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ChaNGa is an N-body cosmology simulation application implemented using Charm++. In this paper, we present the parallel design of ChaNGa and address many challenges arising due to the high dynamic ranges of clustered datasets. We propose optimizations based on adaptive techniques. We evaluate the performance of ChaNGa on highly clustered datasets: a z ∼ 0 snapshot of a 2 billion...
Fine-grained communication in supercomputing applications often limits performance through high communication overhead and poor utilization of network bandwidth. This paper presents Topological Routing and Aggregation Module (TRAM), a library that optimizes fine-grained communication performance by routing and dynamically combining short messages. TRAM collects units of fine-grained communication...
Charisma is a higher-level notation for writing parallel static data flow programs. It provides a convenient publish-consume paradigm for the expression of static flows of data and control. Although the syntax of the language allows the elegant expression of an important class of programs, it is restrictive, in that not all types of static data flow program can be written in Charisma. In this paper,...
With the growing amount of parallelism available on today's multicore processors, achieving good performance at scale is challenging. We approach this issue through an alternative to traditional thread-based paradigms for writing shared memory programs, namely message driven multicore programming. We study a number of optimizations that improve the efficiency of message driven programs on multicore...
State space search problems abound in the artificial intelligence, planning and optimization literature. Solving such problems is generally NP-hard. Therefore, a brute-force approach to state space search must be employed. It is instructive to solve them on large parallel machines with significant computational power. However, writing efficient and scalable parallel programs has traditionally been...
The first Teraflop/s computer, the ASCI Red, became operational in 1997, and it took more than 11 years for a Petaflop/s performance machine, the IBM Roadrunner, to appear on the Top500 list. Efforts have begun to study the hardware and software challenges for building an exascale machine. It is important to understand and meet these challenges in order to attain Exaflop/s performance. This paper...
This paper focuses on the use of GPGPU-based clusters for hierarchical N-body simulations. Whereas the behavior of these hierarchical methods has been studied in the past on CPU-based architectures, we investigate key performance issues in the context of clusters of GPUs. These include kernel organization and efficiency, the balance between tree traversal and force computation work, grain size selection...
The expression of parallel codes through abstract, high-level specifications of global control and data flow can greatly simplify the task of creating large parallel programs. We discuss the challenges of compiling such global flows into the behavioral descriptions of individual component objects in an SPMD environment. We present our work in the context of Charisma, a language that describes global...
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