HP XC System Software User's Guide Version 3.2

4 Developing Applications
This chapter discusses topics associated with developing applications in the HP XC environment.
Before reading this chapter, you should you read and understand Chapter 1 “Overview of the
User Environment” and Chapter 2 “Using the System”.
This chapter addresses the following topics:
• “Application Development Environment Overview” (page 43)
• “Compilers” (page 44)
• “Examining Nodes and Partitions Before Running Jobs” (page 45)
• “Interrupting a Job” (page 45)
• “Setting Debugging Options” (page 45)
• “Developing Serial Applications” (page 45)
• “Developing Parallel Applications” (page 46)
• “Developing Libraries” (page 50)
4.1 Application Development Environment Overview
The HP XC system provides an application development environment that enables developing,
building, and running applications using multiple nodes with multiple cores. These applications
can be parallel applications using many cores, or serial applications using a single core.
The HP XC system is made up of nodes that are assigned one or more roles. Nodes with the login
role (login nodes) and nodes with the compute role (compute nodes) are important to the
application developer:
• Compute nodes run user applications.
• Login nodes are where you log in and interact with the system to perform such tasks as
executing commands, compiling and linking applications, and launching applications. A
login node can also execute single-core applications and commands, just as on any other
standard Linux system.
Applications are launched from login nodes, and then distributed and run on one or more
compute nodes.
The HP XC environment uses the LSF-HPC batch job scheduler to launch and manage parallel
and serial applications. When a job is submitted, LSF-HPC places the job in a queue and allows
it to run when the necessary resources become available. When a job is completed, LSF-HPC
returns job output, job information, and any errors. In addition to batch jobs, LSF-HPC can also
run interactive batch jobs and interactive jobs. An LSF-HPC interactive batch job is a batch job
that allows you to interact with the application, yet still take advantage of LSF-HPC scheduling
policies and features. An LSF-HPC interactive job is run without using the batch processing
features of LSF-HPC, but is dispatched immediately by LSF-HPC on the LSF execution host
node. LSF-HPC is described in detail in Chapter 10 “Using LSF-HPC”.
Regardless of whether an application is parallel or serial, or whether it is run interactively or as
a batch job, the general steps to developing an HP XC application are as follows:
1. Build the code by compiling and linking with the correct compiler. Note that compiler
selection, and set up of appropriate parameters for specific compilers, is made easier by the
use of modules.
2. Launch the application with the bsub, srun, or mpirun command.
The build and launch commands are executed from the node to which you are logged in.
HP Unified Parallel C Support
HP XC System Software provides support for the HP Unified Parallel C (UPC) application
development environment.
4.1 Application Development Environment Overview 43