1. An apparatus, comprising: a simulator that includes one or more computing circuits and that is configured to simulate a system and to propagate at least one state of the simulated system through time in response to a value of a parameter; a generator configured to generate a representation of a region of a plot having dimensions that respectively correspond at least to the parameter and to a characteristic of another state of the simulated system, the representation of the region including a representation of a multi-point first subregion of the plot, the first subregion spanning a multi-value range of the characteristic, and a representation of a second subregion of the plot in which a rate of change in the characteristic relative to the parameter has a magnitude that is greater than a first threshold; and a determiner configured to determine a next value of the parameter in response to the representation of the second subregion.