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 first state of the simulated system through time in response to a value of a first parameter; a generator configured to generate a representation of a region of a first plot having dimensions that respectively correspond at least to the parameter and to a characteristic of a second state of the simulated system, the representation of the region including a representation of a multi-point first subregion of the first plot, the first subregion spanning a first multi-value range of the characteristic, and a representation of a second subregion of the first 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 representation of a region of a second plot having dimensions that respectively correspond at least to the parameter and to a characteristic of a third state of the simulated system; and a determiner configured to determine a next value of the parameter in response to the representations of the second subregion of the first plot and the region of the second plot.