MapReduce has emerged as a viable competitor to database systems in big data analytics. MapReduce programs are being written for a wide variety of application domains including business data processing, text analysis, natural language processing, Web graph and social network analysis, and computational science. However, MapReduce systems lack a feature that has been key to the historical success of database systems, namely, cost-based optimization. A major challenge here is that, to the MapReduce system, a program consists of black-box map and reduce functions written in some programming language like C++, Java, Python, or Ruby.
Starfish
is a self-tuning system for big data analytics that includes, to our knowledge, the first
Cost-based Optimizer
for simple to arbitrarily complex MapReduce programs. Starfish also includes a
Profiler
to collect detailed statistical information from unmodified MapReduce programs, and a
What-if Engine
for fine-grained cost estimation. This demonstration will present the profiling, what-if analysis, and cost-based optimization of MapReduce programs in Starfish. We will show how (nonexpert) users can employ the
Starfish Visualizer
to (a) get a deep understanding of a MapReduce program's behavior during execution, (b) ask hypothetical questions on how the program's behavior will change when parameter settings, cluster resources, or input data properties change, and (c) ultimately optimize the program.
This paper proposes a robust design for the ac/ac chopper-based voltage sag/swell compensation systems. This includes the design of a new buck-boost topology and the application of a robust switching scheme for a voltage compensator. The proposed circuit can operate in the buck or boost mode for both the sag and the swell compensations. A control scheme for a fast compensation is also proposed which is suitable for the ac/ac chopper-based compensation system. Detailed analysis and verification through a simulation in the MATLAB are presented highlighting the advantages of the proposed technique. An experimental verification has also been performed by using a laboratory prototype system.
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