1. Computer-readable media, which when read and executed by a computer employing an operating system enabling process forking, causes the computer to carry out a method for simulating behavior of an electronic circuit and then re-simulating behavior of at least a portion of the electronic circuit in response to an input re-simulation request, the method comprising the steps of: a. initiating a first simulation process for simulating the behavior of the electronic circuit; wherein the first simulation process forks at least one checkpoint to create a checkpoint process that is a copy of the first simulation process, and wherein the first simulation process simulates the behavior of the electronic circuit following each checkpoint; b. suspending each checkpoint process upon its creation; and c. responding to a first re-simulation request invoking a first checkpoint by resuming the checkpoint process that was created at the first checkpoint.