallel region shared among all the threads in the team. |
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NONE |
Declares that there is no implicit default as to whether variables are PRIVATE or SHARED. You must explicitly specify the scope attribute for each variable in the lexical extent of the parallel region. |
If you do not specify the DEFAULT clause, the default is DEFAULT (SHARED). However, loop control variables are always PRIVATE by default.
You can exempt variables from the default data scope attribute by using other scope attribute clauses on the parallel region as shown in the following example:
Example |
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!$OMP PARALLEL DO DEFAULT(PRIVATE), FIRSTPRIVATE(I),SHARED(X), |