A method, according to an embodiment, provides a simulation of a physical real-world system, by first generating a system of equations that includes a discrete representation of the real-world system being simulated. Next, the real-world system is simulated. In simulating the system, a user specified tolerance of a solution of the system of equations is obtained. Then, the system of equations is iteratively solved until a solution to the system of equations for a given iteration is within the user specified tolerance of the solution of the system of equations for approximately infinite iterations. In such an embodiment, the solution to the system of equations for the given iteration is determined to be within the user specified tolerance using an experimentally determined constant, an estimate of a minimum eigenvalue of the system of equations for the given iteration, and a residual of the system of equations for the given iteration.