SC15 Austin, TX

A Standard Debug Interface for OpenMP Target Regions

Authors: Andreas Erik Hindborg (Technical University of Denmark), Ignacio Laguna (Lawrence Livermore National Laboratory), Sven Karlsson (Technical University of Denmark), Dong H. Ahn (Lawrence Livermore National Laboratory)

Abstract: As OpenMP covers more on-node parallelism, debugging OpenMP programs is becoming challenging. Debuggers often debug OpenMP at a system-thread level, leaving programmers with limited state information on OpenMP threads. The OpenMP debugging interface, OMPD, has been proposed as a standard interface to overcome these limitations. However, the current specification works only for OpenMP 3.1 -- it cannot handle OpenMP 4.0 programs because it does not consider OpenMP target constructs. In this work, we study how to extend OMPD to OpenMP 4.0 and propose a set of OMPD extensions. We identify crucial scalability issues with the way OMPD currently represents threads and propose a new representation, Construction of Online Lightweight Thread handle, COLT, as a scalable solution. Our evaluation shows that our scheme is feasible as far as basic OMPD support is provided for OpenMP 4 runtime component and can also significantly reduce the memory and performance overheads of the debuggers.

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