The block-wise circumcentered–reflection method


The elementary Euclidean concept of circumcenter has recently been employed to improve two aspects of the classical Douglas–Rachford method for projecting onto the intersection of affine subspaces. The so-called circumcentered–reflection method is able to both accelerate the average reflection scheme by the Douglas–Rachford method and cope with the intersection of more than two affine subspaces. We now introduce the technique of circumcentering in blocks, which, more than just an option over the basic algorithm of circumcenters, turns out to be an elegant manner of generalizing the method of alternating projections. Linear convergence for this novel block-wise circumcenter framework is derived and illustrated numerically. Furthermore, we prove that the original circumcentered–reflection method essentially finds the best approximation solution in one single step if the given affine subspaces are hyperplanes.

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We dedicate this paper in honor of the 70th birthday of Professor J. M. Martínez and of the 60th birthday of Professor Yuan Jinyun. The first author wants to thank the Federal University of Santa Catarina and remarks that part of his contribution to the present work was carried out at this institution. We thank the anonymous referees for their valuable suggestions which significantly improved the presentation of this manuscript.

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Correspondence to Roger Behling.

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RB was partially supported by Brazilian Agency Conselho Nacional de Pesquisa (CNPq), Grants 304392/2018-9 and 429915/2018-7; JYBC was partially supported by the National Science Foundation (NSF), Grant DMS—1816449.

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Behling, R., Bello-Cruz, J. & Santos, L. The block-wise circumcentered–reflection method. Comput Optim Appl 76, 675–699 (2020).

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  • Accelerating convergence
  • Best approximation problem
  • Circumcenter scheme
  • Douglas–Rachford method
  • Linear and finite convergence
  • Method of alternating projections

Mathematics Subject Classification

  • 49M27
  • 65K05
  • 65B99
  • 90C25