GitHub-Proxy/eigen
1
0
Fork 0
mirror of https://gitlab.com/libeigen/eigen.git synced 2025-08-11 19:29:02 +08:00
Code Issues Packages Projects Releases Wiki Activity

Added an example for a contraction to a scalar value, e.g. a double contraction of two second order tensors and how you can get the value of the result. I lost one day to get this doen so I think it will help some guys. I also added Eigen:: to the IndexPair and and array in the same example.

Browse Source
This commit is contained in:
Jonas Harsch 2017-09-01 11:30:26 +00:00
parent a4089991eb
commit a991c80365
1 changed files with 10 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
unsupported/Eigen/CXX11/src/Tensor/README.md
View File

@ -1016,13 +1016,20 @@ multidimensional case.
a.setValues({{1, 2}, {4, 5}, {5, 6}});
// Compute the traditional matrix product
array<IndexPair<int>, 1> product_dims = { IndexPair(1, 0) };
Eigen::array<Eigen::IndexPair<int>, 1> product_dims = { Eigen::IndexPair(1, 0) };
Eigen::Tensor<int, 2> AB = a.contract(b, product_dims);
// Compute the product of the transpose of the matrices
array<IndexPair<int>, 1> transpose_product_dims = { IndexPair(0, 1) };
Eigen::array<Eigen::IndexPair<int>, 1> transpose_product_dims = { Eigen::IndexPair(0, 1) };
Eigen::Tensor<int, 2> AtBt = a.contract(b, transposed_product_dims);
// Contraction to scalar value using a ouble contraction
// First coordinate of both tensors are contracted as well as both second coordinates
Eigen::array<Eigen::IndexPair<int>, 2> double_contraction_product_dims = { Eigen::IndexPair<int>(0, 0), Eigen::IndexPair<int>(1, 1) };
Eigen::Tensor<int, 0> AdoubleontractedA = a.contract(a, double_contraction_product_dims);
// Extracting the scalar value of the tensor contraction for further usage
int value = AdoublecontractedA(0);
## Reduction Operations