基础知识-Tensor

1、tensor.item() 用于得到 tensor的元素值

# coding:utf-8
import torch
import math
"""
    测试-torch  Tensor使用
"""
dtype = torch.float
device = torch.device("cpu")
x = torch.linspace(-math.pi, math.pi, 2000, device=device, dtype=dtype)
y = torch.sin(x)
a = torch.randn((), device=device, dtype=dtype)
b = torch.randn((), device=device, dtype=dtype)
c = torch.randn((), device=device, dtype=dtype)
d = torch.randn((), device=device, dtype=dtype)
learning_rate = 1e-6
for t in range(2000):
    y_pred = a+b*x+c*x**2+d*x**3
    loss = (y_pred - y).pow(2).sum().item()
    if t % 100 == 99:
        print(t, loss)
    grad_y_pred = 2.0 * (y_pred-y)
    grad_a = grad_y_pred.sum()
    grad_b = (grad_y_pred * x).sum()
    grad_c = (grad_y_pred * x ** 2).sum()
    grad_d = (grad_y_pred * x ** 3).sum()
    a -= learning_rate * grad_a
    b -= learning_rate * grad_b
    c -= learning_rate * grad_c
    d -= learning_rate * grad_d
print(f"Result : y ={a.item()}+{b.item()}x+{c.item()}x^2+{d.item()}x^3")