Submitting a PR

Submitting a PR#

Thrust uses Github to manage all open-source development, including bug tracking, pull requests, and design discussions. This document details how to get started as a Thrust contributor.

An overview of this process is:

  1. Clone the Thrust repository

  2. Setup a fork of Thrust

  3. Setup your environment

  4. Create a development branch

  5. Local development loop

  6. Push development branch to your fork

  7. Create pull request

  8. Address feedback and update pull request

  9. When your PR is approved…

Clone the Thrust Repository#

To get started, clone the main repository to your local computer. Thrust should be cloned recursively to setup the CUB submodule (required for CUDA acceleration).

git clone --recursive https://github.com/NVIDIA/thrust.git
cd thrust

Setup a Fork of Thrust#

You’ll need a fork of Thrust on Github to create a pull request. To setup your fork:

  1. Create a Github account (if needed)

  2. Go to the Thrust Github page

  3. Click “Fork” and follow any prompts that appear.

Once your fork is created, setup a new remote repo in your local Thrust clone:

git remote add github-fork git@github.com:<GITHUB_USERNAME>/thrust.git

If you need to modify CUB, too, go to the CUB Github page and repeat this process. Create CUB’s github-fork remote in the thrust/dependencies/cub submodule.

Setup Your Environment#

Git Environment#

If you haven’t already, this is a good time to tell git who you are. This information is used to fill out authorship information on your git commits.

git config --global user.name "John Doe"
git config --global user.email johndoe@example.com

Configure CMake builds#

Thrust uses CMake for its primary build system. To configure, build, and test your checkout of Thrust:

# Create build directory:
mkdir build
cd build

# Configure -- use one of the following:
cmake ..                                 # Command line interface
cmake -DTHRUST_INCLUDE_CUB_CMAKE=ON ..   # Enables CUB development targets
ccmake ..                # ncurses GUI (Linux only)
cmake-gui                # Graphical UI, set source/build directories in the app

# Build:
cmake --build . -j <num jobs>   # invokes make (or ninja, etc)

# Run tests and examples:
ctest

See CMake Options for details on customizing the build. To enable CUB tests and examples, set the THRUST_INCLUDE_CUB_CMAKE option to ON. Additional CMake options for CUB are listed here.

Create a Development Branch#

All work should be done in a development branch (also called a “topic branch”) and not directly in the main branch. This makes it easier to manage multiple in-progress patches at once, and provides a descriptive label for your patch as it passes through the review system.

To create a new branch based on the current main:

# Checkout local main branch:
cd /path/to/thrust/sources
git checkout main

# Sync local main branch with github:
git pull

# Create a new branch named `my_descriptive_branch_name` based on main:
git checkout -b my_descriptive_branch_name

# Verify that the branch has been created and is currently checked out:
git branch

Thrust branch names should follow a particular pattern:

  • For new features, name the branch feature/<name>

  • For bugfixes associated with a github issue, use bug/github/<bug-description>-<bug-id>

    • Internal nvidia and gitlab bugs should use nvidia or gitlab in place of github.

If you plan to work on CUB as part of your patch, repeat this process in the thrust/dependencies/cub submodule.

Local Development Loop#

Edit, Build, Test, Repeat#

Once the topic branch is created, you’re all set to start working on Thrust code. Make some changes, then build and test them:

# Implement changes:
cd /path/to/thrust/sources
emacs thrust/some_file.h # or whatever editor you prefer

# Create / update a unit test for your changes:
emacs testing/some_test.cu

# Check that everything builds and tests pass:
cd /path/to/thrust/build/directory
cmake --build . -j <num jobs>
ctest

Creating a Commit#

Once you’re satisfied with your patch, commit your changes:

Thrust-only Changes#

# Manually add changed files and create a commit:
cd /path/to/thrust
git add thrust/some_file.h
git add testing/some_test.cu
git commit

# Or, if possible, use git-gui to review your changes while building your patch:
git gui

Thrust and CUB Changes#

# Create CUB patch first:
cd /path/to/thrust/dependencies/cub
# Manually add changed files and create a commit:
git add cub/some_file.cuh
git commit

# Create Thrust patch, including submodule update:
cd /path/to/thrust/
git add dependencies/cub # Updates submodule info
git add thrust/some_file.h
git add testing/some_test.cu
git commit

# Or, if possible, use git-gui to review your changes while building your patch:
cd /path/to/thrust/dependencies/cub
git gui
cd /path/to/thrust
git gui # Include dependencies/cub as part of your commit

Writing a Commit Message#

Your commit message will communicate the purpose and rationale behind your patch to other developers, and will be used to populate the initial description of your Github pull request.

When writing a commit message, the following standard format should be used, since tools in the git ecosystem are designed to parse this correctly:

First line of commit message is a short summary (<80 char)
<Second line left blank>
Detailed description of change begins on third line. This portion can
span multiple lines, try to manually wrap them at something reasonable.

Blank lines can be used to separate multiple paragraphs in the description.

If your patch is associated with another pull request or issue in the main
Thrust repository, you should reference it with a `#` symbol, e.g.
#1023 for issue 1023.

For issues / pull requests in a different github repo, reference them using
the full syntax, e.g. NVIDIA/cub#4 for issue 4 in the NVIDIA/cub repo.

Markdown is recommended for formatting more detailed messages, as these will
be nicely rendered on Github, etc.

Push Development Branch to your Fork#

Once you’ve committed your changes to a local development branch, it’s time to push them to your fork:

cd /path/to/thrust/checkout
git checkout my_descriptive_branch_name # if not already checked out
git push --set-upstream github-fork my_descriptive_branch_name

--set-upstream github-fork tells git that future pushes/pulls on this branch should target your github-fork remote by default.

If have CUB changes to commit as part of your patch, repeat this process in the thrust/dependencies/cub submodule.

Create Pull Request#

To create a pull request for your freshly pushed branch, open your github fork in a browser by going to https://www.github.com/<GITHUB_USERNAME>/thrust. A prompt may automatically appear asking you to create a pull request if you’ve recently pushed a branch.

If there’s no prompt, go to “Code” > “Branches” and click the appropriate “New pull request” button for your branch.

If you would like a specific developer to review your patch, feel free to request them as a reviewer at this time.

The Thrust team will review your patch, test it on NVIDIA’s internal CI, and provide feedback.

If have CUB changes to commit as part of your patch, repeat this process with your CUB branch and fork.

Address Feedback and Update Pull Request#

If the reviewers request changes to your patch, use the following process to update the pull request:

# Make changes:
cd /path/to/thrust/sources
git checkout my_descriptive_branch_name
emacs thrust/some_file.h
emacs testing/some_test.cu

# Build + test
cd /path/to/thrust/build/directory
cmake --build . -j <num jobs>
ctest

# Amend commit:
cd /path/to/thrust/sources
git add thrust/some_file.h
git add testing/some_test.cu
git commit --amend
# Or
git gui # Check the "Amend Last Commit" box

# Update the branch on your fork:
git push -f

At this point, the pull request should show your recent changes.

If have CUB changes to commit as part of your patch, repeat this process in the thrust/dependencies/cub submodule, and be sure to include any CUB submodule updates as part of your commit.

When Your PR is Approved#

Once your pull request is approved by the Thrust team, no further action is needed from you. We will handle integrating it since we must coordinate changes to main with NVIDIA’s internal perforce repository.

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