Re: [eigen] help: eigen3.3 desn't imporve the speed with multitreading.

Thu, 10 Sep 2020 17:35:10 -0700

sory for that. the "return 1" is my first question, i have solved it.
regards
On 9/11/2020 01:20，David Tellenbach<[email protected]> wrote：
Hi,

Sorry, I'm a bit confused:

I have set the tread =12 in the program .  Eigen::nbThreads( ) also feedbacks correct number. 

So Eigen::nbThreads() returns the correct number of threads but in your code snippet you say

     std::cout << "THREADS = " << nthreads <<std::ends; // returns '1'

What's the case?

Thanks,
David

On 10. Sep 2020, at 06:24, ztdepyahoo <[email protected]> wrote:

I have set the tread =12 in the program .  Eigen::nbThreads( ) also feedbacks correct number. 
but the speed of solution seems doesn't change. 
what is the reason.
Regards



    Eigen::setNbThreads(12);
     int nthreads = Eigen::nbThreads( );
     std::cout << "THREADS = " << nthreads <<std::ends; // returns '1'
    BiCGSTAB<SparseMatrix<double, RowMajor>, IncompleteLUT<double>> solver;
    solver.setTolerance(1e-10);
    solver.setMaxIterations(1000);
    solver.compute(A);
    VectorXd x = solver.solve(b);


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