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OpenACC 3.4 Directives and Clauses

This comprehensive reference catalogue documents all OpenACC 3.4 keywords from the OpenACC Application Programming Interface Version 3.4 specification.

Purpose

This document serves as a complete keyword inventory for development and reference. Each entry includes:

  • Specification section and page numbers
  • Categorization and properties
  • No duplication - each keyword appears once

Coverage

  • 24 Directives/Constructs - All compute, data, loop, synchronization, declaration, and runtime directives (including space/underscore alias forms)
  • 50+ Clauses - All clause keywords
  • Modifiers - Data clause modifiers, gang/worker/vector modifiers, collapse modifiers
  • Special Values - Async values, device types, default values
  • Reduction Operators - All supported reduction operations
  • Parallelism Levels - Gang, worker, vector, seq

Directives and Constructs

Compute Constructs

  • parallel (§2.5.1; p.33; category: compute; association: block; properties: creates gang-worker-vector parallelism)
  • serial (§2.5.2; p.34; category: compute; association: block; properties: serialized execution on device)
  • kernels (§2.5.3; p.35; category: compute; association: block; properties: compiler-optimized kernel launch)

Data Constructs

  • data (§2.6.5; p.43; category: data; association: block; properties: structured data lifetime)
  • enter data (§2.6.6; p.45; category: data; association: executable; properties: dynamic data region entry)
  • exit data (§2.6.6; p.45; category: data; association: executable; properties: dynamic data region exit)
  • host_data (§2.8; p.62; category: data; association: block; properties: host pointer mapping)

Loop Constructs

  • loop (§2.9; p.64; category: loop; association: loop nest; properties: loop parallelization)
  • parallel loop (§2.11; p.75; category: combined; association: loop nest; properties: parallel + loop combined)
  • serial loop (§2.11; p.75; category: combined; association: loop nest; properties: serial + loop combined)
  • kernels loop (§2.11; p.75; category: combined; association: loop nest; properties: kernels + loop combined)

Synchronization Constructs

  • atomic (§2.12; p.77; category: synchronization; association: statement; properties: atomic memory operations)
  • cache (§2.10; p.75; category: synchronization; association: loop; properties: cache hint)
  • wait (§2.16.3; p.100; category: synchronization; association: executable; properties: async queue synchronization)

Declaration Directives

  • declare (§2.13; p.81; category: declarative; association: scope; properties: device data declaration)
  • routine (§2.15.1; p.91; category: declarative; association: function; properties: device routine declaration)

Runtime Directives

  • init (§2.14.1; p.84; category: runtime; association: executable; properties: device initialization)
  • shutdown (§2.14.2; p.85; category: runtime; association: executable; properties: device shutdown)
  • set (§2.14.3; p.87; category: runtime; association: executable; properties: runtime configuration)
  • update (§2.14.4; p.88; category: runtime; association: executable; properties: explicit data transfer)

Special Constructs

  • do concurrent (§2.17.2; p.102; category: integration; association: Fortran; properties: Fortran do concurrent mapping)

Clauses

Compute Clauses

  • if (§2.5.6; p.37; category: conditional; applicable to: parallel, serial, kernels, host_data, atomic, init, set, update)
  • self (§2.5.7; p.37; category: conditional; applicable to: parallel, serial, kernels; properties: execute on host without data movement)
  • async (§2.5.8, §2.16.1; pp.37, 99; category: synchronization; applicable to: parallel, serial, kernels, data, enter data, exit data, update, wait)
  • wait (§2.5.9, §2.16.2; pp.37, 100; category: synchronization; applicable to: parallel, serial, kernels, data, enter data, exit data, update)
  • num_gangs (§2.5.10; p.37; category: parallelism; applicable to: parallel, kernels; properties: specifies number of gangs)
  • num_workers (§2.5.11; p.38; category: parallelism; applicable to: parallel, kernels; properties: specifies workers per gang)
  • vector_length (§2.5.12; p.38; category: parallelism; applicable to: parallel, kernels; properties: specifies vector length per worker)
  • private (§2.5.13, §2.9.10; pp.38, 70; category: data sharing; applicable to: parallel, serial, kernels, loop)
  • firstprivate (§2.5.14; p.38; category: data sharing; applicable to: parallel, serial, kernels; properties: initialized private variables)
  • reduction (§2.5.15, §2.9.11; pp.39, 71; category: data sharing; applicable to: parallel, kernels, loop; properties: reduction operations)
  • default (§2.5.16; p.40; category: data sharing; applicable to: parallel, serial, kernels, data; properties: values are none or present)

Data Clauses

  • copy (§2.7.7; p.54; category: data movement; properties: copy in and copy out)
  • copyin (§2.7.8; p.55; category: data movement; properties: copy to device)
  • copyout (§2.7.9; p.56; category: data movement; properties: copy from device)
  • create (§2.7.10, §2.13.2; pp.57, 83; category: data allocation; properties: allocate on device)
  • no_create (§2.7.11; p.57; category: data allocation; properties: use if present, don’t create)
  • delete (§2.7.12; p.58; category: data allocation; properties: deallocate from device)
  • present (§2.7.6; p.53; category: data presence; properties: data must be present on device)
  • deviceptr (§2.7.5; p.53; category: data presence; properties: device pointer)
  • attach (§2.7.13; p.59; category: pointer; properties: attach pointer to device address)
  • detach (§2.7.14; p.59; category: pointer; properties: detach pointer from device address)

Synonyms: The specification preserves historical aliases such as pcopy, pcopyin, pcopyout, pcreate and their present_or_* counterparts. ROUP registers each alias alongside the canonical clause name so original source spellings are retained during parsing.

Host-Device Interaction Clauses

  • use_device (§2.8.1; p.63; category: host access; applicable to: host_data; properties: map device pointers to host)
  • if_present (§2.8.3; p.63; category: conditional; applicable to: host_data, update; properties: conditional on presence)

Loop Clauses

  • collapse (§2.9.1; p.65; category: loop transformation; applicable to: loop; properties: collapse nested loops)
  • gang (§2.9.2; p.66; category: parallelism; applicable to: loop; properties: gang-level parallelism)
  • worker (§2.9.3; p.68; category: parallelism; applicable to: loop; properties: worker-level parallelism)
  • vector (§2.9.4; p.68; category: parallelism; applicable to: loop; properties: vector-level parallelism)
  • seq (§2.9.5; p.68; category: parallelism; applicable to: loop; properties: sequential execution)
  • independent (§2.9.6; p.69; category: parallelism; applicable to: loop; properties: loop iterations are independent)
  • auto (§2.9.7; p.69; category: parallelism; applicable to: loop; properties: compiler decides parallelism)
  • tile (§2.9.8; p.69; category: loop transformation; applicable to: loop; properties: tile nested loops)
  • device_type (§2.9.9; p.70; category: device-specific; applicable to: loop, compute constructs; properties: device-specific clauses)

Declaration Clauses

  • device_resident (§2.13.1; p.82; category: data declaration; applicable to: declare; properties: data resides on device)
  • link (§2.13.3; p.84; category: data declaration; applicable to: declare; properties: static device linkage)

Special Clauses

  • finalize (§2.6.6; p.46; category: data management; applicable to: exit data; properties: force deallocation)
  • bind (§2.15.1; p.92; category: routine; applicable to: routine; properties: specify device routine name)
  • nohost (§2.15.1; p.93; category: routine; applicable to: routine; properties: routine only on device)

Modifiers

Modifiers are keywords that modify the behavior of clauses. They appear as part of clause syntax to refine clause semantics.

Data Clause Modifiers

  • always (§2.7.4; p.52; data clause modifier; forces data transfer even if present)
  • zero (§2.7.4; p.52; data clause modifier; zero memory on allocation)
  • readonly (§2.7.4; p.52; data clause modifier; read-only access)

Gang Clause Modifiers

  • num (§2.9.2; p.66; gang modifier; specifies number of gangs)
  • dim (§2.9.2; p.67; gang modifier; specifies gang dimension)
  • static (§2.9.2; p.67; gang modifier; static gang distribution)

Worker Clause Modifiers

  • num (§2.9.3; p.68; worker modifier; specifies number of workers)

Vector Clause Modifiers

  • length (§2.9.4; p.68; vector modifier; specifies vector length)

Collapse Clause Modifiers

  • force (§2.9.1; p.65; collapse modifier; force collapse even with dependencies)

Cache Clause Modifiers

  • readonly (§2.10; p.75; cache modifier; read-only cache hint)

Special Values and Constants

Async Values

  • acc_async_default (§2.16; p.98; async value; default async queue)
  • acc_async_noval (§2.16; p.98; async value; no async queue specified)
  • acc_async_sync (§2.16; p.98; async value; synchronous execution)

Device Types

  • * (§2.4; p.31; device type; all device types)
  • host (§2.4; p.31; device type; host device)
  • nvidia (§2.4; p.31; device type; NVIDIA devices)
  • radeon (§2.4; p.31; device type; AMD Radeon devices)
  • default (§2.4; p.31; device type; implementation default)

Default Clause Values

  • none (§2.5.16; p.40; default value; no implicit data sharing)
  • present (§2.5.16; p.40; default value; assume all data present)

Reduction Operators

Operators used with the reduction clause for parallel reduction operations.

Arithmetic Operators

  • + (§2.5.15, §2.9.11; pp.39, 71; addition)
  • * (§2.5.15, §2.9.11; pp.39, 71; multiplication)
  • max (§2.5.15, §2.9.11; pp.39, 71; maximum value)
  • min (§2.5.15, §2.9.11; pp.39, 71; minimum value)

Bitwise Operators

  • & (§2.5.15, §2.9.11; pp.39, 71; bitwise AND)
  • | (§2.5.15, §2.9.11; pp.39, 71; bitwise OR)
  • ^ (§2.5.15, §2.9.11; pp.39, 71; bitwise XOR)

Logical Operators

  • && (§2.5.15, §2.9.11; pp.39, 71; logical AND)
  • || (§2.5.15, §2.9.11; pp.39, 71; logical OR)

Fortran-Specific Operators

  • .and. (§2.5.15, §2.9.11; pp.39, 71; Fortran logical AND)
  • .or. (§2.5.15, §2.9.11; pp.39, 71; Fortran logical OR)
  • .eqv. (§2.5.15, §2.9.11; pp.39, 71; Fortran logical equivalence)
  • .neqv. (§2.5.15, §2.9.11; pp.39, 71; Fortran logical non-equivalence)
  • iand (§2.5.15, §2.9.11; pp.39, 71; Fortran bitwise AND)
  • ior (§2.5.15, §2.9.11; pp.39, 71; Fortran bitwise OR)
  • ieor (§2.5.15, §2.9.11; pp.39, 71; Fortran bitwise XOR)

Parallelism Levels

OpenACC defines a three-level parallelism hierarchy:

  • gang (§2.2.3; p.23; parallelism level; coarse-grain parallelism, analogous to thread blocks)
  • worker (§2.2.3; p.23; parallelism level; medium-grain parallelism, analogous to threads)
  • vector (§2.2.3; p.23; parallelism level; fine-grain parallelism, analogous to SIMD lanes)
  • seq (§2.9.5; p.68; parallelism level; sequential execution, no parallelism)

Atomic Operation Keywords

  • read (§2.12; p.77; atomic operation; atomic read)
  • write (§2.12; p.78; atomic operation; atomic write)
  • update (§2.12; p.78; atomic operation; atomic update)
  • capture (§2.12; p.79; atomic operation; atomic capture)

Runtime Clause Keywords

Set Directive Clauses

  • device_type (§2.14.3; p.87; applicable to: set; specifies device type)
  • device_num (§2.14.3; p.87; applicable to: set; specifies device number)
  • default_async (§2.14.3; p.87; applicable to: set; sets default async queue)

Update Directive Clauses

  • self (§2.14.4; p.88; applicable to: update; copy to host)
  • host (§2.14.4; p.88; applicable to: update; alias for self)
  • device (§2.14.4; p.88; applicable to: update; copy to device)

Routine Directive Clauses

  • gang (§2.15.1; p.92; applicable to: routine; routine contains gang-level parallelism)
  • worker (§2.15.1; p.92; applicable to: routine; routine contains worker-level parallelism)
  • vector (§2.15.1; p.92; applicable to: routine; routine contains vector-level parallelism)
  • seq (§2.15.1; p.92; applicable to: routine; routine is sequential)