Questions tagged [real-time]

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Deadline Monotonic formula with same priority

I have a question related with the response time of Deadline Monotonic scheduling...let's assume that there are 4 tasks, and the processor only allows to have 3 task priorities, thus there will be 2 ...
DeadlyKitten999's user avatar
1 vote
1 answer
49 views

Missing 770201 seconds in Y2K2038

From what I understand about the Y2K38 problem, unpatched 32 bit systems with signed UTC times will jump back from 19 January 2038 at 03:14:07 UTC to 13 December 1901, at 20:45:52. Calculating the ...
Daniël van den Berg's user avatar
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Worst Case Response Time (WCRT) analysis the only necessary test for real time tasks?

Recently, I have taken a Computer Science exam for the course Operating Systems. One question was as follows: Which statements about real-time operating systems are true? I selected two options, but ...
Daniel's user avatar
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1 vote
1 answer
112 views

How to simulate a Discrete Event Simulation model with a real-time server?

My Problem is having to work with real-time server in a DES model. I have the following situation: I want to build a discrete event simulation model (Using event scheduling world view). However, this ...
M. Pour's user avatar
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1 answer
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Why computer didn't use cesium atom to define 1 second?

As far I know computer using crystal oscilator to define 1 second and it's not real 1 second, i mean it's not stable. While real clock using cesium and we know cesium is stable, why doesn't computer ...
Muhammad Ikhwan Perwira's user avatar
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1 answer
14 views

preprocessing or real time for magnification of portions of video

Im new at CS and would like to gather preliminary information to approach an interactive art project. I want to construct a grid of videos - think about a matrix M = m x n where Mi,j is a video that ...
user305883's user avatar
1 vote
2 answers
115 views

UTC Time Offset

Really confused about the meaning of offset in email headers. Header date reads as: Sat, 8 Jun 2019 11:45:15 −0500 Does the time shown 11:45:15 is the actual time ...
Raptor's user avatar
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1 answer
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Which overhead is smaller - function call or passing variables between processes?

the question is related to networking frameworks; 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 ...
ivan866's user avatar
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What algorithm to use for substractive machining RT simulation?

For a CAM (Computer Aided Manufacturing) software, and more specifically, for the simulation of the subtractive manufacturing, I would like to understand how to design the representation. In ...
Adrian Maire's user avatar
2 votes
1 answer
323 views

Early Deadline First (EDF) scheduling in real-time systems feasibility test proof

I am trying to prove Theorem 6.2 on page 127 of the book Real-Time Systems by Jane W. S. Liu: http://www.cse.hcmut.edu.vn/~thai/books/2000%20_%20Liu-%20Real%20Time%20Systems.pdf It is based on Early ...
Matt's user avatar
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Real-time systems and real-time operating systems

Just to understand the topic a little bit better, I would like to know if there is a difference between real-time systems and real-time operating systems. I know that a real-time system is a system ...
Guest's user avatar
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What is the best algorithm for detecting the texture of a person's clothes in real-time for a mobile robot?

I am working on the human following robot. the robot extracts a feature of clothes's texture and distinguishes between the people that they stand up in front of the robot. So, the robot needs that it ...
Redhwan's user avatar
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2 votes
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40 views

Why can't OS's keep audio and video recording in sync?

It seems every program that purports to record webcams fails to keep audio and video in sync. Moreover, there are probably man millenia being spent by people trying to correct for this during editing....
James Bowery's user avatar
3 votes
2 answers
1k views

If current time in milliseconds is considered good enough random seed for a pseudorandom number generator, why not just use that time directly?

I was reading about pseudorandom number generators and how they need a seed and how that seed is usually current system time in milliseconds. One of the most common algorithms is the linear ...
stackzebra's user avatar
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1 answer
28 views

Wrapping the complexities of alternative algorithms: What is the proper "term" for it?

Suppose that we have two algorithms for the same task (e.g. search): AlgC: has bounded worst-case complexity, e.g. O(n.logn) AlgH: is a heuristic algorithm that is experimentally faster than AlgC, ...
Ali's user avatar
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1 vote
1 answer
274 views

Rate Monotonic maximum execution time

There are several periodic tasks (Period, Execution time), e.g.: A = (20, 9) B = (12, 4) C = (4, X) What methods/tests can be used for finding the maximum execution time X for which the task ...
Václav Struhár's user avatar
2 votes
0 answers
53 views

Agreeing on a Time in a Trustless Network

Imagine a chord-like network $N$. each machine $m \in N$ is directly connected to $N_m \subset N$. Without relying on official timeservers, I want all machines to synchronize to some time with ...
option 12's user avatar
2 votes
0 answers
41 views

Avoiding collisions in space and time

Say I have an image, represented as a 2D array of pixel values. Also, say I have a set of points on that image where each has a current (x, y) position and a Destination (x, y) associated with it. I ...
Michael O'Brien's user avatar
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0 answers
316 views

Utilization Factor, periodic tasks and schedulability

We have 2 periodic tasks that start at the same moment in a monocore processor. Why can happen that, even if the utilization factor is <= 1, the 2 periodic tasks are not schedulable ? For example, ...
Qwerto's user avatar
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3 votes
1 answer
66 views

timed automata - advance only in certain states

I am currently looking into timed automata for a project. I am thinking about a timed automaton where a clock only advances when the automaton is in a certain state. However, my little knowledge in ...
stklik's user avatar
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1 answer
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Determine deadline for periodic task that enter ready queue in RTOS

I am currently trying to optimise the scheduler of FreeRTOS and in general Real-Time Operating Systems as a Project. In FreeRTOS, and I suspect other RTOS as well, we don't specify the deadline for ...
Sidhin S Thomas's user avatar
4 votes
3 answers
349 views

What does it mean that HDLs "explicitly include the notion of time"?

I got onto the topic of HDLs (Hardware Description Languages) from a comment elsewhere on this site. The Wikipedia article states, rather tantalizingly: One important difference between most ...
Wildcard's user avatar
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1 vote
2 answers
327 views

How to prove that a system is real-time?

I'm writing a paper on the system I designed which upon receiving an event, performs a number of calculations and publishes the result to several subscribers. I can calculate the amount of time it ...
ePezhman's user avatar
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Neural networks fed with training data on demand?

What I want to achieve is to build a neural network with Keras which will have to stabilize a quadcopter I've built. The network would have three inputs: pitch, roll, yaw, acceleration x, accel y and ...
artus9033's user avatar
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why p1 misses it first deadline? Rate monotonic scheduling

I understand that rate monotonic scheduling assigns a priority to a process based on the periodicity of the tasks it generates and the process with the shortest inter-task period has the highest ...
Ankit Rageme's user avatar
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1 answer
61 views

Are there any efficient algorithems to find packets similarities in a list?

I would like to make a program which finds similar packets (there might be more then one class of similarity) in packet list (which is updated all the time). Are there any efficient algorithems to ...
Adi Ml's user avatar
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1 vote
2 answers
1k views

Real time application with DFA or NFA application

Can anyone here give an example of DFA or NFA real time application? And, can I know what are complexity and decidability problems in real time application? Does every real time application have ...
brendan's user avatar
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1 vote
3 answers
4k views

What is 'real time' in a Computer Vision context?

Suppose you have a program which works on a stream of images. It gets an image, makes edits and stores the image. What is the maximum latency with which one can still speak of a "real time application"...
Martin Thoma's user avatar
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1 answer
449 views

Rate Monotonic First Fit vs. Rate Monotonic Next Fit vs. Proportionate Fair

What would an example of a set of tasks be, where RMFF, RMNF and P-Fair all result in a different number of processors required?
JollyGr33nGiant's user avatar
5 votes
1 answer
512 views

Priority inversion in Hoare and Mesa monitors

I understand the difference between Hoare and Mesa monitors. However I don't understand why priority inversion (when a lower priority process gets done before a higher priority process) is possible in ...
FutureTrillionaire's user avatar
1 vote
0 answers
311 views

Optimality of EDF

For Earliest Deadline First, I have read that if utilization is less or equal to 1, the task set is schedulable under EDF. But does this criteria expresses the optimality for EDF? If not, how can we ...
Dumbo's user avatar
  • 111
-1 votes
1 answer
91 views

Probabilistic Analysis in real time network : Error in data and feedback channel. Two users communication

I'm studying probabilistic analysis in real time network. We have learned how many attempts in average are required to transmit a packet when there is no error on the feedback channel. With no error ...
Jérôme Detournay's user avatar
2 votes
1 answer
2k views

A real-world example for a kind of real-time applications

I submitted a paper regarding hard real-time systems to an engineering journal. But the referees generally agreed my task model is too limited. My task model is a frame-based real-time application ...
Code's user avatar
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5 votes
1 answer
1k views

Can multiple tasks in an RTOS share one stack to save memory?

Many small embedded systems have a limited amount of RAM, 10k or less. I know you can run an RTOS on such systems, however, a realistic number of tasks in such a system is very low, mainly because ...
Johan Bezem's user avatar
18 votes
3 answers
3k views

What guarantees do "soft" real-time operating systems actually provide

I think I know what a "hard" real-time operating system is. It is an operating system with a scheduler that provides a contract with the application programmer. An application provides a deadline ...
Wandering Logic's user avatar
6 votes
1 answer
348 views

Realtime hardware/software versus PC software/hardware, how are these distinct and alike?

This question stems from a few answers and comments on a question I posted in signal processing found here. I guess I am a little confused. Are there any concrete differences between realtime ...
KDecker's user avatar
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