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| #include <Eigen/Dense>
#include <unsupported/Eigen/CXX11/Tensor>
#include <iostream>
int main()
{
// 定义一个三维 Tensor，并赋值
Eigen::Tensor<double, 3> fs;
fs.resize(3, 3, 3);
int tempi = 0;
for (int i = 0; i < fs.dimension(0); i++)
{
for (int j = 0; j < fs.dimension(1); j++)
{
for (int k = 0; k < fs.dimension(2); k++)
{
fs(i, j, k) = 1.0 * tempi;
tempi++;
}
}
}
// 打印出 Tensor 的内容
std::cout << "fs:\n"
<< fs(0, 0, 0) << " " << fs(0, 0, 1) << " " << fs(0, 0, 2) << "\n"
<< fs(0, 1, 0) << " " << fs(0, 1, 1) << " " << fs(0, 1, 2) << "\n"
<< fs(0, 2, 0) << " " << fs(0, 2, 1) << " " << fs(0, 2, 2) << "\n\n"
<< fs(1, 0, 0) << " " << fs(1, 0, 1) << " " << fs(1, 0, 2) << "\n"
<< fs(1, 1, 0) << " " << fs(1, 1, 1) << " " << fs(1, 1, 2) << "\n"
<< fs(1, 2, 0) << " " << fs(1, 2, 1) << " " << fs(1, 2, 2) << "\n\n"
<< fs(2, 0, 0) << " " << fs(2, 0, 1) << " " << fs(2, 0, 2) << "\n"
<< fs(2, 1, 0) << " " << fs(2, 1, 1) << " " << fs(2, 1, 2) << "\n"
<< fs(2, 2, 0) << " " << fs(2, 2, 1) << " " << fs(2, 2, 2) << std::endl;
// 做切片，以下代码保留 Tensor 的第三层，即 fs(2, :, :)
int off0 = 2;
int off1 = 0;
int off2 = 0;
int w0 = 1;
int w1 = fs.dimension(1);
int w2 = fs.dimension(2);
Eigen::array<Eigen::Index, 3> offsets = {off0, off1, off2};
Eigen::array<Eigen::Index, 3> extents = {w0, w1, w2};
Eigen::Tensor<double, 3> fs_slice = fs.slice(offsets, extents); // 提取第 3 层（从第 6 行开始，3x3 矩阵）
std::cout << "fs.slice({" << off0 << ", " << off1 << ", " << off2
<< "}, {" << w0 << ", " << w1 << ", " << w2 << "}):\n";
for (int i = 0; i < fs_slice.dimension(0); i++)
{
for (int j = 0; j < fs_slice.dimension(1); j++)
{
for (int k = 0; k < fs_slice.dimension(2); k++)
{
std::cout << fs_slice(i, j, k) << " ";
}
std::cout << "\n"
<< std::endl;
}
std::cout << "\n"
<< std::endl;
}
// chip(m,n): 返回一个低一维度的 Tensor，返回第 n 个维度上的第 m 个 Tensor 切片
// 这里返回的 fs_slice 就是 fs_slice_2d(:,:) = fs(0, :, :)
Eigen::Tensor<double, 2> fs_slice_2d = fs_slice.chip(0, 0);
std::cout << "fs_slice_2d:\n"
<< fs_slice_2d << std::endl;
Eigen::MatrixXd matrix2d = Eigen::Map<const Eigen::Matrix<double, 3, 3>>(fs_slice_2d.data());
std::cout << "matrix2d:\n"
<< matrix2d << std::endl;
// 定义标量 psio
double psio = 2;
// 定义结果矩阵 jac
Eigen::MatrixXd jac(3, 3);
// 执行逐元素除法操作
jac.array() = matrix2d.array() / psio;
// 打印结果矩阵 jac
std::cout << "Matrix jac:\n"
<< jac << std::endl;
return 0;
|
