Intel® Trace Analyzer can display and analyze general (properly nested) state changes, relating to subroutine calls, entry/exit to/from code regions and other activities occurring in a process. Intel® Trace Analyzer implements a two-level model of states: a state is referred to by an activity name that identifies a group of states, and the state (or symbol) name that references a particular state in that group. For instance, all MPI routines are part of the activity MPI, and each one is identified by its routine name, for instance MPI_Send for C and for Fortran.
The Intel® Trace Collector API allows the user to define arbitrary activities and symbols and to record entry and exit to/from them. In order to reduce the instrumentation overhead, symbols are referred to by integer handles that can be managed automatically (using the VT_funcdef() interface) or assigned by the user (using the old VT_symdef() routine). All activities and symbols are defined by each process that uses them, but it is no longer necessary to define them consistently on all processes (see UNIFY-SYMBOLS).
Optionally, information about source locations can be recorded for state enter and exit events by passing a non-null location handle to the VT_enter()/VT_leave() or VT_beginl()/VT_endl() routines.