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time.pl
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time.pl
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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Written 2020-2024 by Markus Triska ([email protected])
Part of Scryer Prolog.
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/** This library provides predicates for reasoning about time.
*/
:- module(time, [max_sleep_time/1,
sleep/1,
time/1,
current_time/1,
format_time//2,
statistics/2
]).
:- use_module(library(format)).
:- use_module(library(iso_ext)).
:- use_module(library(error)).
:- use_module(library(dcgs)).
:- use_module(library(lists)).
:- use_module(library(charsio), [read_from_chars/2]).
%% current_time(-T)
%
% Yields the current system time _T_ in an opaque form, called a
% _time stamp_. Use `format_time//2` to describe strings that contain
% attributes of the time stamp.
current_time(T) :-
'$current_time'(T0),
read_from_chars(T0, T).
%% format_time(FormatString, TimeStamp)//
%
% The nonterminal format_time//2 describes a list of characters that
% are formatted according to a format string. Usage:
%
% ```
% phrase(format_time(FormatString, TimeStamp), Cs)
% ```
%
% TimeStamp represents a moment in time in an opaque form, as for
% example obtained by `current_time/1`.
%
% FormatString is a list of characters that are interpreted literally,
% except for the following specifiers (and possibly more in the future):
%
% | `%Y` | year of the time stamp. Example: 2020. |
% | `%m` | month number (01-12), zero-padded to 2 digits |
% | `%d` | day number (01-31), zero-padded to 2 digits |
% | `%H` | hour number (00-24), zero-padded to 2 digits |
% | `%M` | minute number (00-59), zero-padded to 2 digits |
% | `%S` | second number (00-60), zero-padded to 2 digits |
% | `%b` | abbreviated month name, always 3 letters |
% | `%a` | abbreviated weekday name, always 3 letters |
% | `%A` | full weekday name |
% | `%j` | day of the year (001-366), zero-padded to 3 digits |
% | `%%` | the literal `%` |
%
% Example:
%
% ```
% ?- current_time(T), phrase(format_time("%d.%m.%Y (%H:%M:%S)", T), Cs).
% T = [...], Cs = "11.06.2020 (00:24:32)".
% ```
format_time([], _) --> [].
format_time(['%','%'|Fs], T) --> !, "%", format_time(Fs, T).
format_time(['%',Spec|Fs], T) --> !,
( { member(Spec=Value, T) } ->
seq(Value)
; { domain_error(time_specifier, Spec, format_time//2) }
),
format_time(Fs, T).
format_time([F|Fs], T) --> [F], format_time(Fs, T).
%% max_sleep_time(T)
%
% The maximum admissible time span for `sleep/1`.
max_sleep_time(0xfffffffffffffbff).
%% sleep(S)
%
% Sleeps for S seconds (a floating point number or integer).
sleep(T) :-
builtins:must_be_number(T, sleep),
( T < 0 ->
domain_error(not_less_than_zero, T, sleep/1)
; max_sleep_time(N), T > N ->
throw(error(representation_error(max_sleep_time), sleep/1))
; '$sleep'(T)
).
%% statistics(?Keyword, ?List)
%
% Preliminary support for statistics/2, yielding timing information.
% The only supported `Keyword` is `runtime`. The first element of
% `List` is the CPU time in milliseconds, the second element is
% currently not supported.
statistics(runtime, [T,unsupported]) :-
'$cpu_now'(T0),
T is T0*1000.
:- meta_predicate time(0).
:- dynamic(time_id/1).
:- dynamic(time_state/3).
time_next_id(N) :-
( retract(time_id(N0)) ->
N is N0 + 1
; N = 0
),
asserta(time_id(N)).
%% time(Goal)
%
% Reports the execution time of Goal.
time(Goal) :-
cputime_inferences(T0, I0),
time_next_id(ID),
setup_call_cleanup(asserta(time_state(ID, T0, I0)),
( call_cleanup(catch(Goal, E, (report_time(ID),throw(E))),
Det = true),
time_true(ID),
( Det == true -> !
; true
)
; report_time(ID),
false
),
retract(time_state(ID, _, _))).
cputime_inferences(T, I) :-
'$cpu_now'(T),
'$inference_count'(I).
time_true(ID) :-
report_time(ID).
time_true(ID) :-
% on backtracking, update the stored CPU time for this ID
retract(time_state(ID, _, _)),
cputime_inferences(T0, I0),
asserta(time_state(ID, T0, I0)),
false.
report_time(ID) :-
time_state(ID, T0, I0),
cputime_inferences(T, I),
Time is T - T0,
Inferences0 is I - I0,
% we must subtract the number of inferences that time/1 itself takes;
% this may have to be adapted if the implementation changes,
% so that (for example) true/1 takes exactly 1 inference.
( bb_get('$answer_count', 0) ->
Inferences is Inferences0 - 60,
Pre = " ", Post = ""
; Inferences is Inferences0 - 9,
Pre = "", Post = " "
),
phrase((Pre,"% CPU time: ", format_("~3f", [Time]), "s, ",
format_("~U", [Inferences])," inference",s_if_necessary(Inferences),"\n",
Post), Cs),
format("~s", [Cs]).
s_if_necessary(Inferences) -->
{ compare(C, 1, Inferences) },
s_(C).
s_(=) --> "".
s_(<) --> "s".
s_(>) --> " (exception?)".
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
?- time((true;false)).
% CPU time: 0.000s, 1 inference
true
; % CPU time: 0.000s, 0 inference (exception?)
false.
:- time(use_module(library(clpz))).
% CPU time: 0.343s, 409_874 inferences
true.
:- time(use_module(library(lists))).
% CPU time: 0.000s, 19 inferences
true.
?- time(member(X, "abc")).
% CPU time: 0.000s, 1 inference
X = a
; % CPU time: 0.000s, 3 inferences
X = b
; % CPU time: 0.000s, 3 inferences
X = c.
?- time((repeat,false)).
% CPU time: 2.726s, 53_330_502 inferences
error('$interrupt_thrown',repl/0).
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