We present Hermite polynomial interpolation algorithms that for a sparse univariate polynomial with coefficients from a field compute the polynomial from fewer points than the classical algorithms. If the interpolating polynomial has terms, our algorithms, require argument/value triples ( , ( ), ′ ( )) for = 0, . . . , + ⌈( +1)/2⌉ −1, where is randomly sampled and the probability of a correct output is determined from a degree bound for . With ′ we denote the derivative of . Our algorithms generalize to multivariate polynomials, higher derivatives and sparsity with respect to Chebyshev polynomial bases. We have algorithms that can correct errors in the points by oversampling at a limited number of good values. If an upper bound ≥ for the number of terms is given, our algorithms use a randomly selected and, with high probability, ⌈ /2⌉ + triples, but then never return an incorrect output.The algorithms are based on Prony's sparse interpolation algorithm. While Prony's algorithm and its variants use fewer values, namely, 2 + 1 and + values ( ), respectively, they need more arguments . The situation mirrors that in algebraic error correcting codes, where the Reed-Solomon code requires fewer values than the multiplicity code, which is based on Hermite interpolation, but the Reed-Solomon code requires more distinct arguments. Our sparse Hermite interpolation algorithms can interpolate polynomials over finite fields and over the complex numbers, and from floating point data. Our Prony-based approach does not encounter the Birkhoff phenomenon of Hermite interpolation, when a gap in the derivative values causes multiple interpolants. We can interpolate from + 1 values of and 2 − 1 values of ′ .
CCS CONCEPTS• Mathematics of computing → Interpolation.