/claw-language-specification

Specification of the CLAW Directive Language

BSD 2-Clause "Simplified" LicenseBSD-2-Clause

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Directive Language Specification

Version

Reference Compiler

The CLAW Compiler is the reference compiler for the CLAW Directive Language. The project can be found here: claw-compiler

Versions

Specification document

The current specification can be found here: CLAW specification document

Generating the specification document

The specification is written using LaTeX. To generate the PDF document, you can use pdflatex with the following command:

cd documentation
pdflatex claw_language_specifications.tex
History
  • Version 0.1:
    • Define low-level block transformation.
      • Loop transformations.
      • Remove transformation.
  • Version 0.2:
    • Refine low-level transformation from 0.1 if needed.
      • Add collapse clause to loop-fusion directive.
    • Add missing low-level transformation from the requirements.
      • Add loop transformation loop-hoist.
      • Add array notation transformation array-transform.
      • Add claw transformation kcache for column caching.
      • Add claw transformation call for on the fly computation (array access to function call).
    • Start to abstract low-level transformation.
      • Introduction of the parallelize directive with the define dimension and forward clauses
  • Version 0.3:
    • Refine previous iterations, especially parallelize directive.
  • Version 0.4:
    • Refine previous iterations, especially parallelize directive.
    • Add conditional extraction if-extract
  • Version 1.1:
    • Clause cleanup added to loop-hoist directive
  • Version 2.0
    • Specify how ELEMENTAL function behave with SCA.
    • Introducing Model Configuration
    • Introducing model-data directive for SCA
    • parallelize clause is renamed by sca
    • New low-level directive loop-fission
    • Directive array-transform is renamed expand
    • New clause blocked and block-fct added to sca foward

General information about the CLAW language

The directives are either local or global.

  • Local directive: those directives have a limited impact on a local block of code (for example, only in a subroutine)
  • Global directive: those directives can have an impact on the whole application.

This language is separated in the followings sections:

  • CLAW abstraction (specific abstraction for climate system modeling build on the top of other directives)
    • k caching (column caching)
    • on the fly computation (array access to function call)
    • Single Column Abstraction (SCA)
  • Loop transformation
    • loop fusion
    • loop interchange/reordering
    • loop extraction
    • loop hoisting
    • loop fission
    • conditional extraction
  • OpenACC/OpenMP abstractions/helpers
    • array notation to do statement
    • conditional primitive directive
  • Utilities
    • remove
    • ignore
    • verbatim
Line continuation

CLAW directives can be defined on several line. The syntax is described in the listing below:

!$claw directive options &
!$claw options
Interpretation order of the CLAW directives

The claw directives can be combined together. For example, loop-fusion and loop-interchange can be used together in a group of nested loops.

The interpretation order of the directives is the following:

  1. ignore
  2. remove
  3. primitive
  4. array-transform
  5. loop-extract
  6. loop-hoist
  7. loop-fusion
  8. loop-fission
  9. loop-interchange
  10. on-the-fly
  11. kcache
  12. if-extract
  13. sca
  14. formatting transformation (internal transformation only)

Users must be aware that directives transformation are applied sequentially and therefore, a transformation can be performed on already transformed code.

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