CODEWITHSUNDEEP
eigenmultiplicationeigen3tensor
Brans Ds
Brans Ds

Reputation: 4117

How to multiple two Eigen tensors along batch dimension?

For example, I have a tensor A(2,3,4) and tensor B(3,4) and want to make koefs multiplication(not Contraction operation) of A along dimension 0( batch dimension) with B. How to do this without for loop?

Upvotes: 0

Views: 1105

Answers (1)

florestan
florestan

Reputation: 4655

If I understand your question, you could first reshape B to (1,3,4) and then use broadcasting to replicate the values along axis 0. Don't know if this is very efficient, but it works.

auto A = Tensor<float, 3>(2, 3, 4);
A.setValues({
    {
        {1,2,3,4},
        {5,6,7,8},
        {9,10,11,12},
    },{
        { 10,20,30,40 },
        { 50,60,70,80 },
        { 90,100,110,120 },
    }
});

auto W = Tensor<float, 2>(3,4);
W.setValues({ 
    { 1,2,3,4 },
    { 5,6,7,8 },
    { 9,10,11,12 }
});


auto three_dims = Eigen::array<int, 3>({ 1,3,4 });
auto bcast = Eigen::array<int, 3>({ 2,1,1 });
auto X = W.reshape(three_dims).broadcast(bcast);

auto Y = A*X;

std::cout << Y << std::endl;

Prints:

 1   25   81    4   36  100    9   49  121   16   64  144
 10  250  810   40  360 1000   90  490 1210  160  640 1440

Upvotes: 2

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