All predicatesShow -- Get information about resource usage

This library provides predicates to obtain information about resource usage by your program. The predicates of this library are for human use at the toplevel: information is printed. All predicates obtain their information using public low-level primitives. These primitives can be use to obtain selective statistics during execution.

Source statistics is det
Print information about resource usage using print_message/2.
See also
- All statistics printed are obtained through statistics/2.
Source statistics(-Stats:dict) is det
Stats is a dict representing the same information as statistics/0. This convience function is primarily intended to pass statistical information to e.g., a web client. Time critical code that wishes to collect statistics typically only need a small subset and should use statistics/2 to obtain exactly the data they need.
Source thread_statistics(?Thread, -Stats:dict) is nondet
Obtain statistical information about a single thread. Fails silently of the Thread is no longer alive.
Stats- is a dict containing status, time and stack-size information about Thread.
Source time(:Goal) is nondet
Execute Goal, reporting statistics to the user. If Goal succeeds non-deterministically, retrying reports the statistics for providing the next answer.

Statistics are retrieved using thread_statistics/3 on the calling thread. Note that not all systems support thread-specific CPU time. Notable, this is lacking on MacOS X.

See also
- statistics/2 for obtaining statistics in your program and understanding the reported values.
- call_time/2, call_time/3 to obtain the timing in a dict.
- Inference statistics are often a few off.
Source call_time(:Goal, -Time:dict)
Source call_time(:Goal, -Time:dict, -Result)
Call Goal as call/1, unifying Time with a dict that provides information on the resource usage. Currently Time contains the keys below. Future versions may provide additional keys.
  • wall:Seconds
  • cpu:Seconds
  • inferences:Count
Result- is one of true or false depending on whether or not the goal succeeded.
Source profile(:Goal)
Source profile(:Goal, +Options)
Run Goal under the execution profiler. Defined options are:
Profile cpu or wall time. The default is CPU time.
When generating a textual report, show the top N predicates.
If true (default false), show cumulative output in a textual report.
Source show_profile(+Options)
Display last collected profiling data. Options are
When generating a textual report, show the top N predicates.
If true (default false), show cumulative output in a textual report.
Source profile_data(-Data) is det
Gather all relevant data from profiler. This predicate may be called while profiling is active in which case it is suspended while collecting the data. Data is a dict providing the following fields:
Overall statistics providing
  • samples:Count: Times the statistical profiler was called
  • ticks:Count Virtual ticks during profiling
  • accounting:Count Tick spent on accounting
  • time:Seconds Total time sampled
  • nodes:Count Nodes in the call graph.
List of nodes. Each node provides:
  • predicate:PredicateIndicator
  • ticks_self:Count
  • ticks_siblings:Count
  • call:Count
  • redo:Count
  • exit:Count
  • callers:list_of(Relative)
  • callees:list_of(Relative)

Relative is a term of the shape below that represents a caller or callee. Future versions are likely to use a dict instead.

node(PredicateIndicator, CycleID, Ticks, TicksSiblings,
     Calls, Redos, Exits)
Source prof_statistics(-Node) is det[private]
Get overall statistics
Node- term of the format prof(Ticks, Account, Time, Nodes)
Source profile_procedure_data(?Pred, -Data:dict) is nondet
Collect data for Pred. If Pred is unbound data for each predicate that has profile data available is returned. Data is described in profile_data/1 as an element of the nodes key.
Source value(+Key, +NodeData, -Value)[private]
Obtain possible computed attributes from NodeData.

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

Source profile(Arg1, Arg2)
Source call_time(Arg1, Arg2, Arg3)