  Today most developers utilize source code written by other parties. Because
the code is modified frequently, the developers need to grasp the impact of the
modification repeatedly. A call graph and especially its special type, a call
path, help the developers comprehend the modification. Source code written by
other parties, however, becomes too huge to be held in memory in the form of
parsed data for a call graph or path. This paper offers a bidirectional search
algorithm for a call graph of too huge amount of source code to store all parse
results of the code in memory. It refers to a method definition in source code
corresponding to the visited node in the call graph. The significant feature of
the algorithm is the referenced information is used not in order to select a
prioritized node to visit next but in order to select a node to postpone
visiting. It reduces path extraction time by 8% for a case in which ordinary
path search algorithms do not reduce the time.
