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This file is part of Logtalk
Copyright 1998-2018 Paulo Moura

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.


This tool contains simple wrappers for selected Prolog profiler tools.


This tool can be loaded using the query:

| ?- logtalk_load(assertions(loader)).

For sample queries, please see the SCRIPT.txt file.

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) by typing:

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

Given that prolog_statistics:profile/1 is a meta-predicate, Logtalk will compile its argument before calling it. Don't forget, however, to load the prolog_statistics module before using or compiling calls to the profile/1 predicate by typing:

| ?- use_module(library(statistics)).

The profiler support makes no attempt to conceal the internal Logtalk compiler/runtime predicates or the generated 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 be listed when your code uses dynamic binding.

Compiling source code for profiling

In order to get user-level object and predicate names instead of compiler generated names when using the SWI-Prolog and YAP profilers you must set code_prefix flag to a value other than the default $. For example:

| ?- set_logtalk_flag(code_prefix, '.').

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

Other notes

All source files are formatted using tabs (the recommended setting is a tab width equivalent to 4 spaces).