Network-specific performance enhancements for PVM

PVM, a message-passing software system for parallel processing, is used on a wide variety of processor platforms, but this portability restricts execution speed. The work here will address this problem mainly in the context of Ethernet-based systems, proposing two PVM enhancements for such systems. The first enhancement exploits the fact that an Ethernet has broadcast capability. Since unenhanced PVM must, to keep portability, avoid using broadcast, execution speed is sacrificed. In addition, the larger the system, the larger the sacrifice in speed. A solution to this problem is presented. The second enhancement is intended for use in applications in which many concurrent tasks finish at the same time, and thus simultaneously try to transmit to a master process. On an Ethernet, this produces excessively long random backoffs, reducing program speed. An enhancement, termed "programmed backoff," is proposed.