5.4.6  linear Clause

Arguments

Modifiers

Directives

Additional information

Semantics

When a linear clause is specified on a construct, the value of the new list item on each logical iteration of the associated loops corresponds to the value of the original list item before entering the construct plus the logical number of the iteration times linear-step. The value corresponding to the sequentially last logical iteration of the associated loops is assigned to the original list item.

When a linear clause is specified on a declare simd directive, the list items refer to parameters of the procedure to which the directive applies. For a given call to the procedure, the clause determines whether the SIMD version generated by the directive may be called. If the clause does not specify the ref linear-modifier, the SIMD version requires that the value of the corresponding argument at the callsite is equal to the value of the argument from the first lane plus the logical number of the lane times the linear-step. If the clause specifies the ref linear-modifier, the SIMD version requires that the storage locations of the corresponding arguments at the callsite from each SIMD lane correspond to locations within a hypothetical array of elements of the same type, indexed by the logical number of the lane times the linear-step.

Restrictions

• Only a loop iteration variable of a loop that is associated with the construct may appear as a list item in a linear clause if a reduction clause with the inscan modifier also appears on the construct.
• A linear-modifier may be specified as ref or uval only on a declare simd directive.
• For a linear clause that appears on a loop-associated construct, the difference between the value of a list item at the end of a logical iteration and its value at the beginning of the logical iteration must be equal to linear-step.
• If linear-modifier is uval for a list item in a linear clause that is specified on a declare simd directive and the list item is modified during a call to the SIMD version of the procedure, the program must not depend on the value of the list item upon return from the procedure.

• If linear-modifier is uval for a list item in a linear clause that is specified on a declare simd directive, the program must not depend on the storage of the argument in the procedure being the same as the storage of the corresponding argument at the callsite.

  ∙ All list items must be of integral or pointer type. ∙ If specified, linear-modifier must be val.
  ∙ If linear-modifier is not ref, all list items must be of integral or pointer type, or must be a reference to an integral or pointer type. ∙ If linear-modifier is ref or uval, all list items must be of a reference type. ∙ If a list item in a linear clause on a worksharing construct has a reference type then it must bind to the same object for all threads of the team. ∙ If a list item in a linear clause that is specified on a declare simd directive is of a reference type and linear-modifier is not ref, the difference between the value of the argument on exit from the function and its value on entry to the function must be the same for all SIMD lanes.
  ∙ If linear-modifier is not ref, all list items must be of type integer. ∙ If linear-modifier is ref or uval, all list items must be dummy arguments without the VALUE attribute. ∙ List items must not be Cray pointers or variables that have the POINTER attribute. Cray pointer support has been deprecated. ∙ If linear-modifier is not ref and a list item has the ALLOCATABLE attribute, the allocation status of the list item in the sequentially last iteration must be allocated upon exit from that iteration. ∙ If linear-modifier is ref, list items must be polymorphic variables, assumed-shape arrays, or variables with the ALLOCATABLE attribute. ∙ If a list item in a linear clause that is specified on a declare simd directive is a dummy argument without the VALUE attribute and linear-modifier is not ref, the difference between the value of the argument on exit from the procedure and its value on entry to the procedure must be the same for all SIMD lanes. ∙ A common block name must not appear in a linear clause.

Cross References

• declare simd directive, see Section 7.7
• do directive, see Section 11.5.2
• for directive, see Section 11.5.1
• private clause, see Section 5.4.3
• simd directive, see Section 10.4
• taskloop directive, see Section 12.6