Before profiling an execution, the program must be compiled in profiling mode, using the ocamlcp front-end to the ocamlc compiler (see chapter 8). When compiling modules separately, ocamlcp must be used when compiling the modules (production of .cmo files), and can also be used (though this is not strictly necessary) when linking them together. Note
If a module (.ml file) doesn't have a corresponding interface (.mli file), then compiling it with ocamlcp will produce object files (.cmi and .cmo) that are not compatible with the ones produced by ocamlc, which may lead to problems (if the .cmi or .cmo is still around) when switching between profiling and non-profiling compilations. To avoid this problem, you should always have a .mli file for each .ml file. Note
To make sure your programs can be compiled in profiling mode, avoid using any identifier that begins with __ocaml_prof.
The amount of profiling information can be controlled through the -p option to ocamlcp, followed by one or several letters indicating which parts of the program should be profiled:
function calls : a count point is set at the beginning of function bodies
if ...then ...else ... : count points are set in both then branch and else branch
while, for loops: a count point is set at the beginning of the loop body
match branches: a count point is set at the beginning of the body of each branch
try ...with ... branches: a count point is set at the beginning of the body of each branch
For instance, compiling with ocamlcp -p film profiles function calls, if...then...else..., loops and pattern matching.
Calling ocamlcp without the -p option defaults to -p fm, meaning that only function calls and pattern matching are profiled.
Due to the implementation of streams and stream patterns as syntactic sugar, it is hard to predict what parts of stream expressions and patterns will be profiled by a given flag. To profile a program with streams, we recommend using ocamlcp -p a.