Exam 4- 2013

Symp on performance analysis of systems and software

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Unformatted text preview: ulti-Threaded Apber of cores for blackscholes, facesim (both plications,” in Int’l. Symp. on Performance Analysis of Systems and Software (ISPASS), 2012. PARSEC) and cholesky (SPLASH-2). Part A (5 points) allel programming has become inevitable exhibit strong Which, if any, of the three applicationsfor mainstream scalability? Explain your answer. computing. One of the key needs to efficient programming is to have the appropriate tools to analyze parallel performance. In particular, a software developer needs analysis tools to identify the performance scaling bottlenecks, not only on current hardware but also on future hardware with many more cores than are available today; likewise, computer architects need analysis tools to understand the behavioral characteristics of existing and future workloads to design and optimize future hardware. Speedup curves which report speedup as a function of the number cores, as exemplified in Figure 1, are often used to understand scaling behavior of an application. Although Part B (5 points) a high-level view on application scala speedup curve gives ing behavior, it does not provide any insight with respect cholesky at 16 threads? Please show enough What is the approximate efficiency of facesim and to why to make clear how does not scale. your answer. work an application does oryou arrived at There are many possible causes for poor scaling behavior, such as synchronization, as well as interference in both shared on-chip resources (e.g., last-level cache) and off-chip resources (e.g., main memory). Unfortunately, a speedup curve provides no clue whatsoever why an application exhibits poor scaling behavior. In this paper, we propose the speedup stack which is a novel representation that provides insight into an application’s scaling behavior on multi-core hardware. The height 145 8 Part C (5 points) This problem continues to refer to the graph on the previous page. To be weakly scalable, a program must consist of two parts: • A part that is inherently sequential and can never be parallelized • A part that is parallelizable and will exhibit linear speedup in the number of threads Assume that facesim is weakly scalab...
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