Example of the importance in step error checking to reaction network integration. For Wagoner’s method (dashed line red), the algorithm can step past profile changes and therefore incorrectly compute nucleosynthesis activity while retaining good conservation of mass (the main tool available for estimating accuracy). Gear’s method (dot-dashed green line), on the other hand, can detect these changes by calculating the truncation error of each step, and return for smaller steps in the case where convergence fails. The solid, black line represents a Wagoner’s method calculation using conservative integration parameters found to produce converged nucleosynthesis results.