Abstract. Debugging is often the most time consuming part of software development. HPC applications prolong the debugging process by adding more processes interacting in dynamic ways for longer periods of time. Checkpoint/restart-enabled parallel debugging returns the developer to an intermediate state closer to the bug. This focuses the debugging process, saving developers considerable amounts of time, but requires parallel debuggers cooperating with MPI implementations and checkpointers. This paper presents a design specification for such a cooperative relationship. Additionally, this paper discusses the application of this design to the GDB and DDT debuggers, Open MPI, and BLCR projects.
Performance engineers are beginning to explore software-level optimisation as a means to reduce the energy consumed when running their codes. This paper presents POSE, a mathematical and visual modelling tool which highlights the relationship between runtime and power consumption. POSE allows developers to assess whether power optimisation is worth pursuing for their codes.We demonstrate POSE by studying the power optimisation characteristics of applications from the Mantevo and Rodinia benchmark suites. We show that LavaMD has the most scope for CPU power optimisation, with improvements in Energy Delay Squared Product (ED 2 P) of up to 30.59%. Conversely, MiniMD offers the least scope, with improvements to the same metric limited to 7.60%. We also show that no power optimised version of MiniMD operating below 2.3 GHz can match the ED 2 P performance of the original code running at 3.2 GHz. For LavaMD this limit is marginally less restrictive at 2.2 GHz.
In this paper we investigate the practical viability of PRAM programming within the BSP framework. We argue that there is a necessity for PRAM computations in situations where the problem exhibits poor data locality. We introduce a C++ PRAM simulator that is built on top of the Oxford BSP Toolset, BSPlib, and provide a succinct PRAM language. Our approach achieves simplicity of programming over direct-mode BSP programming for reasonable overhead cost. We objectively compare optimized BSP algorithms with PRAM algorithms implemented with our library and provide encouraging experimental results for the latter style of programming.
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