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Consider the polynomial algebra $\mathbb C[X]$. Then the set $\{1, X, X^2,\dots,\}$ forms a vector space basis for this algebra. In general, we know that the set $\{P_n(X) \in \mathbb C[X]: n \ge 0 \text{ and degree}(P_n) = n\}$ forms a basis. We consider the binomial basis defined as follows: $\binom{X}{n} = \frac{(X-n+1)(X-n+2)\cdots (X)}{1 \cdot 2 \cdot \, \cdots \, \cdot n }$. Then $\binom{X}{n}$ is a polynomial of degree $n$. Therefore $\{\binom{X}{n}: n \ge 0\}$ is yet another basis for $\mathbb C[X]$. I have the following questions.

  1. Is there any instance where the binomial basis is preferred over the usual basis?
  2. Is there any algorithms to switch between the usual and binomial basis?
  3. Is there any paper where they talk about the computation complexity of converting a polynomial expanded in binomial basis to the usual basis? Kindly share some references.

I have Theorem 1 and 2. Theorem 1 gives an expression for a polynomial in the usual basis and Theorem 2 gives an expression for the same polynomial in the binomial basis. I have to justify Theorem 1 is computationally preferred to calculate the polynomial over Theorem 2. But I am not sure how to approach this.

Thank you for your valuable time.

GA316
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  • The answer to Q2 is yes and algorithms are straightforward; I'd imagine you should be able to come up with them yourself. If you can't, what have you tried? For Q3, what is the fastest algorthm you've been able to find, and how does it work? – D.W. Oct 07 '20 at 06:05
  • Cross-posted: https://mathoverflow.net/q/373467/37212, https://cs.stackexchange.com/q/130911/755. Please do not post the same question on multiple sites. – D.W. Oct 07 '20 at 06:06
  • @D.W. Sorry. I have deleted the question in MO. – GA316 Oct 07 '20 at 06:17
  • @D.W. Can you please explain about the fastest algorithm that you are referring to? I haven't come across any such one. Thank you. – GA316 Oct 07 '20 at 06:23
  • I mean what is the best algorithm you can find? Can you find any correct algorithm at all? (even if it is slow?) What approaches have you considered? What prevents you from answering Q2 on your own? I hope you have tried to find an algorithm before asking here. We expect you to try to solve the problem on your own before asking here, and to show us your progress. – D.W. Oct 07 '20 at 06:55
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    This basis, also known as the Newton basis, is useful for constructing tree codes: https://eccc.weizmann.ac.il/report/2018/032/ – Yuval Filmus Oct 07 '20 at 09:50

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