Since processor counts in supercomputers are increasing dramatically, efficient interprocessor communication is becoming even more important for the applications that run on them. A high level, abstract understanding of an application's communication behavior would not only simplify debugging of that communication but would also support more directed performance optimization. We explore automated identification of communication patterns to provide that high level abstraction. We introduce an algorithm to extract communication patterns from MPI traces automatically. Our algorithm first finds locally repeating sequences and then iteratively grows them into global patterns. We demonstrate our technique on three realistic codes using traces from up to 128 processors. Our results show that our approach detects the underlying communication pattern within reasonable time andmemory constraints, even for large trace sizes.

Scalability and complexity of HPC software requires corresponding support from program analysis tools capable of dealing with possibly huge amounts of data. E.g., MPI traces capture low-level communication behavior essential to understand program behavior, but are typically too detailed and large and hence need to be reduced, pre-processed, and mapped to a higher level of abstraction before being comprehensible by human users. One possible approach is to utilize the occurrence of patterns in the execution of a program for the benefits of the user's understanding. Such patterns can be either user-defined or automatically extracted from program traces, requiring minimal interaction from users. This poster describes such an enhanced approach to pattern detection in program traces, which is available within a program analysis framework. In addition, the poster reports about patterns in existing, realistic applications and the pattern detection mechanism to extract useful information about a program's behavior.

A lightweight JPEG 2000 encryption scheme for mobile environments, based on wavelet filter parametrization, is discussed. Being a special variant of header encryption, the technique has an extremely low computational demand. Compression quality and security assessment show that the scheme may be employed in applications requiring a low to medium security level, provided the conditions for a secure use discussed in this work are obeyed