On the Complexity of the Bernstein Combinatorial Problem

Every multivariate polynomial p(x), x = (x1, . . . , xn) ∈ [0, 1], is enclosed in the interval given by the smallest and the greatest of its coefficients in the Tensorial Bernstein Basis (TBB). Knowing that the total number of these TBB coefficients is exponential with respect to the number of variables n, ∏n i=1(1 + di), even if all partial degrees di equal 1, a combinatorial problem arises: is it possible to compute in polynomial time the smallest and the greatest coefficients? This article proves that the 3-SAT problem, known to be NP-complete, polynomially reduces to the above defined combinatorial problem, which let us consequently conclude that this problem is NP-hard.