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library(statistics): Get information about resource usage

A.49 library(statistics): 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.

[det]statistics
Print information about resource usage using print_message/2.
See also
All statistics printed are obtained through statistics/2.
[det]statistics(-Stats:dict)
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.
[nondet]thread_statistics(?Thread, -Stats:dict)
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.
[nondet]time(:Goal)
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.
bug
Inference statistics are often a few off.
call_time(:Goal, -Time:dict)
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.
profile(:Goal)
profile(:Goal, +Options)
Run Goal under the execution profiler. Defined options are:
time(Which)
Profile cpu or wall time. The default is CPU time.
top(N)
When generating a textual report, show the top N predicates.
cumulative(Bool)
If true (default false), show cumulative output in a textual report.
show_profile(+Options)
Display last collected profiling data. Options are
top(N)
When generating a textual report, show the top N predicates.
cumulative(Bool)
If true (default false), show cumulative output in a textual report.
[det]profile_data(-Data)
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:
summary:Dict
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.
nodes
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)
[nondet]profile_procedure_data(?Pred, -Data:dict)
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.

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LogicalCaptain said (2021-04-30T10:43:47):0 upvotes 0 0 downvotes
Picture of user LogicalCaptain.

There is some functionality for statistics which is hard to find in the manual.

This chapter, Obtaining Runtime Statistics, lists the following predicates:

The fact that the predicates are part of library(statistics) is shown in the header of the page, but the corresponding link directs back to Obtaining Runtime Statistics, not to library(statistics)

library(statistics) does not show up in the search bar, but can be found as:

library(statistics).

The lead-in text says:

The predicates of this library are for human use at the toplevel: information is printed.

It provides the following, two of which are listed above

The chapter, Execution Profiling is separate and lists further predicates provided by library(statistics):