OpenFOAM libtorch tutorial step by step

[李东岳]

@chengan-wang 太老了，gcc版本啥的都太低了，我没有折腾过，你得亲自自己都尝试一下看看哪个能用

[chengan.wang]

@李东岳 李老师，http://dyfluid.com/pinn.html ，#include "output.H"这个文件能补充上传么，想研究一下您的完整代码，谢谢

[李东岳]

@chengan-wang 那个我已经删了，你可以参考这个写个类似的，纯粹是C++的输出数据：

        if (iter % 500 == 0) 
        {
            cout<< iter << " loss = " << loss.item<double>() << endl;

            auto meshxy = torch::cat({mesh,x,y}, 1);
            std::ofstream filex("results");
            filex << meshxy << "\n";
            filex.close();
        }

http://dyfluid.com/pinn2.html

[李东岳]

我给你手写了一个output.H：

        if (iter % 500 == 0) 
        {
            cout<< iter << " loss = " << loss.item<double>() << endl;
 
            std::ofstream filex("results");
            filex << upred << "\n";
            filex.close();
        }

[chengan.wang]

@李东岳 谢谢李老师

[chengan.wang]

@李东岳 我看了您提供的PINN算例，感觉目前还没有真正跟of结合起来，是吧？只不过用了of的c++编译环境，可以这么理解么？

[李东岳]

是。PINN不需要跟FVM结合，只不过用了of的c++编译环境。想跟OpenFOAM结合，除了画网格能结合一下，其他的也结合不上。

[李东岳]

@chengan-wang

You can use the following code to initialize libtorch tensors from OpenFOAM mesh. It is much easier to generate any kinds of geometries. Please see the following clipped cavity geometry. I am using English since I hope it can be helpful for all the people.

    // openfoam initialization
    vectorField ofMesh = mesh.C();
    auto meshTorch = torch::full({ofMesh.size(),1,2}, 0.0);
    forAll(ofMesh, i)
    {
        double x = ofMesh[i].x();
        double y = ofMesh[i].y();
        auto posi = torch::tensor({x,y}).reshape({1,2});
        meshTorch[i] = posi;
    }

    const surfaceVectorField& Cf = mesh.Cf(); 
    label topID = mesh.boundaryMesh().findPatchID("top");
    label leftID = mesh.boundaryMesh().findPatchID("left");
    label rightID = mesh.boundaryMesh().findPatchID("right");
    label bottomID = mesh.boundaryMesh().findPatchID("bottom");
    vectorField cfTop = Cf.boundaryField()[topID];
    vectorField cfLeft = Cf.boundaryField()[leftID];
    vectorField cfRight = Cf.boundaryField()[rightID];
    vectorField cfBottom = Cf.boundaryField()[bottomID];

    auto top = torch::full({cfTop.size(),1,2}, 0.0);
    auto left = torch::full({cfLeft.size(),1,2}, 0.0);
    auto right = torch::full({cfRight.size(),1,2}, 0.0);
    auto bottom = torch::full({cfBottom.size(),1,2}, 0.0);

    forAll(cfTop, i)
    {
        double x = cfTop[i].x();
        double y = cfTop[i].y();
        auto posi = torch::tensor({x,y}).reshape({1,2});
        top[i] = posi;
    }

    forAll(cfRight, i)
    {
        double x = cfRight[i].x();
        double y = cfRight[i].y();
        auto posi = torch::tensor({x,y}).reshape({1,2});
        right[i] = posi;
    }

    forAll(cfLeft, i)
    {
        double x = cfLeft[i].x();
        double y = cfLeft[i].y();
        auto posi = torch::tensor({x,y}).reshape({1,2});
        left[i] = posi;
    }

    forAll(cfBottom, i)
    {
        double x = cfBottom[i].x();
        double y = cfBottom[i].y();
        auto posi = torch::tensor({x,y}).reshape({1,2});
        bottom[i] = posi;
    }

    meshTorch = meshTorch.reshape({-1,2});
    top = top.reshape({-1,2});
    left = left.reshape({-1,2});
    right = right.reshape({-1,2});
    bottom = bottom.reshape({-1,2});

    auto u_top = torch::full({cfTop.size()}, vel);
    auto v_top = torch::full({cfTop.size()}, 0.0);

    std::cout<< "top: " << top << std::endl;
    std::cout<< "left: " << left << std::endl;
    std::cout<< "right: " << right << std::endl;
    std::cout<< "bottom: " << bottom << std::endl;