3

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 and Chapter 2.

This chapter discusses the following topics:

•HP XC application development environment overview (Section 3.1)

•Using compilers (Section 3.2)

•Getting system information (Section 3.3)

•Getting system information (Section 3.4)

•Setting debugging options (Section 3.5)

•Developing serial applications (Section 3.6)

•Developing parallel applications (Section 3.7)

•Developing libraries (Section 3.8)

•Advanced topics (Section 3.9)

3.1Overview

The HP XC cluster provides an application development environment that enables developing, building, and running applications using multiple nodes with multiple processors. These applications can be parallel applications using many processors, or serial applications using a single processor.

The HP XC cluster is made up of nodes that are assigned one or more various roles. Of importance to the application developer are the nodes that have the compute role and the login role (compute nodes and login nodes). Compute nodes run user applications. Login nodes are where you log in and interact with the system to perform various tasks, such as executing commands, compiling and linking applications, and launching applications. A login node can also execute single-processor 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 batch job scheduler to launch and manage parallel and serial applications. When a job is submitted, LSF places the job in a queue and allows it to run when the necessary resources become available. When a job is completed, LSF returns job output, job information, and any errors. In addition to batch jobs, LSF can also run interactive batch jobs and interactive jobs. An LSF interactive batch job is a batch job that allows you to interact with the application, yet still take advantage of LSF scheduling policies and features. An LSF interactive job is run without using LSF’s batch processing features, but is dispatched immediately by LSF on the LSF execution host node. LSF is described in detail in Chapter 7.

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.

Developing Applications 3-1