ﬁrstprivate Clause

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

5.4.4 firstprivate Clause


Name: firstprivate	Properties: data-environment attribute, data-sharing attribute, privatization

Arguments


Name	Type	Properties

list	list of variable list item type	default

Directives

Semantics

The firstprivate clause provides a superset of the functionality provided by the private clause. A list item that appears in a firstprivate clause is subject to the private clause semantics described in Section 5.4.3, except as noted. In addition, the new list item is initialized from the original list item that exists before the construct. The initialization of the new list item is done once for each task that references the list item in any statement in the construct. The initialization is done prior to the execution of the construct.

For a firstprivate clause on a construct that is not a work-distribution construct, the initial value of the new list item is the value of the original list item that exists immediately prior to the construct in the task region where the construct is encountered unless otherwise speciﬁed. For a firstprivate clause on a work-distribution construct, the initial value of the new list item for each implicit task of the threads that execute the construct is the value of the original list item that exists in the implicit task immediately prior to the point in time that the construct is encountered unless otherwise speciﬁed.

To avoid data races, concurrent updates of the original list item must be synchronized with the read of the original list item that occurs as a result of the firstprivate clause.

For variables of non-array type, the initialization occurs by copy assignment. For an array of elements of non-array type, each element is initialized as if by assignment from an element of the original array to the corresponding element of the new array.

For each variable of class type:

If the firstprivate clause is not on a target construct then a copy constructor is invoked to perform the initialization; and
If the firstprivate clause is on a target construct then how many copy constructors, if any, are invoked is unspeciﬁed.

If copy constructors are called, the order in which copy constructors for diﬀerent variables of class type are called is unspeciﬁed.

If the original list item does not have the POINTER attribute, initialization of the new list items occurs as if by intrinsic assignment unless the original list item has a compatible type-bound deﬁned assignment, in which case initialization of the new list items occurs as if by the deﬁned assignment. If the original list item that does not have the POINTER attribute has the allocation status of unallocated, the new list items will have the same status.

If the original list item has the POINTER attribute, the new list items receive the same association status as the original list item, as if by pointer assignment.

The list items that appear in a firstprivate clause may include named constants.

Restrictions

Restrictions to the firstprivate clause are as follows:

A list item that is private within a parallel region must not appear in a firstprivate clause on a worksharing construct if any of the worksharing regions that arise from the worksharing construct ever bind to any of the parallel regions that arise from the parallel construct.
A list item that is private within a teams region must not appear in a firstprivate clause on a distribute construct if any of the distribute regions that arise from the distribute construct ever bind to any of the teams regions that arise from the teams construct.
A list item that appears in a reduction clause of a parallel construct must not appear in a firstprivate clause on a worksharing, task, or taskloop construct if any of the worksharing or task regions that arise from the worksharing, task, or taskloop construct ever bind to any of the parallel regions that arise from the parallel construct.
A list item that appears in a reduction clause of a teams construct must not appear in a firstprivate clause on a distribute construct if any of the distribute regions that arise from the distribute construct ever bind to any of the teams regions that arise from the teams construct.
A list item that appears in a reduction clause of a worksharing construct must not appear in a firstprivate clause in a task construct encountered during execution of any of the worksharing regions that arise from the worksharing construct.

∙ A variable of class type (or array thereof) that appears in a firstprivate clause requires an accessible, unambiguous copy constructor for the class type. ∙ If the original list item in a firstprivate clause on a work-distribution construct has a reference type then it must bind to the same object for all threads in the binding thread set of the work-distribution region.

∙ If the list item is a polymorphic variable with the ALLOCATABLE attribute, the behavior is unspeciﬁed.

Cross References

distribute directive, see Section 11.6
do directive, see Section 11.5.2
for directive, see Section 11.5.1
parallel directive, see Section 10.1
private clause, see Section 5.4.3
scope directive, see Section 11.2
sections directive, see Section 11.3
single directive, see Section 11.1
target directive, see Section 13.8
task directive, see Section 12.5
taskloop directive, see Section 12.6
teams directive, see Section 10.2

[next] [prev] [prev-tail] [front] [up]