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:
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.
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.
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