172 lines
5.0 KiB
Prolog
172 lines
5.0 KiB
Prolog
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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Written 2020-2023 by Markus Triska (triska@metalevel.at)
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Part of Scryer Prolog.
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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/** This library provides predicates for reasoning about time.
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*/
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:- module(time, [max_sleep_time/1, sleep/1, time/1, current_time/1, format_time//2]).
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:- use_module(library(format)).
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:- use_module(library(iso_ext)).
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:- use_module(library(error)).
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:- use_module(library(dcgs)).
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:- use_module(library(lists)).
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:- use_module(library(charsio), [read_from_chars/2]).
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%% current_time(-T)
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%
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% Yields the current system time _T_ in an opaque form, called a
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% _time stamp_. Use `format_time//2` to describe strings that contain
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% attributes of the time stamp.
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current_time(T) :-
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'$current_time'(T0),
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read_from_chars(T0, T).
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%% format_time(FormatString, TimeStamp)//
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%
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% The nonterminal format_time//2 describes a list of characters that
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% are formatted according to a format string. Usage:
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%
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% ```
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% phrase(format_time(FormatString, TimeStamp), Cs)
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% ```
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%
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% TimeStamp represents a moment in time in an opaque form, as for
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% example obtained by `current_time/1`.
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%
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% FormatString is a list of characters that are interpreted literally,
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% except for the following specifiers (and possibly more in the future):
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%
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% | `%Y` | year of the time stamp. Example: 2020. |
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% | `%m` | month number (01-12), zero-padded to 2 digits |
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% | `%d` | day number (01-31), zero-padded to 2 digits |
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% | `%H` | hour number (00-24), zero-padded to 2 digits |
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% | `%M` | minute number (00-59), zero-padded to 2 digits |
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% | `%S` | second number (00-60), zero-padded to 2 digits |
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% | `%b` | abbreviated month name, always 3 letters |
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% | `%a` | abbreviated weekday name, always 3 letters |
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% | `%A` | full weekday name |
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% | `%j` | day of the year (001-366), zero-padded to 3 digits |
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% | `%%` | the literal `%` |
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%
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% Example:
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%
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% ```
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% ?- current_time(T), phrase(format_time("%d.%m.%Y (%H:%M:%S)", T), Cs).
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% T = [...], Cs = "11.06.2020 (00:24:32)".
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% ```
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format_time([], _) --> [].
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format_time(['%','%'|Fs], T) --> !, "%", format_time(Fs, T).
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format_time(['%',Spec|Fs], T) --> !,
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( { member(Spec=Value, T) } ->
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seq(Value)
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; { domain_error(time_specifier, Spec, format_time//2) }
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),
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format_time(Fs, T).
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format_time([F|Fs], T) --> [F], format_time(Fs, T).
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%% max_sleep_time(T)
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%
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% The maximum admissible time span for `sleep/1`.
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max_sleep_time(0xfffffffffffffbff).
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%% sleep(S)
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%
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% Sleeps for S seconds (a floating point number or integer).
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sleep(T) :-
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builtins:must_be_number(T, sleep),
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( T < 0 ->
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domain_error(not_less_than_zero, T, sleep/1)
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; max_sleep_time(N), T > N ->
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throw(error(representation_error(max_sleep_time), sleep/1))
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; '$sleep'(T)
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).
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% '$cpu_now' can be replaced by statistics/2 once that is implemented.
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:- meta_predicate time(0).
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:- dynamic(time_id/1).
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:- dynamic(time_state/2).
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time_next_id(N) :-
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( retract(time_id(N0)) ->
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N is N0 + 1
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; N = 0
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),
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asserta(time_id(N)).
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%% time(Goal)
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%
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% Reports the execution time of Goal.
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time(Goal) :-
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'$cpu_now'(T0),
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time_next_id(ID),
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setup_call_cleanup(asserta(time_state(ID, T0)),
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( call_cleanup(catch(Goal, E, (report_time(ID),throw(E))),
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Det = true),
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time_true(ID),
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( Det == true -> !
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; true
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)
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; report_time(ID),
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false
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),
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retract(time_state(ID, _))).
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time_true(ID) :-
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report_time(ID).
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time_true(ID) :-
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% on backtracking, update the stored CPU time for this ID
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retract(time_state(ID, _)),
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'$cpu_now'(T0),
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asserta(time_state(ID, T0)),
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false.
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report_time(ID) :-
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time_state(ID, T0),
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'$cpu_now'(T),
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Time is T - T0,
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( bb_get('$answer_count', 0) ->
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Pre = " ", Post = ""
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; Pre = "", Post = " "
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),
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format("~s% CPU time: ~3fs~n~s", [Pre,Time,Post]).
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/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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?- time((true;false)).
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%@ % CPU time: 0.006s
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%@ true
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%@ ; % CPU time: 0.001s
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%@ false.
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:- time(use_module(library(clpz))).
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%@ % CPU time: 3.711s
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%@ true.
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:- time(use_module(library(lists))).
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%@ % CPU time: 0.006s
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%@ true.
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?- time(member(X, "abc")).
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%@ % CPU time: 0.005s
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%@ X = a
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%@ ; % CPU time: 0.000s
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%@ X = b
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%@ ; % CPU time: 0.000s
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%@ X = c
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%@ ; % CPU time: 0.000s
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%@ false.
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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
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