Just checked on the 70000+ simulations I submitted to the Cow last night. The purpose of these runs is to explore a given system (the logistic growth model in this case) using different implementations of the stochastic simulation algorithm (aka SSA methods). In this batch of runs I am utilizing Gillespie’s Direct method, which is the exact implementation, and three tau-leap methods (Explicit tau-leap, Binomial tau-leap, and Optimized tau-leap), all which are approximate implementations of the SSA.

Here’s the status so far. All of the tau-leap methods have finished. The Explicit tau-leap method took 75 minutes to crunch through 10000 simulations, the Binomial tau-leap took 17 minutes, and the Optimized tau-leap took 121 minutes. Although there are substantial timing differences between the methods it all appears rather minute compared to the timings of the Direct method which still is working on it’s 10k runs (about 12 hours after starting). A simple extrapolation reveals an estimated wall time to completion of 119 days!!! I am (was) intending to have this manuscript submitted well before that. On the bright side though – at least the results will be *exact*!

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**Tags:** computer cluster, computer simulations, Gillespie algorithm, GillespieSSA, R