uc-modern-cpp-student/cc/tensor/tensor.h

#pragma once
#include <numeric>
#include <random>
#include <vector>
#include <memory>
#include <stdexcept>
#include <pybind11/pybind11.h>
#include <pybind11/numpy.h>

namespace py = pybind11;

namespace tensor {

class Tensor {
public:
    std::vector<float> data;
    std::vector<std::size_t> shape;
    std::size_t size;

public:
    Tensor(const std::vector<std::size_t>& shape, bool rand_init = false) 
    {
        this->size = std::accumulate(shape.begin(), shape.end(), static_cast<std::size_t>(1), std::multiplies<std::size_t>());
        this->data.resize(this->size);
        this->shape = shape;
        if (rand_init) {
            double limit = std::sqrt(3.0 / ((shape[0] + shape[1]) / 2.0));
            std::mt19937 gen(42);
            std::uniform_real_distribution<float> dis(-limit, limit);
            for (std::size_t i = 0; i < this->size; ++i) {
                this->data[i] = dis(gen);
            }
        }
    }
    Tensor(const std::vector<std::size_t>& shape, const std::vector<float>& data) 
     {
    // 计算总元素数（size）
    this->size = std::accumulate(shape.begin(), shape.end(), static_cast<std::size_t>(1), std::multiplies<std::size_t>());

    // 校验 data 长度是否与 shape 匹配
    if (data.size() != this->size) {
        throw std::runtime_error("Tensor 构造失败：data 长度与 shape 不匹配");
    }

    // 初始化成员变量
    this->shape = shape;
    this->data = data;  // 直接复制传入的 data
    }
    
    std::shared_ptr<Tensor> transpose();

    Tensor operator+(const Tensor& other) const {
        if (this->shape != other.shape) {
            throw std::runtime_error("Shapes do not match");
        }
        Tensor result(this->shape);
        for (std::size_t i = 0; i < this->size; ++i) {
            result.data[i] = this->data[i] + other.data[i];
        }
        return result;
    }

    Tensor operator=(const Tensor& other) const {
        if (this->shape != other.shape) {
            throw std::runtime_error("Shapes do not match");
        }
        Tensor result(this->shape);
        for (auto i = 0; i < this->size; i++) {
            result.data[i] = (this->data[i] == other.data[i]); 
        }
        return result;
    }

    std::vector<std::size_t> get_shape() const {
        return this->shape;
    }

    std::vector<float> get_data() const {
        return this->data;
    }

    float get(const std::vector<std::size_t>& indices) const {
        std::size_t index = 0;
        std::size_t stride = 1;
        for (int i = shape.size() - 1; i >= 0; i--) {
            index += indices[i] * stride;
            stride *= shape[i];
        }
        return data[index];
    }

    void set(const std::vector<std::size_t>& indices, float value) {
        std::size_t index = 0;
        std::size_t stride = 1;
        for (int i = shape.size() - 1; i >= 0; i--) {
            index += indices[i] * stride;
            stride *= shape[i];
        }
        data[index] = value;
    }
    ~Tensor() = default;
};  // class Tensor

std::shared_ptr<Tensor> pyarray_to_tensor(py::array_t<float> array);
std::shared_ptr<Tensor> argmax(const std::shared_ptr<Tensor>& tensor, int axis);
std::shared_ptr<Tensor> mean(const std::shared_ptr<Tensor>& tensor);
std::shared_ptr<Tensor> exp(const std::shared_ptr<Tensor>& tensor);
}  // namespace tensor