Conflict

Background

Let's make conflict

Let's make an intential conflict

Create a branch for implementing training loop in train.py

git status
git checkout main  # ensure if you are in `main` branch
git checkout -b dev/train

This is our update on train.py.

train.py

import torch
from torch import nn

from data_loader import get_dataloaders
from model import MLP


def train(config):
    train_loader, val_loader = get_dataloaders(
        config["csv_path"],
        config["batch_size"],
        config["train_fraction"],
        config["shuffle_train"],
        config["num_workers"],
    )

    # Get feature dim (e.g. 4) and target dim (e.g. 1) to build the model.
    example_features, example_targets = train_loader.dataset[0]
    model = MLP(
        example_features.shape[0],
        example_targets.shape[0],
        config["hidden_sizes"],
        config["activation"],
    )
    device = torch.device(config["device"])
    model = model.to(device)

    loss_fn = nn.MSELoss()
    optimizer = torch.optim.Adam(model.parameters(), lr=config["lr"])

    # Training looop
    for _ in range(config["epochs"]):
        model.train()
        for batch_features, batch_targets in train_loader:
            batch_features = batch_features.to(device)
            batch_targets = batch_targets.to(device)
            predictions = model(batch_features)  # Forward pass
            loss = loss_fn(predictions, batch_targets)  # Compute loss
            optimizer.zero_grad()  # Clear old gradients
            loss.backward()  # Backprop: compute d(loss)/d(weights).
            optimizer.step()  # Apply the update for this batch.

    return model

Note

VS Code shows the changes (before staging)

Change views in VS Code

Diff views in VS Code

Stage and commit.

git add train.py
git commit -m "add training loop"

At the same time, you also make changes in .gitignore

.gitignore

*.csv
data
dataset.csv
__pycache__
*.pdf

Stage and commit.

git add .gitignore
git commit -m "update gitignore"

Now, go back to main branch, and make the changes at the same lines where you made changes in dev/train branch.

git checkout main

.gitignore

*.csv
dataset.csv
__pycache__
data
*.png

Commit this change

git add .
git commit -m "add png to gitignore"

Now, you have conflicting changes in .gitignore between the two branches:

dev/train branchmain branch

.gitignore

*.csv
data
dataset.csv
__pycache__
*.pdf

.gitignore

*.csv
dataset.csv
__pycache__
data
*.png

Both branches modified the same lines of .gitignore differently: the order of data and dataset.csv is swapped, and each branch added a different new entry (*.pdf vs *.png). Git cannot decide which version to keep, so it will raise a conflict.

Merge the conflicting changes

Try merge dev/train to main

git status  # check if you are at `main` branch. If not, `git checkout main`
git merge dev/train

You will see an error message in your terminal:

$ git merge dev/train
Auto-merging .gitignore
CONFLICT (content): Merge conflict in .gitignore
Automatic merge failed; fix conflicts and then commit the result.

VS Code shows the conflict status

Resolve the conflict by editing .gitignore to the desired final content:

VS CodeText editor

Open .gitignore. VS Code highlights the conflict and shows inline buttons. Click Accept Current Change, Accept Incoming Change, or Accept Both Changes to pick which version to keep, then save.

Open .gitignore. You will see conflict markers:

<<<<<<< HEAD
dataset.csv
__pycache__
data
*.png
=======
data
dataset.csv
__pycache__
*.pdf
>>>>>>> dev/train

Manually edit the file to the intended content, removing all conflict markders: <<<<<<<, =======, and >>>>>>>.

After resolving, stage and commit:

git add .gitignore
git commit -m "resolve merge conflict in .gitignore"