Hello,

Running the follow code I get different convolution results for a single image and filter between scipy convolve2d and torch.nn.functional.conv2d().

The filter is size 3 thus a padding size of (1,1) should be correct regardless.

Why does this difference occur?

```
import numpy as np
import torch
import scipy
from torch.nn import functional as F
from scipy import signal
imgSize = 5
testImg = np.array([[1.0, 2, 3, 4, 5], [4, 5, 6, 7, 8], [7, 8, 9, 10, 11], [11, 12, 13, 14, 15], [16, 17, 18, 19, 20]])
testFilt = np.array([[1, 2, 5], [3.0, 4, 2], [7, 8, 9]])
# Numpy test
npConv = scipy.signal.convolve2d(testImg, testFilt, mode='same')
filt = torch.from_numpy(testFilt).type(torch.float32)
filt = filt.unsqueeze(0).unsqueeze(0)
img = torch.from_numpy(testImg).type(torch.float32)
img = img.unsqueeze(0).unsqueeze(0)
# Padding pads on both sides symmetrically
# Doesn't match scipy?
funOut = F.conv2d(img, filt, bias=None, padding=1, stride=(1, 1))
print(npConv)
print(funOut)
```