TCSlib

1 This is a Test

In this chapter, this is a test.

Lemma 1.1 Welch-Berlekamp Algorithm
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If there is a polynomial \(f\) with degree at most \(k-1\) such that \(\Delta (f,w)\leq e\), then there exists \(E\) and \(Q\) satisfying:

  • \(\textrm{deg}(E(X))=e\) and \(E(X)\) is monic.

  • \(\textrm{deg}(Q(X))\leq e+k-1\).

  • \(w_i\cdot E(\alpha _i)=Q(\alpha _i)\) for all \(i=1,...,n\).

Proof

Consider the error-locator polynomial of the form

\[ E(X)=\Pi _{i: f(a_i)\neq y_i}(x-a_i). \]
Lemma 1.2 Jensen
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If \(S\) is a finite set, and \(\sum _{s \in S} w_s = 1\) for some non-negative \(w_s\), and \(p_s \in [0,1]\) for all \(s \in S\), then

\[ \sum _{s \in S} w_s h(p_s) \leq h(\sum _{s \in S} w_s p_s). \]