A Descartes Algorithms for Polynomials with Bit-Stream Coefficients
The Descartes method is an algorithm for isolating the
real roots of square-free polynomials with real coefficients. We assume
that coefficients are given as (potentially infinite) bit-streams. In other
words, coefficients can be approximated to any desired accuracy, but are not
known exactly. We show that
a variant of the Descartes algorithm can cope with bit-stream
coefficients. To isolate the real roots of a
square-free real polynomial $q(x) = q_nx^n+ldots+q_0$ with root
separation $
ho$, coefficients $abs{q_n}ge1$ and $abs{q_i} le 2^ au$,
it needs coefficient approximations to $O(n(log(1/
ho) + au))$
bits after the binary point and has an expected cost of
$O(n^4 (log(1/
ho) + au)^2)$ bit operations.
Root Isolation
Interval Arithmetic
Descartes Algorithm
1-12
Regular Paper
Kurt
Mehlhorn
Kurt Mehlhorn
Arno
Eigenwillig
Arno Eigenwillig
Lutz
Kettner
Lutz Kettner
Werner
Krandick
Werner Krandick
Susanne
Schmitt
Susanne Schmitt
Nicola
Wolpert
Nicola Wolpert
10.4230/DagSemProc.06021.3
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