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Application of VisAll in the Plosys system

In order to apply the VisAll tool to the Plosys system, two new files were created: trace.c e trace.h. These files implement the functions that store the VisAll events. Each worker generates a totally ordered tracefile. The set of tracefiles generated by all workers are merged in a single file also totally ordered. The following Plosys programs were instrumented to generate trace events: wam_engine.c e worker.c. The C application file also must emit an event corresponding to successful completion of a branch.

We faced a problem with the instrumentation given that the Plosys system runs in a totally distributed environment and therefore lacks a global clock. We had two alternatives to implement a global clock: to use synchronisation of the physical clock or synchronisation of a logical clock. The algorithm used to obtain a logical global clock is the one proposed by Lamport [68].



Ines de Castro Dutra
1999-05-04