Hello, By using torch.autograd.set_detect_anomaly(True), Pytorch returns this error. I am using cnn in my code.
RuntimeError                              Traceback (most recent call last)
<ipython-input-64-d65b1c842b33> in <module>
     40 
     41         # Backward pass
---> 42       loss.backward()
     43         # Optimize the weights
     44       optimizer.step()

~\anaconda3\lib\site-packages\torch\tensor.py in backward(self, gradient, retain_graph, create_graph, inputs)
    243                 create_graph=create_graph,
    244                 inputs=inputs)
--> 245         torch.autograd.backward(self, gradient, retain_graph, create_graph, inputs=inputs)
    246 
    247     def register_hook(self, hook):

~\anaconda3\lib\site-packages\torch\autograd\__init__.py in backward(tensors, grad_tensors, retain_graph, create_graph, grad_variables, inputs)
    143         retain_graph = create_graph
    144 
--> 145     Variable._execution_engine.run_backward(
    146         tensors, grad_tensors_, retain_graph, create_graph, inputs,
    147         allow_unreachable=True, accumulate_grad=True)  # allow_unreachable flag

RuntimeError: Function 'AddmmBackward' returned nan values in its 2th output.


By using, print(model.fc1.weight.grad) in the code, the output I get is:
tensor([[[[ 1.0000e+00,  2.0121e+16,  2.1112e+03, -1.2587e+02,  1.1975e+02,  9.1882e+01,  1.4300e+02,  1.4685e+02,
            5.6806e+01,  6.2351e+01,  1.3990e+02,  1.0970e+02,  1.6538e+02,  1.3725e+02,  1.2693e+02,  2.7573e+01,
            1.1658e+02, -1.7453e+01,  5.7874e+01, -7.4747e+01,  5.4523e-01,  9.1882e+01, -5.6166e+01,  2.1318e+01,
            1.2021e+02, -1.5615e+02, -1.2587e+02, -1.2144e+02,  2.5129e+01,  1.1975e+02, -5.0621e+01, -1.0840e+02,
           -1.6882e+02, -1.2074e+02, -4.0773e+01,  1.0225e+02, -1.6588e+02, -4.7247e+01,  8.4561e+01,  1.7495e+02,
           -2.0543e+01,  1.4607e+02, -1.0414e+02, -4.2305e+01,  9.7643e+01, -1.5160e+02,  1.1463e+02, -4.9136e+01,
            2.0322e+01,  2.2924e+01,  4.8046e-01,  8.7566e-01,  5.6928e-01,  1.8828e+00,  2.6070e+00,  6.8450e-01,
            1.0887e+00,  8.5651e-01,  1.3067e+00,  9.8682e-01,  3.0889e+00,  2.0896e+01,  4.3667e+01,  1.0537e+00,
            1.1503e+00,  1.8539e+00,  1.3042e+01,  5.0504e-01,  5.6928e-01,  1.1076e+00,  1.8138e+00,  2.6676e+00,
                   nan,  4.8046e-01,  3.5797e-01,  7.3913e-01,  8.7566e-01,  1.4186e+00,  1.4761e+00,         nan,
            5.5842e-01,         nan,  8.8135e-01,         nan,  1.0344e+00,  1.1153e+00,  1.2731e+00,  5.4525e+00,
            2.7410e+00,  3.8250e+00,  1.9446e+01,  2.8108e+01,  5.8824e+01,  5.1819e+01,  4.9466e+01,  4.6651e+01]]]],
       dtype=torch.float64)
tensor([[0., 0., 0.,  ..., 0., 0., 0.],
        [0., 0., 0.,  ..., 0., 0., 0.],
        [-0., -0., -0.,  ..., -0., -0., -0.],
        ...,
        [0., 0., 0.,  ..., 0., 0., 0.],
        [0., 0., 0.,  ..., 0., 0., 0.],
        [-0., -0., -0.,  ..., -0., -0., -0.]])
tensor([[[[2.0000e+00, 2.0121e+16,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan]]]], dtype=torch.float64)
tensor([[nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        ...,
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan]])
tensor([[[[ 2.0000e+00,  2.0121e+16,  2.1799e+03, -1.2642e+02,  1.1888e+02,  9.2102e+01,  1.3392e+02,  1.5826e+02,
            5.6402e+01,  6.0114e+01,  1.3267e+02,  1.3073e+02,  1.6000e+02,  1.3671e+02,  1.3763e+02,  1.4622e+02,
            9.7603e+01, -2.1623e+01,  4.7637e+01, -1.0052e+02, -2.0893e+00,  9.2102e+01, -8.4090e+01,  3.2523e+00,
            1.1199e+02, -1.4152e+02, -1.2642e+02, -1.0328e+02,  2.2450e+01,  1.1888e+02, -5.3248e+01, -1.0527e+02,
           -1.3257e+02, -1.2736e+02, -5.6363e+01,  1.2717e+02, -1.3012e+02, -4.9418e+01,  9.6423e+01, -1.3353e+02,
           -2.4414e+01,  1.4379e+02, -1.0854e+02, -6.4658e+01,  9.7735e+01, -1.4628e+02, -7.0982e+01,  7.2506e+01,
           -6.3233e+01,  2.2006e+01,  4.1336e+00,  3.9871e+00,  3.7840e+00,  1.1910e+01,  7.4683e+00,  4.5036e+00,
            1.9909e+00,  1.1300e+01,  2.6995e+01,  8.0197e+00,  1.2381e+01,  2.6532e+01,  3.8079e+01,  5.4645e+01,
            4.8356e+00,  1.5947e+01,  1.0069e+02,  1.8042e+00,  3.7840e+00,  1.3642e+01,  4.0943e+00,  8.5131e+00,
            8.3134e+01,  4.1336e+00,  1.9227e+01,  4.8255e+00,  3.9871e+00,  9.3339e+00,  8.9132e+00,  1.0333e+02,
            5.4045e+00,  1.4110e+01,  2.7794e+01,  6.7948e+01,  1.5307e+01,  2.0399e+01,  1.0004e+02,  1.6973e+01,
            4.8058e+00,  1.2377e+01,  3.2879e+01,  1.1396e+02,  2.7245e+01,  5.0165e+01,  1.0444e+02,  1.4360e+02]]]],
       dtype=torch.float64)
tensor([[nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        ...,
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan]])
tensor([[[[ 2.0000e+00,  2.0121e+16,  2.1468e+03, -1.1650e+02,  1.0681e+02,  9.2336e+01,  1.6192e+02,  1.5636e+02,
            6.8639e+01,  6.9372e+01,  1.2871e+02,  1.2097e+02,  1.6926e+02,  9.7851e+01,  9.9558e+01,  1.6124e+02,
            1.0247e+02, -8.7555e+00,  7.4999e+01, -1.4355e+02, -4.5936e+00,  9.2336e+01, -6.6639e+01,  9.2131e+00,
            1.1063e+02, -1.6793e+02, -1.1650e+02, -1.0717e+02,  1.3600e+01,  1.0681e+02, -4.9655e+01, -1.1447e+02,
           -1.4637e+02, -1.1646e+02, -8.0738e+01,  1.3582e+02, -1.6939e+02, -8.9483e+01,  1.0139e+02, -1.6476e+02,
           -5.4197e+01,  6.2026e+01, -9.1667e+01, -6.2413e+01, -5.6123e+01, -7.2598e+01, -5.5944e+01, -4.4062e+01,
           -7.8543e+01,  1.9982e+01,  4.2698e+00,  6.2515e+00,  9.2737e-01,  8.4033e+00,  4.7989e+00,  5.4807e+00,
            4.5356e+00,  6.7761e+00,  6.4291e+00,  2.3736e+01,  3.4663e+01,  3.6859e+01,  1.9547e+01,  6.6953e+01,
            4.2942e+00,  8.7091e+00,  3.5222e+01,  3.6455e+00,  9.2737e-01,  1.5033e+01,  4.8080e+00,  4.2720e+00,
            3.4953e+01,  4.2698e+00,  7.1668e+00,  1.5076e+01,  6.2515e+00,  3.2291e+01,  1.2008e+01,  7.9383e+01,
            3.2539e+00,  1.8213e+01,  7.3228e+01,  1.9818e+01,  6.4666e+00,  1.1351e+02,  5.2506e+01,  4.9471e+01,
            1.2409e+02,  8.9141e+01,  8.0393e+01,  1.1634e+02,  1.1175e+02,  8.0143e+01,  1.2202e+02,  1.1002e+02]]]],
       dtype=torch.float64)
tensor([[nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        ...,
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan]])
tensor([[[[ 3.0000e+00,  2.0121e+16,  2.1307e+03, -1.1836e+02,  1.1960e+02,  9.3335e+01,  1.7614e+02,  1.6423e+02,
            6.0497e+01,  6.4295e+01,  1.4674e+02,  1.0307e+02,  1.3393e+02,  1.3606e+02,  8.8506e+01,  1.6990e+02,
           -6.3892e+01,  3.0301e+00,  9.6623e+01, -4.6353e+01,  3.2749e+00,  9.3335e+01, -3.5689e+01,  1.6018e+01,
            1.0254e+02, -1.6364e+02, -1.1836e+02, -1.1859e+02,  2.3843e+01,  1.1960e+02, -5.1990e+01, -1.3287e+02,
           -1.5137e+02, -1.2043e+02, -4.7107e+01,  1.1174e+02, -1.6050e+02, -9.1735e+01, -1.8729e+01, -1.6668e+02,
           -1.9044e+01,  1.4821e+02, -1.0359e+02, -8.7890e+01, -8.5127e+01, -1.3848e+02, -8.3747e+01, -8.5320e+01,
           -1.2180e+02,  2.6135e+01,  1.9769e+00,  2.6045e+00,  2.0390e+00,  1.4901e+00,  5.6421e+00,  3.7508e+00,
            3.1743e+00,  3.1110e+00,  1.0373e+01,  2.7232e+01,  7.2261e+00,  2.2325e+01,  2.9433e+01,  2.2821e+01,
            3.0788e+00,  2.6993e+00,  2.5304e+01,  2.2994e+00,  2.0390e+00,  1.1612e+01,  3.0532e+00,  6.5961e+00,
            5.8219e-01,  1.9769e+00,  1.8826e+00,  2.6724e+00,  2.6045e+00,  5.0856e+00,  2.8424e+00,  1.9730e+00,
            5.0156e-01,  1.5276e+01,  8.1453e+00,  4.4028e+00,  1.6706e+01,  1.3667e+02,  2.1477e+01,  1.6028e+01,
            8.0510e+00,  1.0984e+01,  7.1106e+01,  4.7512e+01,  8.9697e+01,  7.9041e+01,  4.4746e+01,  1.0752e+02]]]],
       dtype=torch.float64)
tensor([[nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        ...,
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan]])
tensor([[[[1.0000e+00, 2.0121e+16,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,        nan,
                  nan,        nan,        nan,        nan,        nan,        nan]]]], dtype=torch.float64)
tensor([[nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        ...,
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan]])
tensor([[[[ 3.0000e+00,  2.0121e+16,  2.1919e+03, -1.2222e+02,  1.2178e+02,  9.2645e+01,  1.4630e+02,  1.6849e+02,
            5.7381e+01,  5.9252e+01,  1.2452e+02,  1.6066e+02,  1.6036e+02,  1.3954e+02,  8.3678e+01,  1.6861e+02,
            9.9969e+01, -6.3340e+00,  5.9333e+01, -8.1033e+01,  3.7224e-01,  9.2645e+01, -8.6560e+01,  7.4431e-01,
            1.0392e+02,  1.5384e+02, -1.2222e+02, -8.0856e+01,  1.9358e+01,  1.2178e+02, -6.0104e+01, -1.1192e+02,
           -1.6483e+02, -1.2422e+02, -9.5145e+01, -1.2774e+02, -1.3558e+02, -7.7553e+01,  6.8804e+01, -1.4478e+02,
           -2.5068e+01,  1.4691e+02, -1.0733e+02,  4.9468e+01,  5.9000e+01, -1.4433e+01,  4.2396e+01,  5.9469e+01,
           -1.6240e+01,  2.1173e+01,  2.1348e+00,  4.0060e+00,  9.0399e-01,  1.3519e+01,  2.0945e+00,  2.4240e+00,
            4.3001e+00,  3.8076e+00,  1.4390e+01,  1.5359e+01,  5.6460e+00,  7.0027e+01,  1.0411e+01,  5.0637e+00,
            4.0639e+00,  1.3297e+01,  3.0445e+01,  1.4768e+00,  9.0399e-01,  8.4628e+00,  1.8631e+00,  2.0581e+00,
            8.1748e+01,  2.1348e+00,  6.9908e+00,  4.6871e+00,  4.0060e+00,  9.0634e+00,  6.4780e+00,  3.3827e+00,
            2.7371e+00,  1.3227e+01,  1.1238e+02,  3.6789e+01,  2.0156e+01,  1.4099e+02,  2.8025e+01,  1.3357e+01,
            5.5910e+00,  9.2154e+00,  1.0142e+02,  8.0994e+01,  1.0139e+02,  1.0297e+02,  8.7059e+01,  1.0224e+02]]]],
       dtype=torch.float64)
tensor([[nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        ...,
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan]])
tensor([[[[ 1.0000e+00,  2.0121e+16,  2.0871e+03, -1.2150e+02,  1.1584e+02,  9.4614e+01,  1.7655e+02,  1.4968e+02,
            5.9186e+01,  6.4225e+01,  1.4681e+02,  1.2555e+02,  1.4587e+02,  1.3124e+02,  1.0625e+02,  1.6970e+02,
           -8.9481e+01, -1.2804e-01,  9.7902e+01, -8.7950e+01, -4.4465e-02,  9.4614e+01, -6.9190e+01,  1.3636e+01,
            1.2268e+02, -1.7465e+02, -1.2150e+02, -9.8691e+01,  2.3403e+01,  1.1584e+02, -4.8239e+01,  4.2988e+00,
           -1.5434e+02, -9.0322e+01, -2.7524e+01,  5.5696e+01, -1.2056e+02, -3.2478e+01,  5.6493e+01,  8.9425e+00,
            9.4711e-01,  1.5983e+02, -8.9396e+01, -8.8004e+01, -1.0813e+02, -1.5779e+02, -8.9520e+01, -9.0743e+01,
           -1.4404e+02,  3.7885e+01,  8.5067e-01,  8.7955e-01,  1.7108e+00,  1.2885e+00,  3.4127e+00,  1.1691e+00,
            1.7282e+00,  2.7701e+00,  2.3123e+01,  2.0280e+01,  4.5535e+00,  1.8832e+01,  1.4191e+01,  1.2135e+01,
            1.4857e+00,  2.4388e+00,  1.4344e+01,  1.0912e+00,  1.7108e+00,  2.5853e+00,  1.3156e+00,  3.0321e+00,
            1.2381e+00,  8.5067e-01,  2.3047e+00,  1.2403e+00,  8.7955e-01,  1.6901e+00,  1.7304e+02,  2.8295e+00,
            3.8194e+00,  8.0889e+01,  1.4319e+02,  2.3998e+01,  6.4587e+01,  1.0627e+02,  1.4835e+02,  1.4839e+01,
            1.9887e+01,  4.6248e+00,  4.1587e+01,  9.4676e+01,  2.1845e+01,  4.2808e+01,  1.1131e+02,  6.9814e+01]]]],
       dtype=torch.float64)
tensor([[nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        ...,
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan]])
tensor([[[[ 3.0000e+00,  2.0121e+16,  2.2382e+03, -1.1457e+02,  1.0945e+02,  9.8255e+01,  1.7610e+02,  1.4711e+02,
            7.2049e+01,  6.3489e+01,  1.4008e+02,  9.7981e+01,  1.6307e+02,  1.2685e+02,  1.1018e+02,  1.0374e+02,
           -1.1611e+02, -5.8163e+00,  1.0192e+02, -1.3040e+02, -5.9148e+00,  9.8255e+01, -7.4477e+01,  1.1937e+01,
            1.2674e+02, -1.7553e+02, -1.1457e+02, -9.9373e+01,  2.5755e+01,  1.0945e+02, -3.6399e+01, -1.4544e+02,
           -1.5179e+02, -1.0904e+02, -4.7341e+01,  1.1076e+02, -1.6068e+02, -4.8402e+01,  8.7140e+01,  1.7231e+02,
           -7.3906e+00,  1.5414e+02, -9.3966e+01, -4.5671e+01,  4.2261e+01, -1.1964e+02,  1.8086e+01, -1.1372e+01,
           -3.0424e+01,  1.9088e+01,  1.6262e+00,  1.1555e+00,  5.5998e+00,  1.0427e+00,  1.9490e+00,  3.7436e+00,
            3.2090e+00,  4.3002e+00,  8.4366e+00,  1.7938e+00,  8.7047e+00,  2.4796e+01,  6.9884e+01,  1.2647e+01,
            2.6064e+00,  5.7478e+00,  1.4113e+01,  1.9710e+00,  5.5998e+00,  5.5197e+00,  4.9480e+00,  2.4867e+00,
            2.1224e+00,  1.6262e+00,  4.3539e+00,  2.6674e+00,  1.1555e+00,  4.2607e+00,  1.3345e+01,  2.0322e+01,
            5.7152e+00,  4.2881e+00,  2.0370e+00,  2.4950e+00,  1.8078e+00,  1.7292e+00,  4.2053e+01,  3.0696e+01,
            1.9527e+01,  1.5438e+01,  5.5741e+01,  1.0291e+02,  9.3203e+01,  1.0503e+02,  9.0168e+01,  1.1326e+02]]]],
       dtype=torch.float64)
tensor([[nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        ...,
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan]])

and so on. Please provide any help.