I need to perform some basic numerical integrations in pytorch and am currently investigating feasible methods. As a validity check for using the new torch.trapz function, I implemented the Matlab example on multiple numerical integration 3:
import torch

dx = 0.1
x = torch.arange(-3, 3, dx)
y = torch.arange(-5, 5, dx)
X, Y = torch.meshgrid(x, y)

F = X**2 + Y**2

result = torch.trapz(torch.trapz(F, dx=dx, dim=0), dx=dx, dim=0)
# Returns tensor(646.9882)

The result is quite far away from what Matlab produces (680.200) and the exact value of 680. Is this expected? If yes, why so?
What would be a simple alternative to using torch.trapz?