Python Lightning for sine wave simulation

Question

I am getting an error when i run the below code. The error says

MisconfigurationException: No training_step() method defined. Lightning Trainer expects as minimum a training_step(), train_dataloader() and configure_optimizers() to be defined.

Can someone please let me know what is the issue here? I am very new to Pytorch. I am trying to simulate Sin wave using MLP

import numpy as np ## using again numpy library for Sin function
import torch  ## using pytorch 
import matplotlib.pyplot as plt
import pytorch_lightning as pl
import torch.optim as optim
from torch import nn
from pytorch_lightning import Trainer
from sklearn.model_selection import train_test_split
import pandas as pd
from torch.utils.data import DataLoader

N=1000 ## 1000 samples to be generated
L=1000 ## length of each sample
T=20 ## width of wave
x = np.random.randn(1000)
y = np.sin(x)
df = pd.DataFrame({'x':x, 'y':y})
train, test = train_test_split(df, test_size=0.2, random_state=42, shuffle=True)
target_fields=['y']
train_features, train_targets = train.drop(target_fields, axis=1), train[target_fields]
test_features, test_targets = test.drop(target_fields, axis=1), test[target_fields]
class MLP(pl.LightningModule):
  def __init__(self):
    super(MLP,self).__init__()
    self.fc1 = nn.Linear(1, 10)
    self.fc2 = nn.Linear(10, 1)
def forward(self, x):
        x = torch.Relu(self.fc1(x))
        x = self.fc2(x)
        return x
l_rate = 0.2
mse_loss = nn.MSELoss(reduction = 'mean')

def train_dataloader(self):
        train_dataset = TensorDataset(torch.tensor(train_features.values).float(), torch.tensor(train_targets[['cnt']].values).float())
        train_loader = DataLoader(dataset = train_dataset, batch_size = 128)
        return train_loader
def test_dataloader(self):
        test_dataset = TensorDataset(torch.tensor(test_features.values).float(), torch.tensor(test_targets[['cnt']].values).float())
        test_loader = DataLoader(dataset = test_dataset, batch_size = 128)
        return test_loader
def configure_optimizers(self):
        return optim.SGD(self.parameters(), lr=l_rate)
def training_step(self, batch, batch_idx):
        x, y = batch
        logits = self.forward(x)
        loss = mse_loss(logits, y)
        # Add logging
        logs = {'loss': loss}
        return {'loss': loss, 'log': logs}
def test_step(self, batch, batch_idx):
        x, y = batch
        logits = self.forward(x)
        loss = mse_loss(logits, y)
        correct = torch.sum(logits == y.data)
        predictions_pred.append(logits)
        predictions_actual.append(y.data)
        return {'test_loss': loss, 'test_correct': correct, 'logits': logits}
def test_epoch_end(self, outputs):
        avg_loss = torch.stack([x['test_loss'] for x in outputs]).mean()
        logs = {'test_loss': avg_loss}      
        return {'avg_test_loss': avg_loss, 'log': logs, 'progress_bar': logs }

model = MLP()
trainer = Trainer(max_epochs = 50)  
trainer.fit(model)

Error

GPU available: False, used: False
TPU available: False, using: 0 TPU cores
IPU available: False, using: 0 IPUs
---------------------------------------------------------------------------
MisconfigurationException                 Traceback (most recent call last)
<ipython-input-9-7bdf5ac9771f> in <module>()
      1 model = MLP()
      2 trainer = Trainer(max_epochs = 50)
----> 3 trainer.fit(model)
3 frames
/usr/local/lib/python3.7/dist-packages/pytorch_lightning/trainer/configuration_validator.py in __verify_train_loop_configuration(self, model)
     50         if not has_training_step:
     51             raise MisconfigurationException(
---> 52                 "No `training_step()` method defined. Lightning `Trainer` expects as minimum a"
     53                 " `training_step()`, `train_dataloader()` and `configure_optimizers()` to be defined."
     54             )
MisconfigurationException: No `training_step()` method defined. Lightning `Trainer` expects as minimum a `training_step()`, `train_dataloader()` and `configure_optimizers()` to be defined.

Answer 1

You are missing 2 parameters in your trainer.fit() call. See the documentation