Two-loop five-point integration-by-parts relations in a usable form.

In this paper, we show that with the state-of-art module intersection IBP reduction method and our improved Leinartas' algorithm, IBP relations for very complicated Feynman integrals can be solved and the analytic reduction coefficients can be dramatically simplified. We develop a large scale parallel implementation of our improved Leinartas' algorithm, based on the \textsc{Singular}/\textsc{GPI-Space} framework. We demonstrate our method by the reduction of two-loop five-point Feynman integrals with degree-five numerators, with a simple and sparse IBP system. The analytic reduction result is then greatly simplified by our improved Leinartas' algorithm to a usable form, with a compression ratio of two order of magnitudes. We further discover that the compression ratio increases with the complexity of the Feynman integrals.