Time Sharing Systems That Use a Partitioning Algorithm on Mesh-connected Parallel Computers

computers. Scheduling here is in principle moderate co-scheduling, with which the order of priority of the specic parallel processes is controlled per xed time. In addition, as a method to change the order of priority of parallel processes simultaneously for conducting co-scheduling, the authors proposed and installed internal synchronization which takes advantage of the synchronous clock that is a hardware property of AP1000+. Together with the communication library for polling/signal switching, this method allowed ecient execution of both ne grain parallel processes and coarse grain parallel processes. It was conrmed that co-scheduling allows ecient operation of busy wait communications of ne grain parallel processes, which wait for communication by busy wait, even when several of those are input. In addition , it was conrmed that the overall processing eciency of coarse grain parallel processes, which wait for communication by signal, could be improved by issuing context switching to execute another parallel process. Although the problem with internal synchronization is the co-scheduling skew caused by the failure of synchronization in the respective processors when conducting rescheduling , it was concluded that the time lag was negligible since it accounted for around 2.5% of 200 ms where priority switching takes place. The important issue of a parallel OS is to establish both a communication library and a scheduler in consideration of the properties of applications and the structures of the hardware available. A parallel OS designer must decide whether to use waiting by busy wait or context switching based on the communication patterns of the applications. If co-scheduling can eciently be installed on usable hardware, it is sucient to consider its introduction for ne grain parallel processes. At present, AP/Linux is compatible with both ne grain and coarse grain parallel processes, thus allowing ecient processing of a wide variety of application programs.