15. A computer-readable storage memory comprising computer program instructions for debugging a debuggee computer program based on a plurality of logged call trace events that result from an execution of at least a portion of the debuggee program, the program instructions executable by a processor to perform actions including: a) receiving an ordered set of the logged call trace events; b) determining whether to cluster together a subset of the set of the logged call trace events based on a machine address and a corresponding source language statement of each call trace event, the subset including at least two call trace events; and c) performing a step operation that includes the subset of logged call trace events based on the determining whether to cluster together the subset.
15. A computer-readable storage memory comprising computer program instructions for debugging a debuggee computer program based on a plurality of logged call trace events that result from an execution of at least a portion of the debuggee program, the program instructions executable by a processor to perform actions including: a) receiving an ordered set of the logged call trace events; b) determining whether to cluster together a subset of the set of the logged call trace events based on a machine address and a corresponding source language statement of each call trace event, the subset including at least two call trace events; and c) performing a step operation that includes the subset of logged call trace events based on the determining whether to cluster together the subset. 17. The computer-readable storage memory of claim 15 , determining whether to cluster comprises if the ordering of the subset of the logged call trace events is reversed to an ordering of the respective machine address of each call trace event, determining to not cluster together the subset of the logged call trace events.