Output becomes zero after optimizer.step()

I encountered this error while i was trying train the model on my local gpu

Here : Machine-Learning-Collection/ML/Pytorch/object_detection/YOLO/

This is the test script that i have used to test the yolo-v1 model

import torch

import torch
import torch.nn as nn

from torch.utils.data import DataLoader
import torchvision.transforms.functional as F
import torchvision.transforms as transforms
import torch.optim as optim
from torch.autograd import Variable
from torch.nn.utils import clip_grad_norm_

from tqdm import tqdm
from utils import *
# from loss import *
from yololoss import *
from dataset import *
from model import *
import os

torch.autograd.set_detect_anomaly(True)

class Compose(object):

    def __init__(self,transforms):
        self.transforms = transforms

    def __call__(self,image,boxes):

        for t in self.transforms:
            image , boxes = t(image) , boxes

        return image , boxes


transform = Compose([
                    transforms.Resize((448, 448)),
                    transforms.ToTensor(),
                    # transforms.Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5)),
                    ])

if __name__ == '__main__':

    csv_file_path = 'PascalVOC_YOLO/100examples.csv'
    img_dir = 'PascalVOC_YOLO/images'
    label_path = 'PascalVOC_YOLO/labels'

    learning_rate = 1e-10
    num_workers = 2
    batch_size = 2
    weight_decay = 1e-4

    sample_dataset = VOCDataset( csv_file_path , img_dir , label_path, transform=transform)

    sample_loader = DataLoader(
        dataset=sample_dataset,
        batch_size=2,
        num_workers=2,
        pin_memory=True,
        shuffle=True,
        drop_last=True,
    )

    device = 'cuda'if torch.cuda.is_available() else 'cpu'

    model = Yolov1(split_size=7, num_boxes=2, num_classes=20).to(device).half()

    optimizer = optim.Adam( model.parameters() , lr=learning_rate , weight_decay=weight_decay)

    loss_func = YoloLoss().to(device)

    for _ in  range(2):

        print('iter : ',_,'\n')

        x , y = next( iter(sample_loader) )

        x , y = Variable(x).to(device).half() , Variable(y).to(device).half()

        # print( 'infinite : ' , torch.isfinite(x))

        # print('x : ',x)

        out = model(x)

        print('out : ',out , '\n')

        loss = loss_func(out,y)

        optimizer.zero_grad()
        loss.backward()
        optimizer.step()

        print( 'loss : ',loss , '\n')
        print( 'loss : data ', loss.data , '\n')
        print(' loss : grad ',loss.grad , '\n')

        for name, param in model.named_parameters():
            print(name, torch.isfinite(param.grad).all() , torch.max(abs(param.grad)) )

        print('\n')

Note : i am using half() because of the cuda error => RuntimeError: cuDNN error: CUDNN_STATUS_EXECUTION_FAILED

while running the script i was getting this output below

iter :  0

out :  tensor([[-0.1432,  0.0819,  0.0342,  ..., -0.0377, -0.0745,  0.1312],
        [ 0.1110, -0.0650,  0.2410,  ..., -0.0765,  0.3328,  0.1908]],
       device='cuda:0', dtype=torch.float16, grad_fn=<AddmmBackward>)

loss :  tensor(1., device='cuda:0', dtype=torch.float16, grad_fn=<ClampBackward>)

loss : data  tensor(1., device='cuda:0', dtype=torch.float16)

test.py:94: UserWarning: The .grad attribute of a Tensor that is not a leaf Tensor is being accessed. Its .grad attribute won't be populated during autograd.backward(). If you indeed want the gradient for a non-leaf Tensor, use .retain_grad() on the non-leaf Tensor. If you access the non-leaf Tensor by mistake, make sure you access the leaf Tensor instead. See github.com/pytorch/pytorch/pull/30531 for more informations.
  print(' loss : grad ',loss.grad , '\n')
 loss : grad  None

darknet.0.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.0.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.0.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.2.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.2.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.2.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.4.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.4.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.4.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.5.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.5.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.5.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.6.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.6.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.6.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.7.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.7.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.7.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.9.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.9.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.9.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.10.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.10.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.10.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.11.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.11.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.11.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.12.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.12.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.12.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.13.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.13.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.13.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.14.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.14.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.14.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.15.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.15.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.15.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.16.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.16.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.16.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.17.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.17.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.17.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.18.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.18.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.18.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.20.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.20.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.20.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.21.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.21.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.21.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.22.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.22.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.22.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.23.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.23.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.23.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.24.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.24.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.24.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.25.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.25.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.25.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.26.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.26.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.26.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.27.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.27.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.27.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
fcs.1.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
fcs.1.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
fcs.4.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
fcs.4.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)


iter :  1

out :  tensor([[nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan]], device='cuda:0',
       dtype=torch.float16, grad_fn=<AddmmBackward>)

[W python_anomaly_mode.cpp:104] Warning: Error detected in MseLossBackward. Traceback of forward call that caused the error:
  File "test.py", line 86, in <module>
    loss = loss_func(out,y)
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/nn/modules/module.py", line 889, in _call_impl
    result = self.forward(*input, **kwargs)
  File "/mnt/e/workspace/@training/@datasets/cnns/yolo/yolo-v1-pytorch/loss.py", line 120, in forward
    torch.flatten(exists_box * target[..., :20], end_dim=-2,),
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/nn/modules/module.py", line 889, in _call_impl
    result = self.forward(*input, **kwargs)
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/nn/modules/loss.py", line 528, in forward
    return F.mse_loss(input, target, reduction=self.reduction)
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/nn/functional.py", line 2929, in mse_loss
    return torch._C._nn.mse_loss(expanded_input, expanded_target, _Reduction.get_enum(reduction))
 (function _print_stack)
Traceback (most recent call last):
  File "test.py", line 89, in <module>
    loss.backward()
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/tensor.py", line 245, in backward
    torch.autograd.backward(self, gradient, retain_graph, create_graph, inputs=inputs)
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/autograd/__init__.py", line 147, in backward
    allow_unreachable=True, accumulate_grad=True)  # allow_unreachable flag
RuntimeError: Function 'MseLossBackward' returned nan values in its 0th output.
(dev) buckaroo@hansolo:/mnt/e/workspace/@training/@datasets/cnns/yolo/yolo-v1-pytorch$ python3 test.py
iter :  0

out :  tensor([[-0.1044, -0.3135, -0.4897,  ..., -0.1079, -0.0055, -0.0380],
        [ 0.1190, -0.3154, -0.0910,  ..., -0.0995, -0.1595, -0.0576]],
       device='cuda:0', dtype=torch.float16, grad_fn=<AddmmBackward>)

loss :  tensor(1.0010, device='cuda:0', dtype=torch.float16, grad_fn=<AddBackward0>)

loss : data  tensor(1.0010, device='cuda:0', dtype=torch.float16)

test.py:94: UserWarning: The .grad attribute of a Tensor that is not a leaf Tensor is being accessed. Its .grad attribute won't be populated during autograd.backward(). If you indeed want the gradient for a non-leaf Tensor, use .retain_grad() on the non-leaf Tensor. If you access the non-leaf Tensor by mistake, make sure you access the leaf Tensor instead. See github.com/pytorch/pytorch/pull/30531 for more informations.
  print(' loss : grad ',loss.grad , '\n')
 loss : grad  None

darknet.0.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.0.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.0.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.2.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.2.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.2.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.4.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.4.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.4.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.5.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.5.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.5.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.6.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.6.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.6.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.7.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.7.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.7.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.9.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.9.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.9.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.10.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.10.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.10.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.11.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.11.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.11.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.12.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.12.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.12.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.13.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.13.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.13.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.14.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.14.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.14.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.15.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.15.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.15.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.16.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.16.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.16.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.17.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.17.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.17.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.18.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.18.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.18.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.20.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.20.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.20.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.21.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.21.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.21.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.22.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.22.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.22.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.23.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.23.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.23.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.24.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.24.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.24.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.25.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.25.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.25.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.26.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.26.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.26.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.27.conv.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.27.batchnorm.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
darknet.27.batchnorm.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
fcs.1.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
fcs.1.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
fcs.4.weight tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)
fcs.4.bias tensor(True, device='cuda:0') tensor(0., device='cuda:0', dtype=torch.float16)

iter :  1

out :  tensor([[nan, nan, nan,  ..., nan, nan, nan],
        [nan, nan, nan,  ..., nan, nan, nan]], device='cuda:0',
       dtype=torch.float16, grad_fn=<AddmmBackward>)

Observations

  • As you can see that for the first time , the model out is a valid tensor with values ( i.e before optimizer.step() )
  • when the iteration 1 begins ( i.e after optimizer.step() ) output becomes nan

Debug method : 0

  • after setting this torch.autograd.set_detect_anomaly(True) globally
  • i found this result below
[W python_anomaly_mode.cpp:104] Warning: Error detected in MseLossBackward. Traceback of forward call that caused the error:
  File "test.py", line 86, in <module>
    loss = loss_func(out,y)
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/nn/modules/module.py", line 889, in _call_impl
    result = self.forward(*input, **kwargs)
  File "/mnt/e/workspace/@training/@datasets/cnns/yolo/yolo-v1-pytorch/loss.py", line 120, in forward
    torch.flatten(exists_box * target[..., :20], end_dim=-2,),
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/nn/modules/module.py", line 889, in _call_impl
    result = self.forward(*input, **kwargs)
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/nn/modules/loss.py", line 528, in forward
    return F.mse_loss(input, target, reduction=self.reduction)
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/nn/functional.py", line 2929, in mse_loss
    return torch._C._nn.mse_loss(expanded_input, expanded_target, _Reduction.get_enum(reduction))
 (function _print_stack)
Traceback (most recent call last):
  File "test.py", line 89, in <module>
    loss.backward()
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/tensor.py", line 245, in backward
    torch.autograd.backward(self, gradient, retain_graph, create_graph, inputs=inputs)
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/autograd/__init__.py", line 147, in backward
    allow_unreachable=True, accumulate_grad=True)  # allow_unreachable flag
RuntimeError: Function 'MseLossBackward' returned nan values in its 0th output.

so i have tried

  • clamping the loss tensors torch.clamp(value, min=0.0 , max=1.0) in loss.py
  • adding epsilon (1e-6) after torch.sqrt() like torch.sqrt(val+epsilon) in loss.py

But this didnot fix my issue.

Reference

Getting NaN values in backward pass

Output of Model is nan every time

Nan Loss coming after some time

Getting Nan after first iteration with custom loss

Weights become NaN values after first batch step

Why nan after backward pass?

NaN values popping up during loss.backward()

Debugging neural networks

So kindly help me debug this issue , thanks in advance

Calling model.half() can easily create under/overflows, which could explain the NaN values in the forward/backward pass, which is why we recommend using torch.cuda.amp for mixed-precision training.
Are you seeing the first cudnn error using amp?
If so, could you post a minimal, executable code snippet as well as the output of python -m torch.utils.collect_env, please?

1 Like

Thanks for you advice , i will try and let you know :slight_smile:

i have used torch.cuda.amp for mixed-precision training , as below

    device = 'cuda'if torch.cuda.is_available() else 'cpu'

    model = Yolov1(split_size=7, num_boxes=2, num_classes=20).to(device).half()

    optimizer = optim.Adam( model.parameters() , lr=learning_rate , weight_decay=weight_decay)

    loss_func = YoloLoss().half()

    scaler = torch.cuda.amp.GradScaler()

    for _ in  range(2):

        print('iter : ',_,'\n')

        x , y = next( iter(sample_loader) )

        with torch.cuda.amp.autocast():

            x , y = Variable(x).to(device).half() , Variable(y).to(device).half()

            # print( 'infinite : ' , torch.isfinite(x))

            # print('x : ',x)

            optimizer.zero_grad()

            out = model(x)

        print('out : ',out , '\n')

        loss = loss_func(out,y)

        scaler.scale(loss).backward()
        scaler.step(optimizer)
        scaler.update()

        print( 'loss : ',loss , '\n')
        print( 'loss : data ', loss.data , '\n')
        print(' loss : grad ',loss.grad , '\n')

        for name, param in model.named_parameters():
            print(name, torch.isfinite(param.grad).all() , torch.max(abs(param.grad)) )
            print(name,"->data",torch.isfinite(param.grad.data).all(),"\n")

        print('\n')

And Even still i am getting as below,

iter :  0

out :  tensor([[ 0.0726,  0.1926, -0.2280,  ..., -0.2744,  0.1210, -0.1783],
        [ 0.1121,  0.0148, -0.0810,  ..., -0.2537,  0.2219, -0.3547]],
       device='cuda:0', dtype=torch.float16, grad_fn=<AddmmBackward>)

[W python_anomaly_mode.cpp:104] Warning: Error detected in MseLossBackward. Traceback of forward call that caused the error:
  File "test.py", line 95, in <module>
    loss = loss_func(out,y)
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/nn/modules/module.py", line 889, in _call_impl
    result = self.forward(*input, **kwargs)
  File "/mnt/e/workspace/@training/@datasets/cnns/yolo/yolo-v1-pytorch/loss.py", line 109, in forward
    torch.flatten(exists_box * target[..., :20], end_dim=-2,),
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/nn/modules/module.py", line 889, in _call_impl
    result = self.forward(*input, **kwargs)
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/nn/modules/loss.py", line 528, in forward
    return F.mse_loss(input, target, reduction=self.reduction)
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/nn/functional.py", line 2929, in mse_loss
    return torch._C._nn.mse_loss(expanded_input, expanded_target, _Reduction.get_enum(reduction))
 (function _print_stack)
Traceback (most recent call last):
  File "test.py", line 97, in <module>
    scaler.scale(loss).backward()
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/tensor.py", line 245, in backward
    torch.autograd.backward(self, gradient, retain_graph, create_graph, inputs=inputs)
  File "/home/buckaroo/miniconda3/envs/dev/lib/python3.7/site-packages/torch/autograd/__init__.py", line 147, in backward
    allow_unreachable=True, accumulate_grad=True)  # allow_unreachable flag
RuntimeError: Function 'MseLossBackward' returned nan values in its 0th output.

can you kindly help me out !

The GradScaler in amp uses an initially high scaling value, which could create invalid gradients in the first iteration(s), which is expected. If the scaler sees these invalid gradients, the optimizer.step() will be skipped and the scaling value will be reduced.
If you add anomaly detection at the beginning of the training, this would raise this “false positive” issue, so you should either set the initial scale factor to a lower value or enable anomaly detection after the gradient scaler stabilized.

Thank you for the help, i removed half() and it seems to be working

    sample_dataset = VOCDataset( csv_file_path , img_dir , label_path, transform=transform)

    sample_loader = DataLoader(
        dataset=sample_dataset,
        batch_size=2,
        num_workers=2,
        pin_memory=True,
        shuffle=True,
        drop_last=True,
    )

    device = 'cuda'if torch.cuda.is_available() else 'cpu'

    model = Yolov1(split_size=7, num_boxes=2, num_classes=20).to(device)

    optimizer = optim.Adam( model.parameters() , lr=learning_rate , weight_decay=weight_decay)

    loss_func = YoloLoss()

    scaler = torch.cuda.amp.GradScaler()

    for _ in  range(2):

        print('iter : ',_,'\n')

        x , y = next( iter(sample_loader) )

        with torch.cuda.amp.autocast():

            x , y = Variable(x).to(device) , Variable(y).to(device)

            optimizer.zero_grad()

            out = model(x)

        print('out : ',out , '\n')

        loss = loss_func(out,y)

        scaler.scale(loss).backward()
        scaler.step(optimizer)
        scaler.update()

        print( 'loss : ',loss , '\n')
        print( 'loss : data ', loss.data , '\n')
        print(' loss : grad ',loss.grad , '\n')