1. A computer-based method of debugging a debuggee computer program after an execution of at least a portion of the debuggee program, comprising: a) receiving a call graph having a plurality of nodes, each node representing a corresponding event that occurred during the debuggee program execution, the nodes ordered based on the debuggee program execution, including a first node representing a first event corresponding to a first machine address and corresponding to a source language statement and a second node representing a second event corresponding to a second machine address and corresponding to the source language statement; b) selectively clustering together the first node and the second node based on a comparison of the first machine address and the second machine address; and c) in response to a command to perform a step operation, selectively performing the step operation to include the first node and the second node, based on whether the first node and the second node are clustered.