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        <article-title>SABER: Window-Based Hybrid Stream Processing for Heterogeneous Architectures?</article-title>
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      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Alexandros Koliousis</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Matthias Weidlich</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Raul Castro Fernandez</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Alexander L. Wolf</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Paolo Costa]</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Peter Pietzuch</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>akolious</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>mweidlic</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>costa</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>prpg@imperial.ac.uk</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Imperial College London</string-name>
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      <abstract>
        <p>? Published as: A. Koliousis, M. Weidlich, R. C. Fernandez, A. L. Wolf, P. Costa, and P. Pietzuch. SABER: Window-based hybrid stream processing for heterogeneous architectures. In F. O¨zcan, G. Koutrika, and S. Madden, editors, Proceedings of the 2016 SIGMOD Conference, San Francisco, CA, USA, June 26 - July 01, 2016, pages 555-569, ACM.</p>
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      <p>‡Humboldt-Universita¨t zu Berlin
]Microsoft Research
Stream processing systems found wide-spread application in domains such as credit
fraud detection, urban traffic management, and click stream analytics. These systems
process continuous streams of input data in an online manner, aiming at maximising
processing throughput while staying within acceptable latency bounds. Heterogeneous
architectures that combine multi-core CPUs with many-core GPGPUs have the potential
to improve the performance of stream processing engines. Yet, a stream processing
engine must execute streaming SQL queries with sufficient data-parallelism to fully
utilise the available heterogeneous processors, and decide how to use each processor in
the most effective way.</p>
      <p>Addressing these challenges, we present SABER, a hybrid high-performance
relational stream processing engine for CPUs and GPGPUs. It executes window-based
streaming SQL queries following a hybrid execution model. Specifically, SABER
incorporates the following innovations:</p>
      <p>It features a hybrid stream processing model based on query tasks, each comprising a
batch of stream data and a query operator. Instead of relying on offline performance
models to select the processor on which to run a query operator, SABER employs an
adaptive heterogeneous lookahead scheduling strategy to balance the load on the
different types of processors.</p>
      <p>It provides window-aware task processing, supporting sliding window semantics
in the presence of fixed-sized batches. SABER ensures result correctness after the
out-of-order processing of tasks by first buffering and then incrementally releasing
the results as tasks finish execution.</p>
      <p>It exploits pipelined stream data movement to the GPGPU that interleaves data
movement and task execution, thereby maintaining high utilisation of the PCIe
bandwidth.</p>
      <p>An experimental comparison against state-of-the-art engines shows that SABER increases
processing throughput while maintaining low latency for a wide range of streaming SQL
queries with both small and large window sizes.</p>
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