1. A method for performing simulations through computer processes, the method comprising the steps of: observing measured values of an event to provide observed values, wherein said step of observing starts at a predetermined observation time; concurrently running a first plurality of simulations, wherein said first plurality of simulations have behaviors that are characterized by different parameters and start at said predetermined observation time; producing a discrete distribution at a predetermined time after said predetermined observation time, wherein said discrete distribution is based on distances between said measured values at the predetermined time and a value of each of the first plurality of simulations at the predetermined time; and selecting a second plurality of simulations from the first plurality of simulations based on said discrete distribution, wherein a probability of selecting one of the first plurality of simulations decreases as the difference between the measured values at the predetermined time and the value of the one of the first plurality of simulations at the predetermined time increases, wherein the second plurality of simulations is a subset of the first plurality of simulations.