Hi, I tried searching everywhere, but I can’t seem to find a way to make it work for me, I have a code in which I have to optimize some parameters so I call the backward of the loss fucntion I’m using, but I always get None gradient for the last two parameters I’m trying to optimize. Now I thought that it could be due to the torch.tensor call I use to assemble the tensors, but I don’t know how to avoid it, can anyone help me sort out why this happens and how can I do to fix this?? Thanks a lot in advance. Following I post my code so that you can understand what I’m talking about

```
in_color = torch.tensor([0.5, 0.5, 0.5])
angle = torch.tensor(0.763965)
angle.requires_grad_(True)
in_color.requires_grad_(True)
params.append(angle)
params.append(in_color)
def check_hue(myHue):
if myHue < 0:
myHue = myHue + 360 * abs(myHue // 360)
elif myHue >= 360:
myHue = myHue - 360 * (myHue // 360)
return myHue
def HSLtoRGB(myColor):
with torch.no_grad():
myColor[0] = check_hue(myColor[0])
C = (1 - abs(2 * myColor[2] - 1)) * myColor[1]
X = C * (1 - abs((myColor[0].data / 60) % 2 - 1))
m = myColor[2] - C / 2
if 0 <= myColor[0] < 60:
myRGB = torch.tensor([C, X, 0]) + m
elif 60 <= myColor[0] < 120:
myRGB = torch.tensor([X, C, 0]) + m
elif 120 <= myColor[0] < 180:
myRGB = torch.tensor([0, C, X]) + m
elif 180 <= myColor[0] < 240:
myRGB = torch.tensor([0, X, C]) + m
elif 240 <= myColor[0] < 300:
myRGB = torch.tensor([X, 0, C]) + m
elif 300 <= myColor[0] < 360:
myRGB = torch.tensor([C, 0, X]) + m
return myRGB
def randomAngle(myColor, angle):
#myHSL = RGBtoHSL(myColor)
with torch.no_grad():
myColor[0] = myColor[0] * 360
percent = 0.1
HSL1 = torch.tensor([myColor[0] - angle * 360, myColor[1], myColor[2]])
HSL2 = torch.tensor([myColor[0] - angle * 180, myColor[1], myColor[2]])
HSL3 = myColor
HSL4 = torch.tensor([myColor[0] + angle * 180, myColor[1], myColor[2]])
HSL5 = torch.tensor([myColor[0] + angle * 360, myColor[1], myColor[2]])
with torch.no_grad():
c1 = HSLtoRGB(HSL1)
c2 = HSLtoRGB(HSL2)
c3 = HSLtoRGB(HSL3)
c4 = HSLtoRGB(HSL4)
c5 = HSLtoRGB(HSL5)
c1b = c1 * (1 - percent) + myColor * percent
c2b = c2 * (1 - percent) + myColor * percent
c3b = c3 * (1 - percent) + myColor * percent
c4b = c4 * (1 - percent) + myColor * percent
c5b = c5 * (1 - percent) + myColor * percent
# create vector of colors
colors = [c1b, c2b, c3b, c4b, c5b]
return colors
params[2] = randomAngle(params[-1], params[-2])[x[j]]
params[3] = randomAngle(params[-1], params[-2])[y[j][i]]
```

In this code I show the initialization of my parameters, then the “manipulation” of them and where I use them. The code is incomplete because is to long to be shown in its integrity, but I’m not touching my parameters elsewhere. The rest of the code is the same for every parameters (I have many others in the vector params, and for every of them I have a value of the gradient different than None, except for in_color and angle.