1. A method of simulating a logic design, the method comprising: storing a first state to identify in a simulation of a logic design whether a node included in the logic design has a logic high value; storing a second state to identify in simulation of the logic design whether the node has a logic low value; storing a third state to identify in simulation of the logic design whether the node has an undefined state; and determining an output of the node in simulation of the logic design based on the first state, the second state, and the third state.