DiFX2：一个更加灵活、高效、健壮和强大的软件关联函数
DiFX2: A more flexible, efficient, robust and powerful software correlator
摘要：
软件相关性，其中以诸如C++的高级语言编写的相关算法在商用计算机硬件上运行，对于小型到中型和/或带宽受限的无线电干涉仪已经变得越来越有吸引力。特别地，许多长基线阵列（其通常具有少于20个元件，并且在观察带宽方面受到昂贵的记录硬件和介质的限制）已经利用软件解调器来进行快速的、成本有效的关联函数升级，以允许与新的、更宽带宽的记录系统兼容，并且提高关联函数的灵活性。DiFX关联函数于2007年公开发布，一直是此类升级的热门选择，目前已被全球许多天文台和研究小组用于生产关联。在这里，我们描述了过去三年中DiFX关联函数功能的演变，包括许多新功能，实质性的性能改进，以及大量的支持基础设施，以简化代码的使用。新功能包括在单个相关通道中关联大量相位中心的能力、相位校准音的提取、不同但重叠的子带的相关、以最小成本快速采样滤波器组和峰度数据的产生等等。代码的最新版本比原始版本至少快15%，在某些情况下甚至快了很多倍。最后，我们还提出了详细的测试结果验证新代码的正确性。
英文摘要：
Software correlation, where a correlation algorithm written in a high-level language such as C++ is run on commodity computer hardware, has become increasingly attractive for small to medium sized and/or bandwidth constrained radio interferometers. In particular, many long baseline arrays (which typically have fewer than 20 elements and are restricted in observing bandwidth by costly recording hardware and media) have utilized software correlators for rapid, cost-effective correlator upgrades to allow compatibility with new, wider bandwidth recording systems and improve correlator flexibility. The DiFX correlator, made publicly available in 2007, has been a popular choice in such upgrades and is now used for production correlation by a number of observatories and research groups worldwide. Here we describe the evolution in the capabilities of the DiFX correlator over the past three years, including a number of new capabilities, substantial performance improvements, and a large amount of supporting infrastructure to ease use of the code. New capabilities include the ability to correlate a large number of phase centers in a single correlation pass, the extraction of phase calibration tones, correlation of disparate but overlapping sub-bands, the production of rapidly sampled filterbank and kurtosis data at minimal cost, and many more. The latest version of the code is at least 15% faster than the original, and in certain situations many times this value. Finally, we also present detailed test results validating the correctness of the new code.
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