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| Content Provider | Springer Nature Link |
|---|---|
| Author | Reichel, L. Plemmons, R. Sgallari, F. Morigi, S. |
| Copyright Year | 2010 |
| Abstract | Many questions in science and engineering give rise to linear ill-posed problems, whose solution is known to satisfy box constraints, such as nonnegativity. The solution of discretized versions of these problems is highly sensitive to perturbations in the data, discretization errors, and round-off errors introduced during the computations. It is therefore often beneficial to impose known constraints during the solution process. This paper describes a two-phase algorithm for the solution of large-scale box-constrained linear discrete ill-posed problems. The first phase applies a cascadic multilevel method and imposes the constraints on each level by orthogonal projection. The second phase improves the computed approximate solution on the finest level by an active set method. The latter allows several indices of the active set to be updated simultaneously. This reduces the computational effort significantly, when compared to standard active set methods that update one index at a time. Applications to image restoration are presented. |
| Ending Page | 105 |
| Page Count | 17 |
| Starting Page | 89 |
| File Format | |
| ISSN | 00080624 |
| e-ISSN | 11265434 |
| Journal | CALCOLO |
| Issue Number | 1 |
| Volume Number | 48 |
| Language | English |
| Publisher | Springer Milan |
| Publisher Date | 2010-09-21 |
| Publisher Place | Milan |
| Access Restriction | One Nation One Subscription (ONOS) |
| Subject Keyword | Optimization and variational techniques Multilevel method Iterative methods for linear systems Numerical Analysis Nonnegativity Theory of Computation Active set method Image restoration Improperly posed problems; regularization Constrained ill-posed problems |
| Content Type | Text |
| Resource Type | Article |
| Subject | Algebra and Number Theory Computational Mathematics |
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