Abstract
In this note we compare the randomized extended Kaczmarz (EK) algorithm and randomized coordinate descent (CD) for solving the full-rank overdetermined linear least-squares problem and prove that CD needs fewer operations for satisfying the same residual-related termination criteria. For the general least-squares problems, we show that first running CD to compute the residual and then standard Kaczmarz on the resulting consistent system is more efficient than EK.
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Acknowledgments
The author is indebted to Liang Dai for stimulating discussions on the Kaczmarz algorithm and for pointing out [7] and to the reviewers for their constructive comments.
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Communicated by Rosemary Renaut.
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Dumitrescu, B. On the relation between the randomized extended Kaczmarz algorithm and coordinate descent. Bit Numer Math 55, 1005–1015 (2015). https://doi.org/10.1007/s10543-014-0526-9
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DOI: https://doi.org/10.1007/s10543-014-0526-9