5
votes
Accepted
Why computer didn't use cesium atom to define 1 second?
First of all, the reason personal computers dont't use atomic clocks based on caesium is price. One CSAC (chip scale atomic clock) costs 5000 USD nowadays. The added precision is not worth the price ...
- 1,589
5
votes
Accepted
What does it mean that HDLs "explicitly include the notion of time"?
Programming languages usually don't have a notion of time. They describe how things are sequenced, but usually they don't go further. When they do, that's relegated to the library part of the ...
- 3,024
5
votes
How to prove that a system is real-time?
It depends on your definition of "real-time system". A standard definition is: a system is real-time if it will respond within $T$ seconds, with probability at least $P$. Here you need to fill in ...
D.W.♦
- 154k
5
votes
Accepted
Priority inversion in Hoare and Mesa monitors
Unless you are careful priority inversion is possible in either Hoare type or Mesa type monitors. This is because monitors implement a form of mutual exclusion (only one process can be "in" the ...
- 17.6k
4
votes
What guarantees do "soft" real-time operating systems actually provide
To define "soft real-time," it is easiest to compare it with "hard real-time."
Speaking casually, most people implicitly have an informal mental model that considers information or an event as being "...
4
votes
Accepted
If current time in milliseconds is considered good enough random seed for a pseudorandom number generator, why not just use that time directly?
The key property that we want from (non-cryptographic) pseudorandom numbers is that they "look" independent. In particular, say you have some algorithm that requires a PRNG to perform well and you ...
- 241
3
votes
If current time in milliseconds is considered good enough random seed for a pseudorandom number generator, why not just use that time directly?
It's not random. It increases by 1 every milliseconds. In computer terms, it stays unchanged for a loooooong time (millions of clock cycles).
But current system time in milliseconds is most ...
- 27.8k
3
votes
Accepted
How to prove that a system is real-time?
You need to provide a more precise description of your system and real-time
requirements.
If you are interested in only the timeliness and timeliness predictability of
the response to the first event,...
3
votes
What is 'real time' in a Computer Vision context?
In computer science, a real-time computing (RTC) system is one that guarantees a response before a previously set deadline.
For a stream of images, that implies that a real-time system is one that ...
- 886
3
votes
What is 'real time' in a Computer Vision context?
There is no one answer to this question. "Real time" can mean very different things, depending on what kind of sensor or sensors you are using, and what you are trying to do. By the way, editing and ...
- 568
2
votes
Accepted
Are there any efficient algorithems to find packets similarities in a list?
There are many possible approaches for measuring document similarity:
edit distance
shingling
Jaccard similarity
TF-IDF and cosine similarity
https://stackoverflow.com/q/101569/781723
https://...
D.W.♦
- 154k
2
votes
What does it mean that HDLs "explicitly include the notion of time"?
Imperative languages only implicitly have a notion of time. Primarily, demarcated by mutation of state, i.e. there's a before some variable was mutated and an after some variable was mutated. ...
2
votes
Accepted
timed automata - advance only in certain states
So, after looking deeper into the subject I found the solution. Posting in case somebody else needs an answer and is unfamiliar with the subject.
What I was looking for is called a Stopwatch ...
- 151
2
votes
Accepted
UTC Time Offset
The timestamp you are seeing is the time in the given timezone using the given offset from UTC. The specific format of the timestamp you are looking at is an RFC2822 formatted timestamp which means ...
- 156
2
votes
Which overhead is smaller - function call or passing variables between processes?
callback-based approach requires you to call a callback function every time you receive a new data packet; this is not a good approach for high-load and high-throughput network servers
Who claims ...
- 746
1
vote
Missing 770201 seconds in Y2K2038
I think you have an error in your math. 19 January 2038 at 03:14:07 UTC is $t_1 = 2147483647$ seconds after the epoch. 13 December 1901 at 20:45:52 is $t_2 = 2147483648$ seconds before the epoch.
...
- 27.4k
1
vote
preprocessing or real time for magnification of portions of video
Not knowing your specific usage, I'd use Isadora or TouchDesign for these kind of task. They can help you manipulate realtime feeds based on the events
- 11
1
vote
Real-time systems and real-time operating systems
A system is several things working together. A real time system might include computer hardware and software. Depending on where you draw the line it might include sensors and actuators reaching into ...
- 416
1
vote
Determine deadline for periodic task that enter ready queue in RTOS
You can't generate a deadline from nothing. That doesn't make sense.
Some tasks must be completed by a certain time, or they are useless. Only the programmer who writes the task knows whether this ...
D.W.♦
- 154k
1
vote
Wrapping the complexities of alternative algorithms: What is the proper "term" for it?
Hybrid algorithms.
In sorting algorithms it's rather common, Start with quicksort and if the size of the array is small enough switch to insertion sort (much faster for small $n$). Additionally when ...
- 4,276
1
vote
Rate Monotonic maximum execution time
First of all, this problem is (weakly) NP-hard, see this paper by Ekberg and Yi, because it generalizes the problem of deciding which task sets are schedulable by Rate Monotonic.
However, assuming ...
- 3,252
1
vote
What does it mean that HDLs "explicitly include the notion of time"?
HDL's incorporate a notion of time in the following sense: they may allow you to talk about the current value of the circuit's state (e.g., registers) and the next value of its state. So, you might ...
D.W.♦
- 154k
1
vote
Real time application with DFA or NFA application
A real time application is one in which some computation needs to be done very fast, always. For example, controlling an airplane, decoding an MPEG, and Skype are real time applications. Web browsing ...
- 274k
1
vote
Real time application with DFA or NFA application
DFA/NFA in a real time application ? consider designing a parser for user inputs where each input is a word w="http://some-address.com?key[1]=value1&key[2]=value2..."
consider having each key[i] ...
- 62
Only top scored, non community-wiki answers of a minimum length are eligible