Reshape cannot be used when handling tensors in Eigen

Error when using the tensor calculation part of "unsupported" in C++'s linear algebra library Eigen.

https://qiita.com/suzuryo3893/items/1a79b4e9410f1803b4fa#geometrica...

as in

// Increased tensor rank with introduction of a new dimension of size 1
Tensor<float,2>input(7,11);
array<int,3>three_dims {{7,11,1}};
Tensor<float,3>result=input.reshape(three_dims);

In an attempt to copy the description, I wrote the source code as follows:

#include "unsupported/Eigen/CXX11/Tensor"
using namespace Eigen;

int main() {
　Tensor<float,2>input(7,11);
　Eigen::array<int,3>three_dims {{7,11,1}}};
　Tensor<float,3>result=input.reshape(three_dims);
　return 0;
}

My PC is mac (Mojave) and I compiled it as follows:

g++-std=c++14-I(path to Eigen) eigen_practice.cpp-oeigen_practice

However, I get the following error:

 error:
no matching member function for call to 'resize'
(omitted)
candidate function not visible:requires 0 arguments, but 1 was provided
void resize()
^
1 error generated.

Is there something missing to include?

Also, why is the function "resize" asked when it should be called "reshape"?

This is a poor explanation, but I will supplement it accordingly.
Thank you for your cooperation.

Here is the full error statement:

Infile included from eigen_practice.cpp:12:
File included from /Users/yamamoto/Dropbox/include_for_C++/eigen/unsupported/Eigen/CXX11/Tensor: 145:
/Users/yamamoto/Dropbox/include_for_C++/eigen/unsupported/Eigen/CXX11/src/Tensor/Tensor.h:397:7: error: 
      no matching member function for call to 'resize'
      resize (TensorEvaluator <const Assign,DefaultDevice > (assign,Default...)
      ^~~~~~
eigen_practice.cpp:63:28:note:instantiation of function template
      specialization'Eigen::Tensor<float,3,0,
      long>::Tensor<Eigen::TensorReshapingOp<conststd::__1::array<int,3>,
      Eigen::Tensor<float,2,0,long>>'requested here
        Tensor<float,3>result=input.reshape(three_dims);
                                  ^
/Users/yamamoto/Dropbox/include_for_C++/eigen/unsupported/Eigen/CXX11/src/Tensor/Tensor.h:423:10:note: 
      candidate function template not visible: no known conversion from 'const
      Eigen::TensorEvaluator<const Eigen::TensorAssignOp<Eigen::Tensor<float, 3,
      0, long>, const Eigen::TensorReshapingOp<conststd::__1::array<int,3>,
      Eigen::Tensor<float, 2,0, long>>>, Eigen::DefaultDevice>::Dimensions'
      (aka'const std::__1::array<int, 3>') to 'Eigen::Tensor<float, 3, 0,
      long>::Index'(aka'long') for 1st argument
    void resize (Index firstDimension, IndexTypes...otherDimension)
         ^
/Users/yamamoto/Dropbox/include_for_C++/eigen/unsupported/Eigen/CXX11/src/Tensor/Tensor.h:432:28:note: 
      candidate function not visible —no known conversion from
      'array<int,[...]>'to' const array<long,[...]>' for 1st argument
    EIGEN_DEVICE_FUNC void resize (constray <Index,NumIndices > & dimensions)
                           ^
/Users/yamamoto/Dropbox/include_for_C++/eigen/unsupported/Eigen/CXX11/src/Tensor/Tensor.h:450:28:note: 
      candidate function not visible —no known conversion from 'const
      Eigen::TensorEvaluator<const Eigen::TensorAssignOp<Eigen::Tensor<float, 3,
      0, long>, const Eigen::TensorReshapingOp<conststd::__1::array<int,3>,
      Eigen::Tensor<float, 2,0, long>>>, Eigen::DefaultDevice>::Dimensions'
      (aka'const std::__1::array<int, 3>') to'const
      DSizes<Eigen::Tensor<float,3,0,long>::Index,NumIndices>'(aka'const
      DSizes<long,NumIndices>') for 1st argument
    EIGEN_DEVICE_FUNC void resize (const DSizes <Index,NumIndices > & dimensions) {
                           ^
/Users/yamamoto/Dropbox/include_for_C++/eigen/unsupported/Eigen/CXX11/src/Tensor/Tensor.h:479:10:note: 
      candidate template ignored: could not match 'Sizes' against 'array'
    void resize (const Sizes <Indices...> & dimensions) {
         ^
/Users/yamamoto/Dropbox/include_for_C++/eigen/unsupported/Eigen/CXX11/src/Tensor/Tensor.h:459:10:note: 
      candidate function not visible:requires 0 arguments, but 1 was provided
    void resize()
         ^
1 error generated.

c++

2022-09-30 21:40

1 Answers

I'm sorry, but I was told that there is an answer at the following URL.
https://stackoverflow.com/questions/56985731/how-to-reshape-a-tensor-in-eigen3

The array that specifies the shape of the tensor must be an index of the tensor, not an integer type.
So

Eigen::array<int,3>three_dims {{7,11,1}};

Not

Eigen::array<Eigen::Index, 3>three_dims {{7,11,1}}};

It seemed necessary to write

2022-09-30 21:40

If you have any answers or tips

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