Plot derivatives of sin(x) using pytorch

user_531886 0
Viewed 85

Am unsure why my code does not plot cos(x) (yes, am aware pytorch has cos(x) function)

import math
import os
import torch
import numpy as np
import matplotlib.pyplot as plt
import random

x = torch.linspace(-math.pi, math.pi, 5000, requires_grad=True)
y = torch.sin(x)
y.backward(x)
x.grad == torch.cos(x) # assert x.grad same as cos(x)
plt.plot(x.detach().numpy(), y.detach().numpy(), label='sin(x)')
plt.plot(x.detach().numpy(), x.grad.detach().numpy(), label='cos(x)') # print derivative of sin(x)
autograd pytorch
1 Answers

You need to feed the upstream gradient (equals to all ones in your case) instead of x as input to y.backward().

Thus

import math
import torch
import matplotlib.pyplot as plt

x = torch.linspace(-math.pi, math.pi, 5000, requires_grad=True)
y = torch.sin(x)
y.backward(torch.ones_like(x))
plt.plot(x.detach().numpy(), y.detach().numpy(), label='sin(x)')
plt.plot(x.detach().numpy(), x.grad.detach().numpy(), label='cos(x)') # print derivative of sin(x)
plt.show()
user_32374380
Related