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Questions tagged [threads]

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Can many threads run in a parallel in many-to-one model?

The book I am reading suggests that in a many-to-one multi-threading model, the threads are unable to run in parallel in a multi-core system. I am thinking this is not the case because if we have many-...
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1answer
39 views

Does this lock have a name (related to reader-writer lock)

The object can be locked two different ways, where if the lock is entered the same way a second time, the lock is recursive, but if it's entered the other way, it blocks. Like a reader-writer lock, ...
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28 views

What does it mean by “consistent view of memory” in lock-free dequeue implementation?

I am currently reading this paper by Chales-Lev. This paper explain an implementation of work-stealing dequeue. The part where I don't understand is in the implementation of steal operation. ...
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21 views

Parallel Thread Processing Variable Question

if there is a better stack exchange suited for this question please inform me. say you have a thread that is constantly checking the state of a variable in 2 ms intervals ...
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51 views

Parallel algorithms with desired sequential workload

Could you share any known algorithm which leans on following patterns? These patterns have both multithreaded and sequential workload. Those algorithms need to be joined to complete some sequential ...
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1answer
15 views

multithreading - duration of jobs

" How long will it take for 2 jobs to complete if they're running in parallel, knowing that both have a total of 20 minutes of CPU usage time and 50% IO" I calculated the CPU usage: ...
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1answer
32 views

Threads and Operating System

In a computer, the processor executes different threads and changes between them, the operating system is a program at the end that it´s being executed by the processor, there exists the posibility ...
3
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1answer
73 views

What should be the minimum value when the two threads are executed concurrently

int count=0; void *thfunc() { int ctr=0; for(ctr=0;ctr<100;ctr++) count++; } If *thfunc() is executed by two threads concurrently in a uniprocessor ...
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2answers
83 views

Why are threads called the unit of dispatch?

Threads called the "unit of dispatch" but what does that mean? I was looking over the web and two operating systems books but I can't find the answer. It seems that processes are defined by two ...
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1answer
600 views

About hardware multithreading

I'm reading Multithreading (computer architecture) - Wiki, aka hardware threading, and I'm trying to understand the second paragraph: (p2): Where multiprocessing systems include multiple complete ...
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47 views

How is switching among user-level threads realised in the user space?

This is with respect to user-level threads where the kernel only knows about the process as a whole, and threads are created and maintained in the user space. Each thread has its PC, registers, stack ...
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1answer
46 views

Reason for thread pooling

Can someone explain what is the reason for thread-pooling in Linux, even if the threads are light to create and destroy??
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0answers
30 views

Definition of PrefixSum function

I came across this paper and attempting to go through the implementation of randomized selection algorithm on page 8. Step 1 of the algorithm suggest to compute $s = PrefixSum(n_i, p)$. Where $p$ is ...
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22 views

User-level threads and information available to the kernel

User-level threads are transparent to the kernel. How is htop able to show user-level threads running on my system? I know that those threads are user-level threads ...
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1answer
25 views

Can Multiprocessor Systems Implement Both Temporal Multithreading and Simultaneous Multithreading?

I am aware that multiprocessor systems often implement simultaneous multithreading in order to allow multiple threads to run on different CPUs. I am also aware that uni-core systems often implement ...
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1answer
59 views

What is the Difference Between Many-to-Many (M:M) Threading and Hybrid (M:N) Threading?

I have been researching threading and come across several websites which all say contradicting statements about which and how many thread models exist. Some websites say there are only three: 1:1, M:1 ...
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31 views

semaphore for two groups of processes

Can someone help me giving a pseudo code to this problem : There are two groups of processes , A and B. Maximum 3 Processes from group A or group B(only from one group) can use the given resource . ...
3
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1answer
94 views

What is the benefit of using one to one thread mapping model instead of Many to Many or two level?

So in the silberschatz O.S book it says Windows uses one to one model (mapping user level threads to kernel level threads) but why? i thought many to many and two level models are much better, ...
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1answer
33 views

Why is there no one to many Multithreading Model?

I am studying various multi-threading models. Here the user threads are mapped to Kernel Threads. They are - ...
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2answers
53 views

What is the difference between a page and thread?

"Each process that is executed is divided into blocks of same size, called pages." "Thread is a part of process being executed." Are pages and threads both part(s) of process? Whats the difference ...
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1answer
115 views

Work-stealing: where and how many to steal

If one ignores the conflicts when accessing the dequeue in Work-Stealing algorithms, does it matter (and in what ways) if one steals from the top or bottom (or anywhere randomly) of the dequeue? Does ...
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1answer
22 views

Need to understand signals received vs sent

What is meant by in the following statement (from the paper titled "Implementing Lightweight Threads"): As in singlethreaded processes, the number of signals received by the process is less than ...
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1answer
132 views

Hardware thread context and register renaming

I'm having some issues understanding what happens on a context switch with the physical register file in an out-of-order CPU that implements context switching. Suppose that a CPU consists of 4 ...
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1answer
2k views

What is “time-slice multi-threading”?

My goal is to understand the exact differences between SoEMT, SMT and "time-slice multi threading". Thus far I already found information on SoEMT and SMT and it does not seem to hard to find more on ...
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1answer
130 views

Multi-threading : N cores = N times one core?

This question is about modern CPU architectures and multi-threading. I'm mainly interested in personal computers or servers having 2, 4, 8, 16... cores like for example an Intel core i7. I mean not a ...
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0answers
47 views

Is a single starved process considered deadlocked?

In regard to the critical section problem, an algorithm that switches between allowing one of two processes, P1 or P2, to complete their critical section would cause starvation for P1 if P2 stayed in ...
2
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1answer
275 views

Understanding google's user level threads in kernel threads

I came across Paul Turner work on increasing efficiency of M:N threading model. I am not able to grasp the concept at slide 18 of LPC-User-Threading It says : for two threads ...
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0answers
133 views

Algorithm to construct timeline graph with arrival and departure times

So I am trying to construct a timeline graph for threads interacting with synchronization functions e.g. pthread_mutex_lock. I have the following information: 1- ...
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1answer
63 views

What do `i` and `Number` represent in the Bakery Algorithm?

I am studying the bakery algorithm, and I am unsure of what the variable i represents in it. I understand that Entering ...
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1answer
458 views

How can context switch affect the modification of a variable?

float myTotalAmount=0; void update(float amt){ myTotalAmount+= amt; } Task A called update(10); Calculated ...
4
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1answer
104 views

Is there a generic word for “thread or process”?

I'm writing about a problem that could be caused by race conditions between multiple threads, or OS-level processes on the same machine or different machines, or VM-level processes like the Erlang VM ...
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3answers
1k views

Why are most mutex implementations unfair?

My understanding is that most popular implementations of a mutex (e.g. std::mutex in C++) do not guarantee fairness -- that is, they do not guarantee that in instances of contention, the lock will be ...
3
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1answer
50 views

One rational interval function and one irrational, will they ever collide?

This question may be a little mathy or hardware-y, so I may have to ask elsewhere. I've recently learned that if a is a positive rational number and b is a positive irrational number, there exists no ...
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0answers
336 views

Do user level threads take advantage of multi processing?

I asked this question here on stackoverflow, but maybe because of off-topic over there, it didn't received proper response. Does user level threads take advantage of multiprocessing ? I read one such ...
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1answer
1k views

thread scheduling in multi core architecture

In multi core architecture, let us say we have M cores and N threads (N > M) and a process once assigned to a core can't migrate to another core's ready queue. We have to design scheduling policy to ...
2
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0answers
173 views

many to many multithreading

In many to many multithreading model the processor threads are multiplexed to a lesser or equal number of kernel threads. What exactly does it mean?? Does it mean that if a kernel is executing a ...
1
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2answers
5k views

How does RAM is shared in multi core environment?

I learnt that multi core processors have more than one processing units( i.e. the main executing units ALU etc.) and they are better at performance. I want to know how they share Physical memory. I'll ...
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1answer
146 views

Can threads use resources from other processes?

This is how I see threads. Please do correct me if I'm wrong: A thread is a part of a process that runs a sequence of program code. There can be many threads within a process that run different ...
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2answers
102 views

What does it mean that a core supports 2 threads?

I understand that a process may have multiple threads, and that a processor may have multiple cores to run processes in parallel. But I can't understand how a core may allow multiple threads, what ...
4
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1answer
135 views

What techniques could be used to support thread-local contexts and resources in a language?

I am interested in the subject of thread-local contexts, which is a feature that I use quite often in solutions, but seems to lack first-class support in any languages I have used. Quite often in ...
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1answer
1k views

Why is quiescent consistency compositional, but sequential consistency is not

I'm having trouble in comparing these two memory consistency models. Essentially for sequential consistency I think of real code like this: ...
4
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1answer
2k views

Difference between IO threads and worker threads

I have read that NodeJs is able to support hundreds and thousand of concurrent calls because the worker threads do not wait on the IO calls to complete. They use event driven IO. Similarly in .NET we ...
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1answer
75 views

What is extra thread for idle time

Here http://tomstechnicalblog.blogspot.com/2016/02/rxjava-understanding-observeon-and.html I've found a sentence which I do not understand: If you have a quad-core, you can optimally support 5 ...
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1answer
93 views

Is it correct to say that CPU's only compute threads?

New to the world of parallel computation. Would it be correct to say that CPU's are actually thread calculators? My understanding currently: a ...
2
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1answer
2k views

User level threads are transparent to the kernel?

Find whether given statement True or False? Explain. User level threads are transparent to the kernel? My attempt : False. Since, user level threads are managed by a user level library however, ...
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2answers
820 views

Why are multi-threading programs more prone to errors?

Why are multi-threading programs more prone to errors than single threaded programs ? or why is multi-threading programming one of the areas where developers are (more) prone to errors? Is this in ...
2
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2answers
2k views

Why there must be a relationship between user threads and kernel threads?

The following is an excerpt from OS concepts by galvin.Here is the book. Multithreading Models Our discussion so far has treated threads in a generic sense. However, support for threads may ...
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1answer
48 views

How do threads decide when to 'go'? [closed]

I have written some code that animates two boxes using HTML5 and JavaScript threads. I set them up to move at a fixed rate, which is the same: ...
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4answers
39k views

What threads share in general?

Well this is general question. And if anyone want to make it implementation specific then I will prefer Unix related stuff. But first need to know following problems in generality: I read single ...
4
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1answer
126 views

Does a reentrant list for signal queue in a single-thread environment exist?

I need to handle Unix signals in a single-threaded application with the following goals: Signals doesn't mask on receive (thus, the signal handler must be reentrant). I am not allowed to lose signal ...