Experimentation and Extension of a Specification Language of the Communications for Distributed Computation
Résumé
Explicit parallelism relies on transmissions of messages between processes. However, as workstations are not intended to manage this kind of communications, it is necessary to use communication libraries, known as Message Passing, which ensure data exchanges between parallel tasks of a same application. Currently, only MPI (Message Passing Interface) is still used, and its use became more complex. In order to solve this problem, a new language called MeDLey was developed ; its purpose is to allow the users an easier parallelism programming based on communications using Message Passing. MeDLey is an attempt to provide an abstract language to specify the communications of a distributed application independently from any current underlying communication layer. Based on this specification, a MeDLey compiler will generate several levels of implementation for all communication primitives : a first implementation based on PVM or MPI code, and a second one, more specific, more efficient, directly implemented on top of a network layer, or a more specific communication layer (active messages, shared memory, e.g.) to bypass the overhead introduced by message passing libraries. As for any data-processing tool, the experimentation of the MeDLey language was of obvious need, therefore the topic of this work whose aim initially is to experiment this language on real example, then to propose some extensions which prove to be necessary in the applications based on communications by Message Passing. This work is completed within team RESEDAS (Computer networks and Distributed systems) with the CRIN-CNRS & INRIA Lorraine within the framework of a collaboration with the Center Charles Hermite (Lorraine Center of Competence in Modeling and Calculation with High Performance). In this paper, we will first overview the basics of the MeDLey syntax and semantics, before talking about the experimentation and extension parts of this language.