Overview of the Project

The Lightweight Corefile Browser (LCB) is an X Window System based tool that facilitates parallel debugging. It offers a simple and convenient way of examining the dynamic call graph of a parallel program. It offers a global, high-level view of the program's state when it terminated.

LCB supports two modes of operation

The graphical version, xlcb, allows navigation through the potentially complex calling hierarchy of the program. It automatically assimilates the details from tens or hundreds of processes and presents them in a consolidated summary form representing the dynamic call graph of a parallel application. The command line version, lcb, allows the user to retrieve the most critical information via a textual interface. Thus, the user can obtain a minimal amount of information very quickly, without the start-up time associated with the graphical version. This not only saves time, but also supports dial-up connections and other uses where graphical facilities are not available.

LCB gets the necessary information from a lightweight corefile (LCF), an ASCII file generated by parallel runtime systems supporting the LCF format. LCB can also accept information on-the-fly from the operating system or some other tool. To do this, a minimal amount of data is recorded for each process at the point of program termination, and formatted according to the LCF standard.

The command line version offers the ability to:

The graphical version has, in addition, the ability to: Both command line and graphical versions have been implemented. The LCB display has been integrated into Meiko's TotalView debugger, allowing the user to view the calling structure of a program at any given execution point. The tool can also be invoked in standalone mode, using input files from Intel's corefile format.

The functionality to be incorporated in the tool, and the appearance of the interface were decided by involving users throughout the design process. Initial feedback was received in response to a "paper design" presented at a Parallel Tools Consortium general meeting. A working committee was then set up, involving both tool developers and tool users. Ideas and solutions were discussed electronically by the committee members. An initial prototype was tested at the National Center for Atmospheric Research and user suggestions were incorporated into the tool. Additional feedback was obtained when tool was exhibited at Supercomputing `94, and through user trials of the TotalView implementation.

Last updated February 23, 1996.
For further information, contact ptools-questions@nero.net.