Leonidas Fegaras | Searcharxiv

arXiv2020

Translation of Array-Based Loops to Distributed Data-Parallel Programs

Large volumes of data generated by scientific experiments and simulations come in the form of arrays, while programs that analyze these data are frequently expressed in terms of array operations in an imperative, loop-based language. But, as datasets grow larger, new frameworks in distributed Big Data analytics have become essential tools to large-scale scientific computing. Scientists, who are typically comfortable with numerical analysis tools but are not familiar with the intricacies of Big Data analytics, must now learn to convert their loop-based programs to distributed data-parallel programs. We present a novel framework for translating programs expressed as array-based loops to distributed data parallel programs that is more general and efficient than related work. Although our translations are over sparse arrays, we extend our framework to handle packed arrays, such as tiled matrices, without sacrificing performance. We report on a prototype implementation on top of Spark and evaluate the performance of our system relative to hand-written programs.

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arXiv2016

Incremental Query Processing on Big Data Streams

This paper addresses online query processing for large-scale, incremental data analysis on a distributed stream processing engine (DSPE). Our goal is to convert any SQL-like query to an incremental DSPE program automatically. In contrast to other approaches, we derive incremental programs that return accurate results, not approximate answers. This is accomplished by retaining a minimal state during the query evaluation lifetime and by using incremental evaluation techniques to return an accurate snapshot answer at each time interval that depends on the current state and the latest batches of data. Our methods can handle many forms of queries on nested data collections, including iterative and nested queries, group-by with aggregation, and equi-joins. Finally, we report on a prototype implementation of our framework, called MRQL Streaming, running on top of Spark and we experimentally validate the effectiveness of our methods.

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