.. _library_profiler:

profiler

This tool contains simple wrappers for selected Prolog profiler tools.

Loading

This tool can be loaded using the query:

::

?- logtalk_load(profiler(loader)).

For sample queries, please see the SCRIPT.txt file in the tool directory.

Testing

To test this tool, load the tester.lgt file:

::

| ?- logtalk_load(profiler(tester)).

Supported backend Prolog compilers

Currently, this tool supports the profilers provided with SICStus Prolog 4, SWI-Prolog, and YAP. The tool includes two files:

• | yap_profiler.lgt | simple wrapper for the YAP count profiler
• | sicstus_profiler.lgt | simple wrapper for the SICStus Prolog 4 profiler

  Logtalk also supports the YAP tick profiler (using the latest YAP development version) and the SWI-Prolog XPCE profiler. When using the XPCE profiler, you can avoid profiling the Logtalk compiler (which is invoked, e.g., when you use the (::)/2 message-sending operator at the top-level interpreter) by compiling your code with the optimize flag turned on:

  ::

  ?- set_logtalk_flag(optimize, on). true.

  ?- use_module(library(statistics)). true.

  ?- profile(... :: ...). ...

  Given that is a meta-predicate, Logtalk will compile its argument before calling it thanks to the goal_expansion/2 hook predicate definitions in the adapter file. Without this hook definition, you would need to use instead (to avoid profiling the compiler itself):

  ::

  ?- logtalk << (prolog_statistics:profile(... :: ...)). ...

  In either case, don't forget, however, to load the prolog_statistics module before using or compiling calls to the profile/1 to allow the Logtalk compiler to access its meta-predicate template.

  The profiler support attempts to conceal internal Logtalk compiler/runtime predicates and the generated entity predicates that implement predicate inheritance. Calls to internal compiler and runtime predicates have functors starting with $lgt_. Calls to predicates with functors such as _def, _dcl, or _super, used to implement inheritance, may still be listed in a few cases. Note that the time and the number of calls/redos of concealed predicates are added to the caller predicates.

Compiling source code for profiling

To get the user-level object and predicate names instead of the compiler-generated internal names when using the SWI-Prolog and YAP profilers, you must set code_prefix flag to a character other than the default $ before compiling your source code. For example:

::

?- set_logtalk_flag(code_prefix, '.').

See also the settings-sample.lgt file for automating the necessary setup at Logtalk startup.