Questions tagged [threads]

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How do I call it when on Multi-threading I have a depency on a value that still doesn't exist?

On Multi-threading if I have multiple threads trying to access a single value I have a race condition. What is the name given if the condition is that I'm trying to ...
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concurrency vs parallelism

I am so confused between concurrency vs parallelism in multi-core processors. If a concurrent process has many threads and if the processor is multi-core then can each thread run on multiple cores? If ...
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48 views

concurrency in multiple core

I know the basic definition between parallelism and concurrency. But there is not much information about concurrency in multiple core. what is the difference between concurrency in single-core vs ...
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1answer
37 views

Running an application that needs 6 threads on dual core processor

If a dual core processor have 4 threads, then what will happen if i run an application which uses more than 4 threads? And just to make sure i'm understanding what are threads in a cpu, when an ...
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1answer
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Analyzing parallel performance question

I was reviewing for my CS class and came across this question and answer combo that didn't have any explanation why it was correct. I'm confused on how they got the answer: We have a system to which ...
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2answers
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How could i create a multi-threading system in a kernel?

Im trying to figure out if there's an assembler instructions or a bios intruction to get multi-threading in a kernel. In the case that doesn't exist that, how could i set muti-threading in a kernel?
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75 views

OS: Are User-level threads and software threads (and also kernel-level threads and hardware threads) the same?

I am referencing the Book Fundamentals of Computer Algorithms" by Ellis Horowitz et al. At the part which they talk about multi-threading models, user-level and kernel-level thread are introduced....
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How the task is divided between multiple cores to perform in multiprocessing systems?

I am trying to find how single task is divided between two cores? what are the methods makes them work at the same time without interfering with each other?
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Python 3 multiprocessing stacktrace CUDA failure?

I am working on a data processing script and trying to use multiprocessing so that it runs faster. Whenever I run the python script, I get the following error: 2020-12-24 18:30:22.679414457 [E:...
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How to enforce synchronization with two semaphores

Assume I have 4 threads, A B C D respectively. A finishes before B starts. B finishes before C or D start. How should I initial values and synchronize threads with 2 semaphores?
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Why do OS locks require hardware support?

I just read the chapter on locks in the book Operating Systems: Three Easy Pieces, and it discusses an implementation of locks (see in Figure 28.9) that involves a test-and-set hardware instruction. ...
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1answer
41 views

Why is it not a good idea to branch a thread outside of a parallel region while other threads are still executing?

Say I have $n$ threads executing in a parallel region and one of them leaves the parallel region when others are still continuing to execute in the parallel region. Why this is a $BAD$ idea? For ...
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Can User Level Thread read/write Kernel thread?

As far as I read in a OS text book (Operating Systems by Silberschatz) Kernel mode is for privileged task, so it it true to claim that "User Level Thread can read/write Kernel threads" ? ...
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1answer
110 views

Does every thread have its main function?

Does every thread have its own main function? I know that its have its own stack, but what about main function (not necessarily a function which called main). For example, when creating a thread, we ...
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What are the differences between Earliest Deadline First (EDF) and Earliest Due Date (EDD)?

From my understanding, the EDF (Earliest Deadline First) rule is essentially an iterative "version" of the EDD (Earliest Due Date) rule, which allows for preemption. At every point in time, ...
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1answer
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How to trigger a thread to start working using semaphore?

How to trigger a thread to start working using semaphore? I have find a lot of explanation about thread and semaphore but i still don't understand, any help please
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1answer
45 views

Thread - contention vs race

The terms contention and race are used interchangeably when it comes to thread's state(at critical section). Are they same?
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parallelized data structure

I'm searching a data structure that supports O(1) concurrent insertions (thread number is known in advance) and iteration over its elements (insertion order doesn't need to be preserved). While one ...
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2answers
214 views

Why the most dominant programming languages didn't follow CSP thread model?

I was trying to ask this question in StackOverflow, but later realized that this question is more relevant to general computer science, not specific engineering problems. If you think it's not, please ...
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1answer
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How does a dual core microprocessors run so many programs?

I have a laptop with Intel dual core and it runs, the OS windows, and many application from Opera, age of empires, word, excel etc open at once just fine. If it only has 2 cores, how can so many ...
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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
48 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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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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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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1answer
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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
38 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 ...
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1answer
486 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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276 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
1k 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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111 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
57 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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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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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
47 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
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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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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 . ...
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1answer
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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
159 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
225 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
154 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
23 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
217 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
4k 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
181 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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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 ...
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1answer
532 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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157 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
96 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 ...