A new software tool designed to help users optimise the execution of programs on the Butterfly family of parallel processing systems, BBN Advanced Computers Inc has been developed at Indiana University. The Blaze Editor, or Bled, is a public domain program which the devlopers claim helps programmers optimise parallel programs, ensuring that users are getting the best performance from their multiprocessing systems. Normally, the task of porting code to a parallel machine requires the user to recode and restructure the algorithm to make it work well. There are several automatic paralleling systems that facilitate this process, but many users prefer to improve performance beyond what these automatic systems provide. Bled is an interactive program editing and transformation system that helps the user improve performance. The system consists of a user interface manager that provides the user with several tools, including program editing, transformation and evaluation tools, which can be applied to selected parts of the program. The user works with Bled to restructure the code for the Butterfly architecture and monitor this transformation. If the user attempts to transform the program in violation of the original code semantics, the system warns that a change in the meaning of the program has occurred. The user can ask the system what legal parallelising transformation can be applied to a segment of the selected code or can ask the system to make the desired program modifications, thus ensuring the correctness of the code. Bled is also being designed to make estimates of potential program execution behaviour, providing the programmer with feedback about the suitability of algorithm constructs and problems that may be encountered during execution. When the code is actually running on a Butterfly, the user can switch to a performance evaluation package to do final fine tuning. The Indiana University researchers now are working with CRSD at the University of Illinois in Urbana and researchers at INRIA in Paris on two extensions to the system. One is the performance prediction package mentioned. The other is a portable run-time environment supporting a dynamic microtasking facility that incorporates ideas from the Argonne Schedule package and the Massachusetts Institute of Technology multiLisp system.
