The goal of the topology project is to develop methods and supporting tools that can automatically and intelligently assist science teams and their users in identifying the communication characteristics of their application, and categorizing them into job-types. At a high level, the potential categories of such a classification include near-neighbor-dominant, global-communication-dominant, communication-indifferent, etc.

 

Building upon the topology-aware mapping library developed during deployment of Blue Waters, we will add more capabilities, task mapping functions, and ease-of-use features to the tool. The most important among them is to transparently determine the scheduler job-type to which an application belongs (based on its communication behavior).

 

The new topology-aware scheduler on Blue Waters is expected to yield best results if the submitted jobs are able to correctly identify their communication characteristic category, and hence the utility of these tools that can assist users in finding the right job-type. For example, these tools will be useful in deciding if an application performs minimal communication and should be scheduled without regard for topology, or if  the application performs near-neighbor communication and should be allocated a compact partition whose communication is not affected by other jobs. The other important utility of these tools will be to help the application developers in identifying communication overheads and the performance bugs induced by them in their applications. Finally, these tools will help application users perform topology aware mapping of their codes at the job start up as well as during an execution if the application supports migration.