Overall Objectives
Research Program
Application Domains
Software and Platforms
New Results
Bilateral Contracts and Grants with Industry
Partnerships and Cooperations
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Section: New Results

The Multifor programming construct

We have proposed a new programming control structure called “multifor”, allowing to take advantage of optimization and parallelization opportunities that are not easily attainable using the standard programming structures.

In a multifor-loop, several loops whose bodies are run in interleaved fashion can be defined. Respective iteration domains are mapped onto each other according to a run frequency – the grain – and a relative position – the offset. Imen Fassi developped a source-to-source compiler called IBB (Iterate-But-Better) which is automatically translating any C source code containing multifor-loops into an equivalent source code where multifor-loops have been transformed into equivalent for-loops. Traditional polyhedral software tools, and particularly CLooG [21] , are used to generate the corresponding code. Additionally, a promising perspective related to non-linear mapping of iteration spaces has also been developed, yielding to run a loop nest inside any other one by solving the problem of inverting “ranking Ehrhart polynomials”.

This work is the PhD work of Imen Fassi, who started her work in 2013 and who is co-advised by Yosr Slama, Assistant Professor at the University El Manar in Tunis, Tunisia, and Philippe Clauss. A first paper [15] on this topic has been published at the IMPACT workshop that was held in conjunction with the HIPEAC conference in Berlin, Germany, in January 2013. Another paper describing the IBB compiler and showing the efficiency of multifor codes has been submitted to an international conference.

Obviously, reasoning on such a syntactic sugar suppose an associated precise and unambiguous meaning. Therefore a denotational semantics has been defined that resolves all such semantic issues and that is well-suited to prove code transformations. It has been presented to the French community of Compilation during the sixth meeting in Annecy ( ).