# Lab 3

## SCF Accounts

We have SCF (Statistical Computing Facility) accounts set up for this course. To set up the accounts, we need to ssh into the cluster. Say your account name is `s159-X`, then you need to run one of

```
ssh s159-X@gandalf.berkeley.edu
```

or

```
ssh s159-X@arwen.berkeley.edu
```

or

```
ssh s159-X@legolas.berkeley.edu
```

and complete the initial setup.

## First Homework
The first homework is a "warm up" for the first project. You'll be working in pairs to reproduce the figures in [this paper](http://arxiv.org/abs/1502.00505).
Working in pairs gives a feel for collaboration. How can we work together effectively?

1. Start by selecting a work partner for this homework. This person will also be your work partner for the first project (but not the others).

1. Select and write down the name of the team you will work as. The name of the team should be made from the first three letters of your Github usernames, in all lowercase. For example if your Github username is `Alice` and your partner's is `bobby`, your team name should be `ali-bob`.

1. When each of you visits the link from Piazza, after you accept your name from  the initial list, you will create your team with the appropriate team name (`ali-bob` in this case, make sure to use **your actual team name!**):

![ali-bob team creation](lab_fig/hw_team_signup.png)

Once you have accepted the assignment, you'll see a repository created for your team that you can both access. You should then clone that repository on your laptop and begin working, as indicated below.

You may find it useful to watch this brief video with an introduction to how assignments work:

<iframe width="560" height="315" src="https://www.youtube.com/embed/-52quDR2QSc" frameborder="0" allowfullscreen></iframe>

## Working Together

### Working on a separate branch

Each pair will share a single repository, and it can get messy fast. A good way to avoid mistakes and merge errors is to create a separate branch for your work

```
git checkout -b my-awesome-work
```

After adding changes that you're happy with, you should push the branch to the shared repo

```
git push origin my-awesome-work
```

### Creating the pull request

Once the branch is pushed, you can merge it into master with a pull request. Go to the repo on Github and click on the "New pull request" button

![New pull request](lab_fig/pr.png)

You'll see a drop down menu for "base" and "compare" or "head".
The "base" drop down menu chooses the branch you want to merge on to.

![Choosing master as the base branch](lab_fig/base_master.png)

The "compare" or "head" drop down menu chooses the branch you want to merge

![Choosing a head branch](lab_fig/compare_branch.png)

Now you can create the pull request and add general comments, comments on files, and comments on lines. If there isn't a merge error, Github will let you merge the branch.


## Working on the Homework

Use the rest of the lab time to work with your partner.