Cray Scientific Library (libsci) and Parallelism - Some Performance Aspects

Today, most of the Cray multiprocessor systems are still used within a multiprogramming environment. In such environments, there are two main issues contributing to whether or not production codes should exploit parallelism. Firstly, in terms of turnaround time, the parallel program should run faster than the single-tasked program version, and secondly, the costs, i.e. CPU-time from the user's point of view as well as system throughput from the computer center's point of view, should remain reasonably constant. This becomes even more important if parallelism is introduced automatically by calling optimized library routines provided by the vendor. The Cray Scientific Library (libsci) is such an example: The routines have to be highly efficient because these kernels are often used in user codes as basic blocks to build more complex algorithms. Based on libsci 7.0, the fieldtest version libsci 8.0 and the revised libsci 8.005, this report in detail describes performance values obtained f..