A computer-implemented method of determining an allocation plan for a cargo stowage problem of allocating a set of cargo items to a set of cargo item positions of a vessel, each cargo item position being suitable for receiving a cargo item. The method comprises constructing an expression indicative of one or more constraints to be satisfied by said allocation plan, constructing a cost function indicative of a cost of an updated allocation plan relative to a current allocation plan of said cargo stowage problem, iteratively updating a current allocation plan from an initial allocation plan to an updated allocation plan so as to decrease said cost function under said one or more constraints.