Operational Semantics for PLEX A Basis for Safe Parallelization

Sammanfattning: The emerge of multi-core computers implies a major challenge for existing software. Due to simpler cores, the applications will face decreased performance if not executed in parallel. The problem is that much of the software is sequential.Central parts of the AXE telephone exchange system from Ericsson is programmed in the language PLEX. The current software is executed on a single-processor architecture, and assumes non-preemptive execution.This thesis presents two versions of an operational semantics for PLEX; one that models execution on the current, single-processor, architecture, and one that models execution on an assumed shared-memory architecture. A formal semantics of the language is a necessity for ensuring correctness of program analysis, and program transformations.We also report on a case study of the potential memory conflicts that may arise when the existing code is allowed to be executed in parallel. We show that simple static methods are sufficient to resolve many of the potential conflicts, thereby reducing the amount of manual work that probably still needs to be performed in order to adapt the code for parallel processing.