Die geregelte logical Clock - Definition, Simulation und Anwendung. Eine globale Uhr fuer tracebasiertes Software-Monitoring paralleler Anwendungen in Workstation Clustern

Event tracing and monitoring of parallel applications are difficult if each processor has its own unsynchronized clock. A survey is given on several strategies to generate a global time, and their limits are discussed. The controlled logical clock is presented. It is new method based on Lamport's logical clock and provides a method to modify inexact timestamps of tracefiles. The new timestamps guarantee the clock condition, i.e. that the receive event of a message has a later timestamp than the send event. The corrected timestamps can also be used for performance measurements with pairs of events in different processes. The controlled logical clock is motivated and it is analyzed in detail by computer simulations. No additional protocol overhead is needed for the new method while tracing the application. It can be implemented as a filter for tracefiles or it can be integrated into monitor and debug tools for parallel applications. (orig.)SIGLEAvailable from TIB Hannover: RO 7298(30) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman