Gottfried Helms on Thu, 17 Nov 2022 19:31:22 +0100 |
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Re: Conversion of a function/closure with rational coefficients into one with real coefficients |
Am 17.11.2022 um 18:25 schrieb Bill Allombert: > On Thu, Nov 17, 2022 at 01:42:58PM +0100, Gottfried Helms wrote: >> I'm trying to optimize some bivariate function, >> and found, that I can create a vector of polynomials p_r(x). >> Let pp be a vector of closures, so for instance >> >> ... >> pp[4](x) = 1/4*x^2-2/3*x+1/6 >> pp[5](x) = -1/8*x^3+31/48*x^2-7/12*x+1/24 >> ... > > Why not write > > pp[4] = 1/4*x^2-2/3*x+1/6 > pp[5] = -1/8*x^3+31/48*x^2-7/12*x+1/24 > > and use subst to evaluate pp[i] when needed ? > > Cheers, > Bill > > The problem that I have is runtime-behave. pp[128] has order 126 polynomial with rational coefficients with hundred or more digits in numerator and denominator. Experiments with some manually generated real valued coefficients show much better runtime behave. I think it is better to have polynomials statically defined in the most appropriate form, so that any overload in typeconversion at runtime occurs only minimally. Gottfried