Programming Methods

High performance programming methods address systems of one or more processors that can be distributed within an SMP system or over the nodes of a cluster. These methods include: standard serial optimizations and library calls; auto-parallelization offered by some compilers, OpenMP directives, calls to the POSIX threads library, and calls to the message passing interface (MPI).

The overall parallel high performance program that takes advantage of multiple processors is still running a collection of single processor programs concurrently. Therefore, standard serial optimizations aimed at uniprocessor performance are important, including loop unrolling, cache blocking, and other coding techniques that allow the compilers to better optimize and pipeline programs.

By using multi-threading (OpenMP directives or Pthreads calls) and message passing (calls to an MPI library), the developer then achieves concurrency, where multiple parts of the program run simultaneously to achieve factors of performance improvement. Compiler auto-parallelization can be used to automatically generate multi-threading.

HP provides an MPI library that runs optimally on HP clusters in the HP-UX PA-RISC and Itanium, Linux IA32 and Itanium platform pairs. HP MPI is reliable, thread-safe, and fully compliant with the MPI-2 standard. HP MPI supports a variety of interconnect fabrics including TCP/IP, Quadrics Elan, Infiniband, and intranode communication. HP Visual MPI, a companion product of HP MPI, is an analysis tool that provides error detection and statistical analysis to highlight issues for improving performance.