  We develop a numerical method to compute the probabilities of multiparticle
production in weakly coupled scalar theories. Our technique is based on D.T.
Son's semiclassical method of singular solutions. Applying it to the process $1
\to n$ in the unbroken four-dimensional $\lambda\phi^4$ theory, we reproduce
the known results at ${1 \ll n \ll \lambda^{-1}}$.
