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Merged in tntnatbry/eigen (pull request PR-319)

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Tensor Trace op
This commit is contained in:
Benoit Steiner
2017-07-07 04:18:03 +00:00
parent 6795512e59
commit 9daed67952
7 changed files with 526 additions and 0 deletions
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52
unsupported/Eigen/CXX11/src/Tensor/README.md
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@@ -1168,6 +1168,58 @@ 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
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### <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