DEPEND Clause

dependence-type

Can be any one of the following clauses: IN, OUT, or INOUT.

For IN, the generated task will be a dependent task of all previously generated sibling tasks that reference at least one of the list items in an OUT or INOUT clause.

For OUT and INOUT, the generated task will be a dependent task of all previously generated sibling tasks that reference at least one of the list items in an IN, OUT, or INOUT clause.

list

Is one or more variables or non-zero length array sections. Any list items used in a DEPEND clause of the same task or sibling tasks must indicate identical storage or disjoint storage. The list items that appear in the DEPEND clause may include array sections.

Note that this enforced task dependence establishes a synchronization of accesses to each list item performed by a dependent task, with respect to accesses to the same list item performed by any previous tasks. You must properly synchronize access with respect to other concurrent accesses to each list item.

SOURCE

Specifies the satisfaction of cross-iteration dependences that arise from the current iteration.

SINK

Specifies a cross-iteration dependence, where the iteration vector vec indicates the iteration that satisfies the dependence.

vec

Is the iteration vector. It has the form:

where n is the value specified by the ORDERED clause in the DO loop directive, x_i denotes the loop iteration variable of the i-th nested loop associated with the loop directive, and d_i is a non-negative integer scalar constant.

If vec does not occur in the iteration space, the DEPEND clause is ignored. Note that if vec does not indicate a lexicographically earlier iteration, it can cause a deadlock.

For a vec element form of x_i + d_i or x_i - d_i, the expression x_i + d_i or x_i - d_i for any value of the integer loop iteration variable x_i that can encounter the ordered construct must be computable in the loop iteration variable's type without overflow.