diff options
Diffstat (limited to 'unsupported/Eigen/CXX11/src/Tensor/README.md')
| -rw-r--r-- | unsupported/Eigen/CXX11/src/Tensor/README.md | 83 |
1 files changed, 71 insertions, 12 deletions
diff --git a/unsupported/Eigen/CXX11/src/Tensor/README.md b/unsupported/Eigen/CXX11/src/Tensor/README.md index 38cdb9c69..30d553af7 100644 --- a/unsupported/Eigen/CXX11/src/Tensor/README.md +++ b/unsupported/Eigen/CXX11/src/Tensor/README.md @@ -83,8 +83,8 @@ large enough to hold all the data. // You can also map fixed-size tensors. Here we get a 1d view of // the 2d fixed-size tensor. - Tensor<float, Sizes<4, 5>> t_4x3; - TensorMap<Tensor<float, 1>> t_12(t_4x3, 12); + TensorFixedSize<float, Sizes<4, 5>> t_4x3; + TensorMap<Tensor<float, 1>> t_12(t_4x3.data(), 12); #### Class TensorRef @@ -272,7 +272,7 @@ Operation to a TensorFixedSize instead of a Tensor, which is a bit more efficient. // We know that the result is a 4x4x2 tensor! - TensorFixedSize<float, 4, 4, 2> result = t5; + TensorFixedSize<float, Sizes<4, 4, 2>> result = t5; Simiarly, assigning an expression to a TensorMap causes its evaluation. Like tensors of type TensorFixedSize, TensorMaps cannot be resized so they have to @@ -296,7 +296,7 @@ the expression in a temporary Tensor of the right size. The code above in effect does: // .eval() knows the size! - TensorFixedSize<float, 4, 4, 2> tmp = t1 + t2; + TensorFixedSize<float, Sizes<4, 4, 2>> tmp = t1 + t2; Tensor<float, 3> result = (tmp * 0.2f).exp(); Note that the return value of ```eval()``` is itself an Operation, so the @@ -567,11 +567,11 @@ to the rank of the tensor. The content of the tensor is not initialized. ### TensorFixedSize -Creates a tensor of the specified size. The number of arguments in the Size<> +Creates a tensor of the specified size. The number of arguments in the Sizes<> template parameter determines the rank of the tensor. The content of the tensor is not initialized. - Eigen::TensorFixedSize<float, Size<3, 4>> a; + Eigen::TensorFixedSize<float, Sizes<3, 4>> a; cout << "Rank: " << a.rank() << endl; => Rank: 2 cout << "NumRows: " << a.dimension(0) << " NumCols: " << a.dimension(1) << endl; @@ -584,11 +584,11 @@ until the TensorMap is discarded, and the size of the data must be large enough to accomodate of the coefficients of the tensor. float data[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}; - Eigen::TensorMap<float, 2> a(data, 3, 4); + Eigen::TensorMap<Tensor<float, 2>> a(data, 3, 4); cout << "NumRows: " << a.dimension(0) << " NumCols: " << a.dimension(1) << endl; => NumRows: 3 NumCols: 4 cout << "a(1, 2): " << a(1, 2) << endl; - => a(1, 2): 9 + => a(1, 2): 7 ## Contents Initialization @@ -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 @@ -1168,6 +1175,58 @@ Reduce a tensor using a user-defined reduction operator. See ```SumReducer``` in TensorFunctors.h for information on how to implement a reduction operator. +## Trace + +A *Trace* operation returns a tensor with fewer dimensions than the original +tensor. It returns a tensor whose elements are the sum of the elements of the +original tensor along the main diagonal for a list of specified dimensions, the +"trace dimensions". Similar to the ```Reduction Dimensions```, the trace dimensions +are passed as an input parameter to the operation, are of type ```<TensorType>::Dimensions``` +, and have the same requirements when passed as an input parameter. In addition, +the trace dimensions must have the same size. + +Example: Trace along 2 dimensions. + + // Create a tensor of 3 dimensions + Eigen::Tensor<int, 3> a(2, 2, 3); + a.setValues({{{1, 2, 3}, {4, 5, 6}}, {{7, 8, 9}, {10, 11, 12}}}); + // Specify the dimensions along which the trace will be computed. + // In this example, the trace can only be computed along the dimensions + // with indices 0 and 1 + Eigen::array<int, 2> dims({0, 1}); + // The output tensor contains all but the trace dimensions. + Tensor<int, 1> a_trace = a.trace(dims); + cout << "a_trace:" << endl; + cout << a_trace << endl; + => + a_trace: + 11 + 13 + 15 + + +### <Operation> trace(const Dimensions& new_dims) +### <Operation> trace() + +As a special case, if no parameter is passed to the operation, trace is computed +along *all* dimensions of the input tensor. + +Example: Trace along all dimensions. + + // Create a tensor of 3 dimensions, with all dimensions having the same size. + Eigen::Tensor<int, 3> a(3, 3, 3); + a.setValues({{{1, 2, 3}, {4, 5, 6}, {7, 8, 9}}, + {{10, 11, 12}, {13, 14, 15}, {16, 17, 18}}, + {{19, 20, 21}, {22, 23, 24}, {25, 26, 27}}}); + // Result is a zero dimension tensor + Tensor<int, 0> a_trace = a.trace(); + cout<<"a_trace:"<<endl; + cout<<a_trace<<endl; + => + a_trace: + 42 + + ## Scan Operations A *Scan* operation returns a tensor with the same dimensions as the original @@ -1314,7 +1373,7 @@ The previous example can be rewritten as follow: Eigen::Tensor<float, 2, Eigen::ColMajor> a(2, 3); a.setValues({{0.0f, 100.0f, 200.0f}, {300.0f, 400.0f, 500.0f}}); Eigen::array<Eigen::DenseIndex, 2> two_dim({2, 3}); - Eigen::Tensor<float, 1, Eigen::ColMajor> b; + Eigen::Tensor<float, 1, Eigen::ColMajor> b(6); b.reshape(two_dim) = a; cout << "b" << endl << b << endl; => |