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ports.lgt source file defines a simple predicate execution box model
port profiler tool (inspired by the ECLiPSe
port_profiler tool). The box
model is the same used in the debugger tool.
The Logtalk predicate execution box model is an extended version of the
original Byrd's four port model. Besides the standard
redo ports, Logtalk also defines two (post-)unification ports,
rule, and an
exception port. This tool counts and reports the
number of times each port is traversed during the execution of queries.
It also distinguishes between deterministic exits (reported in the
column in the profiling result tables) and exits that leave choice-points
(reported in the
To consult this tool API documentation, open in a web browser the link:
For sample queries, please see the SCRIPT.txt file.
| ?- logtalk_load(ports(loader)).
Note that this tool cannot be loaded at the same time as other tools (e.g. the debugger) that also provide a debug handler, which must be unique in a running session.
Compiling source files for port profiling
To compile source files for port profiling, simply compile them in debug mode
and with the
source_data flag turned on. For example:
| ?- logtalk_load(my_source_file, [debug(on), source_data(on)]).
Alternatively, you can also simply turn on the
globally before compiling your source files:
| ?- set_logtalk_flag(debug, on), set_logtalk_flag(source_data, on).
Be aware, however, that loader files (e.g. library loader files) may override default flag values and thus loaded files may not be compiled in debug mode.
Generating profiling data
After loading this tool and compiling the source files that you want to profile in debug mode, simply call the goals to be profiled.
Printing profiling data reports
After calling the goals that you want to profile, you can print a table with all profile data by typing:
| ?- ports::data.
To print a table with data for a single entity, use the query:
| ?- ports::data(Entity).
The profiling data can be reset using the query:
| ?- ports::reset.
To reset only the data about a specific entity, use the query:
| ?- ports::reset(Entity).
Interpreting profiling data
Some useful information that can be inferred from the profiling data include:
- which predicates are called more often (from the
- unexpected failures (from the
- unwanted non-determinism (from the
- performance issues due to backtracking (from the
- predicates acting like a generator of possible solutions (from the
- inefficient indexing of predicate clauses (from the
The profiling data should be analyzed taking into account the expected behavior for the profiled predicates.
Determinism information is currently not available when using Lean Prolog or Quintus Prolog as backend compilers.
All source files are formatted using tabs (the recommended setting is a tab width equivalent to 4 spaces).