NASA
High Performance Computing
and Communications Program

Computational AeroSciences Project

NTV - The NAS Trace Visualizer

Objective: The objective is to develop a programming tool aimed at supporting high performance computing on scalable parallel computers. NTV focuses on performance and correctness by helping to detect performance bottle-necks using scalable visual representations of execution traces and innovative trace-browsing capabilities.

Approach: Program developers are faced with a number of computational platforms. Each platform has its own peculiarities which effect the way code is tuned for optimum performance. One of the more useful techniques available for tuning is the analysis of executions traces. Some manufacturers provide a tracing capability but some do not, requiring the use of an instrumentor such as that provided by AIMS. The quantity and complexity of trace data make graphical trace visualizers essential for analysis. Unfortunately, all existing trace visualizers are designed to handle only a specific trace format, and the formats differ among manufacturers and instrumentors. Further, the visualizers differ in function and in operation, so program developers are forced to become proficient with several analysis tools. NTV is a trace visualization tool designed to be used with all trace formats so that a user need only learn one tool. Further, unlike existing visualizers, it uses static displays which are easier to understand and more scalable than the dynamic displays common in other visualizers. In order to exploit the capabilities of NTV, the components of NTV are available as a library of display elements (Ben) that can be used to develop specialized visualizers while maintaining a common user interface.

The figure shows the major components of Ben. The displays use data from a program running on an IBM SP and using MPI for communications.

Accomplishments: A Beta version supporting AIMS traces and IBM SP2 MPL was released. Ben was developed and preliminary testing completed. The time line display in Ben was enhanced over that in NTV to support the visualization of some data not common in traces but provided by AIMS capabilities. NTV was ported to visualize IBM SP MPI traces.

Significance: With release of the Beta version the tool is now available to help users develop efficient parallel programs. It has been demonstrated that a tool can be developed that supports very different trace formats, and that static displays can be supported on existing workstations. The extension to IBM SP MPI and the production of Ben has extended the usefulness of the work. Status/Plans: Maintain and support the released version of NTV. Develop a replacement of visualizer for AIMS using Ben.

Point(s) of Contact:

Louis Lopez
NASA Ames Research Center
llopez@nas.nasa.gov
415-604-0521