In granular physics, numerical simulations are often used to better explain the link between microscopic interaction mechanisms (e.g. contact forces between beads) and macroscopic laws (e.g. the maximum load at the bottom of a silo). Here we study the mechanical properties of a pile such that all the grains are in a static equilibrium. This paper presents a multi-agent approach that solves this problem. The main idea of this algorithm is to consider a grain as a reactive agent which goal is to reach its own static equilibrium. This algorithm can compute piles in practice in a complexity that is linear with respect to the number of grains. The performance of our algorithm has paved the way for the development of GranuLab, a virtual laboratory for scientific experiments in the domain of granular physics. We present both the algorithm and our validation processes.