Planning Volume 2, Control Workstation and Software Environment

Planning for Parallel Environment

The IBM Parallel Environment for AIX program product is designed to help you develop parallel programs and execute them on the SP system or a networked cluster of RS/6000 processors.

The main Parallel Environment components are:

• The Communications Low-Level Application Programming Interface (LAPI), which is designed to provide optimal communication performance on the SP Switch. It does not support the SP Switch2.
• Message Passing and Collective Communications Application Programming Interface (API) Subroutine Library, which helps application developers parallelize their code.
• Parallel Operating Environment, which provides the ability to create and execute parallel application programs.
• Parallel Debuggers, which assist in debugging parallel applications.
• Visualization Tool, a trace generation and display system to visualize performance characteristics of your program and system.

Nodes operating with PSSP 2.3 or later and AIX 4.2.1 or later, support the Parallel Environment. Parallel Environment 2.4 or later has support for the Message Passing Library (MPL) subroutines, the Message Passing Interface (MPI) standard, and the Low Level Applications Programming Interface (LAPI). |If you plan to develop applications using the LAPI component of PSSP |3.4, you must use Parallel Environment 3.1 or later. See Chapter 11, Planning for migration for more release level compatibility |information.

Be aware that parts of the Parallel Environment installation steps might interact with or be affected by PSSP component installations, particularly the switch services component of PSSP (ssp.css) and the SP security services (ssp.clients). See the book PE: Installation Guide for details on planning for and installing Parallel Environment, particularly if you are interested in any of the following:

• Installing Parallel Environment on a control workstation.
• Installing Parallel Environment to run off the rack, with the ssp.clients file set.
• Installing the switch services component of PSSP (ssp.css) after Parallel Environment has been installed.

Be sure to address the following considerations:

1. Ticket and credentials lifetimes.
2. What ticket and credential lifetimes need to be set with respect to PE and LoadLeveler. The lifetime needs to be long enough to allow for the expected longest running job to complete.
3. DCE server replication when large numbers of tasks are to be used.
4. The DCE user id is used if it is different from the AIX user id. IBM suggests you use DCE integrated login.