On Diagonally Relaxed Orthogonal Projection Methods

Abstract. We propose and study a block-iterative projections method for solving linear equations and/or inequalities. The method allows diagonal component-wise relaxation in conjunction with orthogonal projections onto the individual hyperplanes of the system, and is thus called diagonallyrelaxed orthogonal projections (DROP). Diagonal relaxation has proven useful in accelerating the initial convergence of simultaneous and block-iterative projection algorithms but until now it was available only in conjunction with generalized oblique projections in which there is a special relation between the weighting and the oblique projections. DROP has been used by practitioners and in this paper a contribution to its convergence theory is provided. The mathematical analysis is complemented by some experiments in image reconstruction from projections which illustrate the performance of DROP. Key words. block-iterations, convex feasibility, diagonal relaxation, projection methods, simultaneous alg...

• Type: Journal
• Year: 2008
• Where: SIAMSC
• Authors: Yair Censor, Tommy Elfving, Gabor T. Herman, Touraj Nikazad
• Keywords: Block-iterative Projection, Oblique Projections, Orthogonal Projections, SIAMSC 2008