Compiling programs for profiling

To make use of the cost centre profiling system all modules must be compiled and linked with the `-prof' option. Any `_scc_' constructs you've put in your source will spring to life.

Without a `-prof' option, your `_scc_'s are ignored; so you can compiled `_scc_'-laden code without changing it.

There are a few other profiling-related compilation options. Use them in addition to `-prof'. These do not have to be used consistently for all modules in a program.

`-auto':

GHC will automatically add `_scc_' constructs for all top-level, exported functions.

`-auto-all':

All top-level functions, exported or not, will be automatically `_scc_''d.

`-caf-all':

The costs of all CAFs in a module are usually attributed to one "big" CAF cost-centre. With this option, all CAFs get their own cost-centre. An "if all else fails" option...

`-ignore-scc':

Ignore any `_scc_' constructs, so a module which already has `_scc_'s can be compiled for profiling with the annotations ignored.

`-G<group>':

Specifies the <group> to be attached to all the cost-centres declared in the module. If no group is specified it defaults to the module name.

In addition to the `-prof' option your system might be setup to enable you to compile and link with the `-prof-details' option instead. This enables additional detailed counts to be reported with the `-P' RTS option.