The formulas used in analytical methods to find numeric results are typically simple and convenient, making it possible to find exact results. If a system is complex, the resulting formulas may become complex, making the computational process lengthy and the results prone to round-off errors. In such circumstances, results may not be exact.

In general, computing results using explicit closed-form expressions is inefficient for complex systems because of long computation times and results with possible round-off errors. To improve computations, researchers have proposed several algorithms to calculate results more quickly and accurately. Advanced algorithms, such as the Pivotal decomposition method, are used when applicable.

Finding an exact analytical expression or algorithm for every scenario is difficult, especially when complex dependencies exist. Such dependencies might include warm standby components, shared repair resources, repair actions based on system state, imperfect maintenance actions, priorities in selecting paths in a network, and general failure/repair distributions. In such cases, simulation is typically used.