To generate a time and allocation profile, give one of the
following RTS options to the compiled program when you run it (RTS
options should be enclosed between +RTS...-RTS
as usual):
-p or -P or -pa:
The -p option produces a standard
time profile report. It is written
into the file
program.prof
The -P option produces a more
detailed report containing the actual time and allocation
data as well. (Not used much.)
The -pa option produces the most detailed
report containing all cost centres in addition to the actual time
and allocation data.
-Vsecs
Sets the interval that the RTS clock ticks at, which is also the sampling interval of the time and allocation profile. The default is 0.02 seconds.
-xc
This option causes the runtime to print out the
current cost-centre stack whenever an exception is raised.
This can be particularly useful for debugging the location
of exceptions, such as the notorious Prelude.head:
empty list error. See Section 4.17.7, “RTS options for hackers, debuggers, and over-interested
souls”.