Directive Language Specification

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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