  The importance of graph search algorithm choice to the directed relation
graph with error propagation (DRGEP) method is studied by comparing basic and
modified depth-first search, basic and R-value-based breadth-first search
(RBFS), and Dijkstra's algorithm. By using each algorithm with DRGEP to produce
skeletal mechanisms from a detailed mechanism for n-heptane with
randomly-shuffled species order, it is demonstrated that only Dijkstra's
algorithm and RBFS produce results independent of species order. In addition,
each algorithm is used with DRGEP to generate skeletal mechanisms for n-heptane
covering a comprehensive range of autoignition conditions for pressure,
temperature, and equivalence ratio. Dijkstra's algorithm combined with a
coefficient scaling approach is demonstrated to produce the most compact
skeletal mechanism with a similar performance compared to larger skeletal
mechanisms resulting from the other algorithms. The computational efficiency of
each algorithm is also compared by applying the DRGEP method with each search
algorithm on the large detailed mechanism for n-alkanes covering n-octane to
n-hexadecane with 2115 species and 8157 reactions. Dijkstra's algorithm
implemented with a binary heap priority queue is demonstrated as the most
efficient method, with a CPU cost two orders of magnitude less than the other
search algorithms.
