Question

我想使用Eigen的张量类。我已经安装了Eigen 3.3.3，并确保我的项目选择了正确的版本（而不是旧的ubuntu软件包）

cout<<EIGEN_WORLD_VERSION<<"."<<EIGEN_MAJOR_VERSION<<"."<<EIGEN_MINOR_VERSION<<endl;

// prints 3.3.3

此代码有效：

Tensor<double, 3> t(3,3,3);
t.setConstant(1);

但是这段代码失败了：

t*=5;

错误消息抱怨int类型：

[ 50%] Building CXX object CMakeFiles/sandbox.dir/src/SandBox/sandbox.cpp.o
In file included from /opt/eigen333/include/eigen3/unsupported/Eigen/CXX11/Tensor:103:0,
                 from /home/lars/programming/fsd_cpp/src/SandBox/sandbox.cpp:3:
/opt/eigen333/include/eigen3/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h: In instantiation of ‘Derived& Eigen::TensorBase<Derived, AccessLevel>::operator*=(const OtherDerived&) [with OtherDerived = int; Derived = Eigen::Tensor<double, 3>; int AccessLevel = 1]’:
/home/lars/programming/fsd_cpp/src/SandBox/sandbox.cpp:30:6:   required from here
/opt/eigen333/include/eigen3/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h:876:36: error: request for member ‘derived’ in ‘other’, which is of non-class type ‘const int’
       return derived() = derived() * other.derived();

我已尝试t*=5.;，但只会将错误消息更改为which is of non-class type ‘const double’

当我将代码更改为：

时

t=t*5;

错误消息变得很长：https://pastebin.com/T6kvLaZ9

最终版本：

t=t*5.;

令人惊讶的是，这很有效。我不明白为什么t*=5.;会产生错误。

Answer 1

如上所述，本征张量当前不支持使用*运算符进行标量乘法。然而，逐元素张量乘法是。要对张量进行标量乘法，请使用命令t.constant(Scalar)创建尺寸与t相同但所有元素等于Scalar值的张量，只要Scalar是类型float。然后使用*运算符乘以该张量：

Tensor<double, 3> t(5,5);
t.setConstant(1);

Tensor<double, 3> ans(5,5) = t*t.constant(5.);
std::cout << t << std::endl;
std::endl;
std::cout << ans << std::endl;

产生

Answer 2

据我所知，当前的Eigen Tensor实现不支持标量乘法。但您可以尝试将Tensor转换为Matrix。

特征：张量乘法运算符的奇怪行为

2 个答案: