1. A method for functional verification of a design, comprising the steps of: identifying a feasible space of initial state vectors that can enable generation of stimuli for said design; sampling said feasible space to obtain a sample pool of initial state vectors; generating test stimuli to stimulate said design using respective members of said sample pool; evaluating results of an application of said test stimuli; responsively to said step of evaluating, establishing a subspace of said feasible space, said subspace comprising favorable initial state vectors; and selecting new initial state vectors from said subspace for use in generating functional tests for said design.