Variables Referenced in a Construct

| OPENMP API Specification: "Version 5.2 -- GIT rev 95b2e3a44"

5.1.1 Variables Referenced in a Construct

The data-sharing attributes of variables that are referenced in a construct can be predetermined, explicitly determined, or implicitly determined, according to the rules outlined in this section.

Specifying a variable in a copyprivate clause or a data-sharing attribute clause other than the private clause on an enclosed construct causes an implicit reference to the variable in the enclosing construct. Specifying a variable in a map clause of an enclosed construct may cause an implicit reference to the variable in the enclosing construct. Such implicit references are also subject to the data-sharing attribute rules outlined in this section.

A type parameter inquiry or complex part designator that is referenced in a construct is treated as if its designator is referenced.

Certain variables and objects have predetermined data-sharing attributes for the construct in which they are referenced. The ﬁrst matching rule from the following list of predetermined data-sharing attribute rules applies for variables and objects that are referenced in a construct.

Variables declared within a BLOCK construct inside a construct that do not have the SAVE attribute are private.

Variables and common blocks (in Fortran) that appear as arguments in threadprivate directives or variables with the _Thread_local (in C) or thread_local (in C++) storage-class speciﬁer are threadprivate.

Variables with automatic storage duration that are declared in a scope inside the construct are private.

Variables of non-reference type with automatic storage duration that are declared in a scope inside the construct are private.

Objects with dynamic storage duration are shared.

The loop iteration variable in the associated loop of a simd construct with just one associated loop is linear with a linear-step that is the increment of the associated loop.
The loop iteration variables in the associated loops of a simd construct with multiple associated loops are lastprivate.
The loop iteration variable in any associated loop of a loop construct is lastprivate.
The loop iteration variable in any associated loop of a loop-associated construct is otherwise private.

The implicitly declared variables of a range-based for loop are private.

Loop iteration variables inside parallel, teams, or task generating constructs are private in the innermost such construct that encloses the loop.
Implied-do, FORALL and DO CONCURRENT indices are private.

Variables with static storage duration that are declared in a scope inside the construct are shared.
If a list item in a map clause on the target construct has a base pointer, and the base pointer is a scalar variable that does not appear in a map clause on the construct, the base pointer is ﬁrstprivate.
If a list item in a reduction or in_reduction clause on the construct has a base pointer then the base pointer is private.
Static data members are shared.
The __func__ variable and similar function-local predeﬁned variables are shared.

Cray pointees have the same data-sharing attribute as the storage with which their Cray pointers are associated. Cray pointer support has been deprecated.
Assumed-size arrays and named constants are shared.
An associate name that may appear in a variable deﬁnition context is shared if its association occurs outside of the construct and otherwise it has the same data-sharing attribute as the selector with which it is associated.

Variables with predetermined data-sharing attributes may not be listed in data-sharing attribute clauses, except for the cases listed below. For these exceptions only, listing a predetermined variable in a data-sharing attribute clause is allowed and overrides the variable’s predetermined data-sharing attributes.

The loop iteration variable in any associated loop of a loop-associated construct may be listed in a private or lastprivate clause.
If a simd construct has just one associated loop then its loop iteration variable may be listed in a linear clause with a linear-step that is the increment of the associated loop.

Variables with const-qualiﬁed type with no mutable members may be listed in a firstprivate clause, even if they are static data members.
The __func__ variable and similar function-local predeﬁned variables may be listed in a shared or firstprivate clause.

Loop iteration variables of loops that are not associated with any OpenMP directive may be listed in data-sharing attribute clauses on the surrounding teams, parallel or task generating construct, and on enclosed constructs, subject to other restrictions.
Assumed-size arrays may be listed in a shared clause.
Named constants may be listed in a shared or firstprivate clause.

Additional restrictions on the variables that may appear in individual clauses are described with each clause in Section 5.4.

Variables with explicitly determined data-sharing attributes are those that are referenced in a given construct and are listed in a data-sharing attribute clause on the construct.

Variables with implicitly determined data-sharing attributes are those that are referenced in a given construct and do not have predetermined or explicitly determined data-sharing attributes in that construct.

Rules for variables with implicitly determined data-sharing attributes are as follows:

In a parallel, teams, or task generating construct, the data-sharing attributes of these variables are determined by the default clause, if present (see Section 5.4.1).
In a parallel construct, if no default clause is present, these variables are shared.
For constructs other than task generating constructs, if no default clause is present, these variables reference the variables with the same names that exist in the enclosing context.
In a target construct, variables that are not mapped after applying data-mapping attribute rules (see Section 5.8) are ﬁrstprivate.

In an orphaned task generating construct, if no default clause is present, formal arguments passed by reference are ﬁrstprivate.

In an orphaned task generating construct, if no default clause is present, dummy arguments are ﬁrstprivate.

In a task generating construct, if no default clause is present, a variable for which the data-sharing attribute is not determined by the rules above and that in the enclosing context is determined to be shared by all implicit tasks bound to the current team is shared.
In a task generating construct, if no default clause is present, a variable for which the data-sharing attribute is not determined by the rules above is ﬁrstprivate.

A program is non-conforming if a variable in a task generating construct is implicitly determined to be ﬁrstprivate according to the above rules but is not permitted to appear in a firstprivate clause according to the restrictions speciﬁed in Section 5.4.4.

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