BBN Advanced Computers Inc of Cambridge, Massachusetts, has added a Butterfly Lisp compiler, claiming it to be the first large-scale shared memory multiprocessor implementation of Common Lisp. The Bolt Beranek & Newman subsidiary formed to develop and manufacture massively parallel processors says that the high-level language running on the Butterfly parallel processor preserves the natural shared memory characteristic of Lisp. Butterfly Lisp supports Scheme and Common Lisp dialects in both interpreted and compiled modes, and BBN has extended it to support a multiprocessing environment. A mechanism called future allows a process to create multiple parallel computations that are automatically distributed to other processors and also provides automatic synchronisation, enabling the programmer to develop parallel code as he would with conventional Lisp programs. This implementation of Lisp is part of BBN’s strategy to provide a computer that seems like a conventional system, but has the power of an extraordinary computer, Paul Castleman, president of BBN Advanced Computers, said. Butterfly Lisp allows a single Lisp program or multiple programs to run on up to 256 tightly coupled processors. A performance analysis facility is included in the implementation that enables programmers to analyse the dynamic behaviour of programs to help debugging and improve program performance. The facility graphically displays the evolution of an algorithm once it is run on the Butterfly system, enabling the programmer to identify threads of parallel control and the interactions among them. A mouse can be used to point to a thread of control in order to display the source code that created it. Run-time information about the state of each processor is displayed graphically. BBN adds that status information is available for the numbers of tasks waiting to be executed, effective processor usage and the rate of memory consumption. C language primitives can be called from Butterfly Lisp to solve complex mathematical equations such as fast fourier transforms. BBN Advanced Computers plans to put Butterfly Lisp into beta test in September, and will be priced at $12,000.
