parallel-for | 易学教程

Efficient parallelization of operations on two dimensional array operations in python

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问题 I'm trying to parallelize operations on two dimensional array using joblib library in python. Here is the code I have from joblib import Parallel, delayed import multiprocessing import numpy as np # The code below just aggregates the base_array to form a new two dimensional array base_array = np.ones((2**12, 2**12), dtype=np.uint8) def compute_average(i, j): return np.uint8(np.mean(base_array[i*4: (i+1)*4, j*4: (j+1)*4])) num_cores = multiprocessing.cpu_count() new_array = np.array(Parallel(n

c++ ppl.h for parallel_for in linux [duplicate]

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问题 This question already has answers here : Alternatives to ppl (4 answers) Closed 10 months ago . I made project in windows using c++ and now I am trying to build my project in linux(ubunt). However, I couldn't find ppl.h in linux. I used a lot of parallel_for in my project. What is the replacement can I use? 回答1: Parallel Patterns Library is Windows only. It is not useful for portable application, it is considered that OpenMP is best alternative for PPL. I.e. for the parallel for you can use

Task.Factory.StartNew or Parallel.ForEach for many long-running tasks? [duplicate]

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问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Parallel.ForEach vs Task.Factory.StartNew I need to run about 1,000 tasks in a ThreadPool on a nightly basis (the number may grow in the future). Each task is performing a long running operation (reading data from a web service) and is not CPU intensive . Async I/O is not an option for this particular use case. Given an IList<string> of parameters, I need to DoSomething(string x) . I am trying to pick between

Does powershell's parallel foreach use at most 5 thread?

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问题 The throttlelimit parameter of foreach -parallel can control how many processes are used when executing the script. But I can't have more than 5 processes even if I set throttlelimit greater than 5. The script is executed in multiple powershell processes. So I check PID inside the script. And then group the PIDs so that I can know how many processes are used to execute the script. function GetPID() { $PID } workflow TestWorkflow { param($throttlelimit) foreach -parallel -throttlelimit

OpenMP parallel for with floating-point range

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问题 I have the following program: int main(){ double sum=0; #pragma omp parallel for reduction(+:sum) for(double x=0;x<10;x+=0.1) sum+=x*x; } When I compile it, I get the error invalid type for iteration variable ‘x’ . I take this to mean that I can only apply a parallel for construct to integer-based loops. But the internals of my loop really do depend on it being floating-point. Is there a way to convince OpenMP to do this? Is there a recommended alternative method? 回答1: From comments: No,

Does Thread.Sleep hinder other threads?

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问题 Here is a console program want 10 threads start in batch, wait 5 seconds, and stop in batch. static void Main(string[] args) { System.Threading.Tasks.Parallel.For(0, 10, (index) => { Action<int> act = (i) => { Console.Write("start {0} ", i); Thread.Sleep(5000); }; act.BeginInvoke(index, OnTaskComplete, index); }); Console.ReadKey(); } static void OnTaskComplete(IAsyncResult res) { Console.Write("finish {0} ", res.AsyncState); } but the result is not what I expected, 10 threads start one-by

tbb parallel_for example c++ without lambda

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Can you give me an example on tbb "parallel_for" without using lambda expression? Because I can't run lambda expression under Ubuntu system's C++ compiler, and I don't why. to be brief: turn this for loop into parallel_for please. void print(int n) { cout<<n<<endl; } for(int i=0; i<100; i++) { print(i); } by the way, if who can tell me how to run C++ lambda expression in linux system, that would be better for me. Thanks. parallel_for will take any functor, which can be a lambda, a functor class or a plain old function; the following should work just fine too: #include "tbb/tbb.h" using