aboutsummaryrefslogtreecommitdiffstats
path: root/lib/stdlib/test/calendar_SUITE.erl
diff options
context:
space:
mode:
authorStanislav Mayorov <[email protected]>2019-01-31 16:02:40 +0700
committerStanislav Mayorov <[email protected]>2019-01-31 16:16:39 +0700
commit27ccbe9779ddab2402a44d1a9639620ee704f634 (patch)
tree29e3a902956cb19d77e203403af34733404db3a9 /lib/stdlib/test/calendar_SUITE.erl
parent3825199794da28d79b21052a2e69e2335921d55e (diff)
downloadotp-27ccbe9779ddab2402a44d1a9639620ee704f634.tar.gz
otp-27ccbe9779ddab2402a44d1a9639620ee704f634.tar.bz2
otp-27ccbe9779ddab2402a44d1a9639620ee704f634.zip
Optimize calendar:gregorian_days_to_date/1
This patch improves the performance of calendar:gregorian_days_to_date/1 by changing the algorithm for finding the year to log-logarithmic. The old implementation has linear complexity, which makes function too slow for large values. For example: There is an API that allows you to create events for future dates. There are users of this API who, for some reasons, choose dates very far in the future. In such conditions, function works very slow. New implementation based on interpolation search, takes 1 or 2 iterations at most cases and free from such a flaw. A unit test was also developed to illustrate the speed of a function at large values.
Diffstat (limited to 'lib/stdlib/test/calendar_SUITE.erl')
-rw-r--r--lib/stdlib/test/calendar_SUITE.erl14
1 files changed, 13 insertions, 1 deletions
diff --git a/lib/stdlib/test/calendar_SUITE.erl b/lib/stdlib/test/calendar_SUITE.erl
index df62c0921d..c6d9dbca4a 100644
--- a/lib/stdlib/test/calendar_SUITE.erl
+++ b/lib/stdlib/test/calendar_SUITE.erl
@@ -24,6 +24,7 @@
-export([all/0, suite/0,groups/0,init_per_suite/1, end_per_suite/1,
init_per_group/2,end_per_group/2,
gregorian_days/1,
+ big_gregorian_days/1,
gregorian_seconds/1,
day_of_the_week/1,
day_of_the_week_calibrate/1,
@@ -36,13 +37,16 @@
-define(START_YEAR, 1947).
-define(END_YEAR, 2012).
+-define(BIG_START_YEAR, 20000000).
+-define(BIG_END_YEAR, 20000020).
+
suite() -> [{ct_hooks,[ts_install_cth]}].
all() ->
[gregorian_days, gregorian_seconds, day_of_the_week,
day_of_the_week_calibrate, leap_years,
last_day_of_the_month, local_time_to_universal_time_dst,
- iso_week_number, system_time, rfc3339].
+ iso_week_number, system_time, rfc3339, big_gregorian_days].
groups() ->
[].
@@ -67,6 +71,14 @@ gregorian_days(Config) when is_list(Config) ->
MaxDays = calendar:date_to_gregorian_days({?END_YEAR, 1, 1}),
check_gregorian_days(Days, MaxDays).
+%% Tests that date_to_gregorian_days and gregorian_days_to_date
+%% are each others inverses from ?BIG_START_YEAR-01-01 up to ?BIG_END_YEAR-01-01.
+%% At the same time valid_date is tested.
+big_gregorian_days(Config) when is_list(Config) ->
+ Days = calendar:date_to_gregorian_days({?BIG_START_YEAR, 1, 1}),
+ MaxDays = calendar:date_to_gregorian_days({?BIG_END_YEAR, 1, 1}),
+ check_gregorian_days(Days, MaxDays).
+
%% Tests that datetime_to_gregorian_seconds and
%% gregorian_seconds_to_date are each others inverses for a sampled
%% number of seconds from ?START_YEAR-01-01 up to ?END_YEAR-01-01: We check