Mixing
Number of occurrences of a generic recurring event between two dates
$begingroup$
Intro
Cron is a very common tool in computer science, which allows to schedule an event given a generic pattern written in a file called crontab. I'm researching on an algorithm to calculate the number of times a given generic recurring event is going to happen between two given dates (timestamps)
Problem
- Given a generic starting date
- Unix Timestamp 636015272
- Date: Tue, 26-02-1990 GMT 6:54:32 am)
- Given a generic end date
- Unix Timestamp 1542749251:
- Date: Tue 20-11-2018 GMT 9:27:31 pm)
- Given a generic recurring event expression(Crontab)
How many times the recurring event has been triggered between both dates?
Extra comments
The solution must be O(1), by just using calculations between the two given timestamps. This means: it is not valid to recursively increase or decrease a time interval interval to check if the solution is on bounds
Crontab expressions are expressed in UTC, cosiderations such as daylight saving can be ignored
Extra simplifications, such as removing day of the week can also be considered
So far, the problem seems duable by using modular arithmetics and handling many different inputs using particular logic for each case. However, the complexity of handling particularly cases gets really high. It would be nice having some models, or general algebraic functions to make the calculation.
computer-science calendar-computations
asked Jan 26 at 18:35
BuendiadasBuendiadas
114
$endgroup$
add a comment |
$begingroup$
Intro
Cron is a very common tool in computer science, which allows to schedule an event given a generic pattern written in a file called crontab. I'm researching on an algorithm to calculate the number of times a given generic recurring event is going to happen between two given dates (timestamps)
Problem
- Given a generic starting date
- Unix Timestamp 636015272
- Date: Tue, 26-02-1990 GMT 6:54:32 am)
- Given a generic end date
- Unix Timestamp 1542749251:
- Date: Tue 20-11-2018 GMT 9:27:31 pm)
- Given a generic recurring event expression(Crontab)
How many times the recurring event has been triggered between both dates?
Extra comments
The solution must be O(1), by just using calculations between the two given timestamps. This means: it is not valid to recursively increase or decrease a time interval interval to check if the solution is on bounds
Crontab expressions are expressed in UTC, cosiderations such as daylight saving can be ignored
Extra simplifications, such as removing day of the week can also be considered
So far, the problem seems duable by using modular arithmetics and handling many different inputs using particular logic for each case. However, the complexity of handling particularly cases gets really high. It would be nice having some models, or general algebraic functions to make the calculation.
computer-science calendar-computations
asked Jan 26 at 18:35
BuendiadasBuendiadas
114
$endgroup$
$begingroup$
is the implementation of crond such that we can ignore daylight saving if we consider the unix timestamp?
$endgroup$
– LinAlg
Jan 28 at 20:49
$begingroup$
Good question, we can ignore daylight saving, and consider always UTC, I will add it into the descriptioon
$endgroup$
– Buendiadas
Jan 28 at 22:44
$begingroup$
@LinAlg So far in my calculations, Day of Week also increased the complexity considerably. In order to simplify and get somewhere, this is something I'm also considering initially to ignore.
$endgroup$
– Buendiadas
Jan 28 at 22:58
$begingroup$
What happened to the bounty?
$endgroup$
– LinAlg
Feb 5 at 21:42
add a comment |
$begingroup$
Intro
Cron is a very common tool in computer science, which allows to schedule an event given a generic pattern written in a file called crontab. I'm researching on an algorithm to calculate the number of times a given generic recurring event is going to happen between two given dates (timestamps)
Problem
- Given a generic starting date
- Unix Timestamp 636015272
- Date: Tue, 26-02-1990 GMT 6:54:32 am)
- Given a generic end date
- Unix Timestamp 1542749251:
- Date: Tue 20-11-2018 GMT 9:27:31 pm)
- Given a generic recurring event expression(Crontab)
How many times the recurring event has been triggered between both dates?
Extra comments
The solution must be O(1), by just using calculations between the two given timestamps. This means: it is not valid to recursively increase or decrease a time interval interval to check if the solution is on bounds
Crontab expressions are expressed in UTC, cosiderations such as daylight saving can be ignored
Extra simplifications, such as removing day of the week can also be considered
So far, the problem seems duable by using modular arithmetics and handling many different inputs using particular logic for each case. However, the complexity of handling particularly cases gets really high. It would be nice having some models, or general algebraic functions to make the calculation.
computer-science calendar-computations
asked Jan 26 at 18:35
BuendiadasBuendiadas
114
$endgroup$
Intro
Cron is a very common tool in computer science, which allows to schedule an event given a generic pattern written in a file called crontab. I'm researching on an algorithm to calculate the number of times a given generic recurring event is going to happen between two given dates (timestamps)
Problem
- Given a generic starting date
- Unix Timestamp 636015272
- Date: Tue, 26-02-1990 GMT 6:54:32 am)
- Given a generic end date
- Unix Timestamp 1542749251:
- Date: Tue 20-11-2018 GMT 9:27:31 pm)
- Given a generic recurring event expression(Crontab)
How many times the recurring event has been triggered between both dates?
Extra comments
The solution must be O(1), by just using calculations between the two given timestamps. This means: it is not valid to recursively increase or decrease a time interval interval to check if the solution is on bounds
Crontab expressions are expressed in UTC, cosiderations such as daylight saving can be ignored
Extra simplifications, such as removing day of the week can also be considered
So far, the problem seems duable by using modular arithmetics and handling many different inputs using particular logic for each case. However, the complexity of handling particularly cases gets really high. It would be nice having some models, or general algebraic functions to make the calculation.
computer-science calendar-computations
computer-science calendar-computations
asked Jan 26 at 18:35
BuendiadasBuendiadas
114
asked Jan 26 at 18:35
BuendiadasBuendiadas
114
edited Jan 28 at 23:03
Buendiadas
asked Jan 26 at 18:35
BuendiadasBuendiadas
114
asked Jan 26 at 18:35
BuendiadasBuendiadas
114
asked Jan 26 at 18:35
BuendiadasBuendiadas
114
114
$begingroup$
is the implementation of crond such that we can ignore daylight saving if we consider the unix timestamp?
$endgroup$
– LinAlg
Jan 28 at 20:49
$begingroup$
Good question, we can ignore daylight saving, and consider always UTC, I will add it into the descriptioon
$endgroup$
– Buendiadas
Jan 28 at 22:44
$begingroup$
@LinAlg So far in my calculations, Day of Week also increased the complexity considerably. In order to simplify and get somewhere, this is something I'm also considering initially to ignore.
$endgroup$
– Buendiadas
Jan 28 at 22:58
$begingroup$
What happened to the bounty?
$endgroup$
– LinAlg
Feb 5 at 21:42
add a comment |
$begingroup$
is the implementation of crond such that we can ignore daylight saving if we consider the unix timestamp?
$endgroup$
– LinAlg
Jan 28 at 20:49
$begingroup$
Good question, we can ignore daylight saving, and consider always UTC, I will add it into the descriptioon
$endgroup$
– Buendiadas
Jan 28 at 22:44
$begingroup$
@LinAlg So far in my calculations, Day of Week also increased the complexity considerably. In order to simplify and get somewhere, this is something I'm also considering initially to ignore.
$endgroup$
– Buendiadas
Jan 28 at 22:58
$begingroup$
What happened to the bounty?
$endgroup$
– LinAlg
Feb 5 at 21:42
$begingroup$
is the implementation of crond such that we can ignore daylight saving if we consider the unix timestamp?
$endgroup$
– LinAlg
Jan 28 at 20:49
$begingroup$
is the implementation of crond such that we can ignore daylight saving if we consider the unix timestamp?
$endgroup$
– LinAlg
Jan 28 at 20:49
$begingroup$
Good question, we can ignore daylight saving, and consider always UTC, I will add it into the descriptioon
$endgroup$
– Buendiadas
Jan 28 at 22:44
$begingroup$
Good question, we can ignore daylight saving, and consider always UTC, I will add it into the descriptioon
$endgroup$
– Buendiadas
Jan 28 at 22:44
$begingroup$
@LinAlg So far in my calculations, Day of Week also increased the complexity considerably. In order to simplify and get somewhere, this is something I'm also considering initially to ignore.
$endgroup$
– Buendiadas
Jan 28 at 22:58
$begingroup$
@LinAlg So far in my calculations, Day of Week also increased the complexity considerably. In order to simplify and get somewhere, this is something I'm also considering initially to ignore.
$endgroup$
– Buendiadas
Jan 28 at 22:58
$begingroup$
What happened to the bounty?
$endgroup$
– LinAlg
Feb 5 at 21:42
$begingroup$
What happened to the bounty?
$endgroup$
– LinAlg
Feb 5 at 21:42
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
Let us omit the 'day of week' field for now, and only focus on year, month, dayofmonth, hours, and minutes.
You can decompose the number of cron runs in three different time intervals: the first day, the last day, and the in-between days. The first and the last day are independent on the interval, so any method gives you the $mathcal{O}(1)$ ressult.
Let us therefore focus on the number of in-between days. To count those, you first count the number of Januarys, Februarys in non-leap years, Februarys in leap years, Marches, etc. Converting those month counts to days is trivial, and you multiplying that with the number of hours at which it runs and the number of minutes at which it runs to get the total number of runs on in-between days.
answered Jan 31 at 18:01
LinAlgLinAlg
10.1k1521
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add a comment |
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1 Answer
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$begingroup$
Let us omit the 'day of week' field for now, and only focus on year, month, dayofmonth, hours, and minutes.
You can decompose the number of cron runs in three different time intervals: the first day, the last day, and the in-between days. The first and the last day are independent on the interval, so any method gives you the $mathcal{O}(1)$ ressult.
Let us therefore focus on the number of in-between days. To count those, you first count the number of Januarys, Februarys in non-leap years, Februarys in leap years, Marches, etc. Converting those month counts to days is trivial, and you multiplying that with the number of hours at which it runs and the number of minutes at which it runs to get the total number of runs on in-between days.
answered Jan 31 at 18:01
LinAlgLinAlg
10.1k1521
$endgroup$
add a comment |
$begingroup$
Let us omit the 'day of week' field for now, and only focus on year, month, dayofmonth, hours, and minutes.
You can decompose the number of cron runs in three different time intervals: the first day, the last day, and the in-between days. The first and the last day are independent on the interval, so any method gives you the $mathcal{O}(1)$ ressult.
Let us therefore focus on the number of in-between days. To count those, you first count the number of Januarys, Februarys in non-leap years, Februarys in leap years, Marches, etc. Converting those month counts to days is trivial, and you multiplying that with the number of hours at which it runs and the number of minutes at which it runs to get the total number of runs on in-between days.
answered Jan 31 at 18:01
LinAlgLinAlg
10.1k1521
$endgroup$
add a comment |
$begingroup$
Let us omit the 'day of week' field for now, and only focus on year, month, dayofmonth, hours, and minutes.
You can decompose the number of cron runs in three different time intervals: the first day, the last day, and the in-between days. The first and the last day are independent on the interval, so any method gives you the $mathcal{O}(1)$ ressult.
Let us therefore focus on the number of in-between days. To count those, you first count the number of Januarys, Februarys in non-leap years, Februarys in leap years, Marches, etc. Converting those month counts to days is trivial, and you multiplying that with the number of hours at which it runs and the number of minutes at which it runs to get the total number of runs on in-between days.
answered Jan 31 at 18:01
LinAlgLinAlg
10.1k1521
$endgroup$
Let us omit the 'day of week' field for now, and only focus on year, month, dayofmonth, hours, and minutes.
You can decompose the number of cron runs in three different time intervals: the first day, the last day, and the in-between days. The first and the last day are independent on the interval, so any method gives you the $mathcal{O}(1)$ ressult.
Let us therefore focus on the number of in-between days. To count those, you first count the number of Januarys, Februarys in non-leap years, Februarys in leap years, Marches, etc. Converting those month counts to days is trivial, and you multiplying that with the number of hours at which it runs and the number of minutes at which it runs to get the total number of runs on in-between days.
answered Jan 31 at 18:01
LinAlgLinAlg
10.1k1521
answered Jan 31 at 18:01
LinAlgLinAlg
10.1k1521
answered Jan 31 at 18:01
LinAlgLinAlg
10.1k1521
answered Jan 31 at 18:01
LinAlgLinAlg
10.1k1521
10.1k1521
add a comment |
add a comment |
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$begingroup$
is the implementation of crond such that we can ignore daylight saving if we consider the unix timestamp?
$endgroup$
– LinAlg
Jan 28 at 20:49
$begingroup$
Good question, we can ignore daylight saving, and consider always UTC, I will add it into the descriptioon
$endgroup$
– Buendiadas
Jan 28 at 22:44
$begingroup$
@LinAlg So far in my calculations, Day of Week also increased the complexity considerably. In order to simplify and get somewhere, this is something I'm also considering initially to ignore.
$endgroup$
– Buendiadas
Jan 28 at 22:58
$begingroup$
What happened to the bounty?
$endgroup$
– LinAlg
Feb 5 at 21:42