Sylvain Rubenthaler Optimal portfolio allocation strategy and optimal filter in a simple model : numerical issues Abstract : We are interested in a model of portfolio with one riskless asset and one risky asset whose drift is jumping between mu_1 and mu_2. The optimal portfolio is based of the conditional probability of the drift to be mu_1 knowing the prices of the assets. This conditional probability is the solution of an SDE which could be approximated by an Euler scheme. We propose another scheme, inspired by classical filtering theory, which is better in some sense. I must add that this is a work in progress and that the fact that our scheme is better is not yet established in a satisfactory way.