Ranged reactors are a new feature in RMG v3.0 to simplify the task of specifying a range of initial conditions. With the new feature, ranges for T, P, and X 0 can be directly specified for a single reactor block. Internally, RMG will automatically select points within the space of conditions for each iteration, using a weighted stochastic grid sampling algorithm. On each iteration, a coarse grid with 20 points in each dimension is constructed, and the desirability of each point is evaluated based on the number of iterations since it was last chosen. The desirability values are normalized to form probabilities, and a random point is chosen using those probabilities. The algorithm then takes a random step from the chosen point, with a maximum distance of √ 2/2 times the distance between grid points. That point is then used for the simulation. The algorithm continues iterating through the grid points considering the probabilities described above. A simplified example of the algorithm for two dimensions is shown in Figure .