Loading a huge dataset batch-wise to train pytorch

I am training a LSTM in-order to classify the time-series data into 2 classes(0 and 1).I have huge data-set on the drive where where the 0-class and the 1-class data are located in different folders.I am trying to train the LSTM batch-wise using by creating a Dataset class and wrapping the DataLoader around it. I have to do pre-processing such as reshaping.Here’s my code which does that

class LoadingDataset(Dataset):
  def __init__(self,data_root1,data_root2,file_name):
    self.data_root1=data_root1#Has the path for class1 data
    self.data_root2=data_root2#Has the path for class0 data
    self.fileap1= pd.DataFrame()#Stores class 1 data
    self.fileap0 = pd.DataFrame()#Stores class 0 data
    self.file_name=file_name#List of all the files at data_root1 and data_root2
    self.labs1=None #Will store the class 1 labels
    self.labs0=None #Will store the class 0 labels

  def __len__(self):
    return len(self.fileap1) 

  def __getitem__(self, index):        
    self.fileap1 = pd.read_csv(self.data_root1+self.file_name[index],header=None)#read the csv file for class 1
    self.fileap1=self.fileap1.iloc[1:,1:].values.reshape(-1,WINDOW+1,1)#reshape the file for lstm
    self.fileap0 = pd.read_csv(self.data_root2+self.file_name[index],header=None)#read the csv file for class 0
    self.fileap0=self.fileap0.iloc[1:,1:].values.reshape(-1,WINDOW+1,1)#reshape the file for lstm
    self.labs1=np.array([1]*len(self.fileap1)).reshape(-1,1)#create the labels 1 for the csv file
    self.labs0=np.array([0]*len(self.fileap0)).reshape(-1,1)#create the labels 0 for the csv file
    # print(self.fileap1.shape,' ',self.fileap0.shape)
    # print(self.labs1.shape,' ',self.labs0.shape)
    self.fileap1=np.append(self.fileap1,self.fileap0,axis=0)#combine the class 0 and class one data
    self.fileap1 = torch.from_numpy(self.fileap1).float()
    self.labs1=np.append(self.labs1,self.labs0,axis=0)#combine the label0 and label 1 data
    self.labs1 = torch.from_numpy(self.labs1).int()
    # print(self.fileap1.shape,' ',self.fileap0.shape)
    # print(self.labs1.shape,' ',self.labs0.shape)

    return self.fileap1,self.labs1

data_root1 = '/content/gdrive/My Drive/Data/Processed_Data/Folder1/One_'#location of class 1 data
data_root2 = '/content/gdrive/My Drive/Data/Processed_Data/Folder0/Zero_'#location of class 0 data
training_set=LoadingDataset(data_root1,data_root2,train_ind)#train_ind is a list of file names that have to be read from data_root1 and data_root2
training_generator = DataLoader(training_set,batch_size =2,num_workers=4)

for epoch in range(num_epochs):
  model.train()#Setting the model to train mode after eval mode to train for next epoch once the testing for that epoch is finished
  for i, (inputs, targets) in enumerate(train_loader):

I get this error when the run this code

RuntimeError: Traceback (most recent call last): File “/usr/local/lib/python3.6/dist-packages/torch/utils/data/_utils/worker.py”, line 99, in _worker_loop samples = collate_fn([dataset[i] for i in batch_indices]) File “/usr/local/lib/python3.6/dist-packages/torch/utils/data/_utils/collate.py”, line 68, in default_collate return [default_collate(samples) for samples in transposed] File “/usr/local/lib/python3.6/dist-packages/torch/utils/data/_utils/collate.py”, line 68, in return [default_collate(samples) for samples in transposed] File “/usr/local/lib/python3.6/dist-packages/torch/utils/data/_utils/collate.py”, line 43, in default_collate return torch.stack(batch, 0, out=out) RuntimeError: invalid argument 0: Sizes of tensors must match except in dimension 0. Got 96596 and 25060 in dimension 1 at /pytorch/aten/src/TH/generic/THTensor.cpp:711

My Questions are 1.Have I Implemented this correctly, is this how you pre-process and then train a dataset batch-wise?

2.The batch_size of DataLoader and batch_size of the LSTM are different since the batch_size of DataLoader refers to the no. of files, whereas batch_size of the LSTM model refers to the no. of instances, so will I get another error here?

3.I have no idea how to scale this data-set since the MinMaxScaler has to be applied to the dataset in its entirety.

Responses are appreciated.Please let me know if I have to create separate posts for each question.

Thank You.