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

[David Tellenbach <david.tellenbach@xxxxxx>]

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 <ztdepyahoo@xxxxxxxxx> 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);

	ztdepyahoo
ztdepyahoo@xxxxxxxxx

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