From: Walter Roberson <>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Polynomial roots
Date: Thu, 29 Apr 2010 16:29:11 -0500
Organization: The University of Manitoba
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Mark wrote:
> I'm trying to find the roots of 100 random polynomials of degree 5 and I 
> need help with finding the roots. I know that I can gernerate 100 
> polynomials by using
>                                          >> x=rand([100 6])
> I know that I can't do                                          >> roots(x)
> because the the input must be a vector. Is there anyway to to find all 
> the roots of 100 random polynomials without generating each polynomial 
> one by one.

Not for degree 5. For degree 4, there would be exact solutions you could 
plug the coefficients into, but for degree 5 unless you are lucky enough 
to be able to factorize, you need to use something like a binary search 
for sign changes over a hypothesized interval.

I'm not saying that it would not be possible to build a routine that did 
this kind of search in parallel, but it isn't the way the built-in 
routines are set up.