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Exact Algorithms for Complex Root Isolation

Supervisor

Suitable for

MSc in Computer Science
Computer Science and Philosophy, Part C
Computer Science, Part B
Mathematics and Computer Science, Part C
Computer Science, Part C

Abstract

Not available in 2013/14

Isolating the complex roots of a polynomial can be achieved using subdivision algorithms. Traditional Newton methods can be applied in conjunction with interval arithmetic. Previous work (jointly with Prof Chee Yap and MSc student Narayan Kamath) has compared the performance of three operators: Moore's, Krawczyk's and Hansen-Sengupta's. This work makes extensive use of the CORE library, which is is a collection of C++ classes for exact computation with algebraic real numbers and arbitrary precision arithmetic. CORE defines multiple levels of operation over which a program can be compiled and executed. Each of these levels provide stronger guarantees on exactness, traded against efficiency. Further extensions of this work can include (and are not limited to): (1) Extending the range of applicability of the algorithm at CORE's Level 1; (2) Making an automatic transition from CORE's Level 1 to the more detailed Level 2 when extra precision becomes necessary; (3) Designing efficiency optimisations to the current approach (such as confirming a single root or analysing areas potentially not containing a root with a view to discarding them earlier in the process); (4) Tackling the isolation problem using a continued fraction approach. The code has been included and is available within the CORE repository. Future work can continue to be carried out in consultation with Prof Yap at NYU.