We appreciate all kinds of help, so thank you!
You can contribute in many ways to this project.
This is a good point to start, when you find a problem please add
it to the issue tracker <https://github.com/Qiskit/qiskit-aer/issues>_.
The ideal report should include the steps to reproduce it.
To help less advanced users is another wonderful way to start. You can
help us close some opened issues. This kind of tickets should be
labeled as question.
If you have an idea for a new feature please open a ticket labeled as
enhancement. If you could also add a piece of code with the idea
or a partial implementation it would be awesome.
We'd love to accept your code! Before we can, we have to get a few legal requirements sorted out. By signing a contributor license agreement (CLA), we ensure that the community is free to use your contributions.
When you contribute to the Qiskit project with a new pull request, a bot will
evaluate whether you have signed the CLA. If required, the bot will comment on
the pull request, including a link to accept the agreement. The
individual CLA <https://qiskit.org/license/qiskit-cla.pdf>_ document is
available for review as a PDF.
NOTE: If you work for a company that wants to allow you to contribute your work,
then you'll need to sign a corporate CLA <https://qiskit.org/license/qiskit-corporate-cla.pdf>_
and email it to us at qiskit@us.ibm.com.
Most of the required dependencies can be installed via pip, using the
requirements-dev.txt file, eg:
pip install -U -r requirements-dev.txt
As we are dealing with languages that build to native binaries, we will
need to have installed any of the supported CMake build tools <https://cmake.org/cmake/help/v3.5/manual/cmake-generators.7.html>_.
We do support most of the common available toolchains like: gcc, clang, Visual Studio. The only required requisite is that the toolchain needs to support C++14.
Mac
On Mac we have various options depending on the compiler we want to use. If we want to use Apple's Clang compiler, we need to install an extra library for supporting OpenMP: libomp. The CMake build system will warn you otherwise. To install it manually: you can type:
$ brew install libomp
We do recommend installing OpenBLAS, which is our default choice:
$ brew install openblas
CMake build system will search for other BLAS implementation alternatives if OpenBLAS is not installed in the system.
You further need to have Command Line Tools installed on MacOS:
$ xcode-select --install
Linux (Ubuntu >= 16.04)
Most of the major distributions come with a BLAS and LAPACK library implementation, and this is enough to build all the simulators, but we do recommend using OpenBLAS here as well, so in order to install it you have to type:
$ sudo apt install libopenblas-dev
Windows
On Windows you must have Anaconda3 installed in the system, and We recommend installing Visual Studio 2017 (Communit Edition). The same rules applies when searching for an OpenBLAS implementation, if CMake can't find one suitable implementation installed in the system, it will take the BLAS library from the Anaconda3 environment.
There are two ways of building Aer simulators, depending on our goal they are:
- Build Terra compatible addon.
- Build standalone executable
Terra addon
For the former, we just need to call the setup.py script:
qiskit-aer$ python ./setup.py bdist_wheel
We are using scikit-build <https://scikit-build.readthedocs.io/en/latest/>_ as a substitute of setuptools.
This is basically the glue between setuptools and CMake, so there are various options to pass variables to CMake, and
the undelying build system (depending on your platform). The way to pass variables is:
qiskit-aer$ python ./setup.py bdist_wheel -- -DCMAKE_VARIABLE=Values -- -Makefile_or_VisuaStudio_Flag
So a real example could be:
qiskit-aer$ python ./setup.py bdist_wheel -- -j8
This is setting the CMake variable STATIC_LINKING to value True so CMake will try to create an statically linked cython
library, and is passing -j8 flag to the underlaying build system, which in this case is Makefile, telling it that we want to
build in parallel, using 8 processes.
N.B. on MacOS:, you may need to turn off static linking and specify your platform name, e.g.:
qiskit-aer$ python ./setup.py bdist_wheel --plat-name macosx-10.9-x86_64 -- -DSTATIC_LINKING=False -- -j8
After this command is executed successfully, we will have a wheel package into the dist/ directory, so next step is installing it:
qiskit-aer/$ cd dist
qiskit-aer/dist$ pip install qiskit_aer-<...>.whl
Standalone executable
If we want to build an standalone executable, we have to use CMake directly. The preferred way CMake is meant to be used, is by setting up an "out of source" build. So in order to build our standalone executable, we have to follow these steps:
All platforms
qiskit-aer$ mkdir out
qiskit-aer$ cd out
qiskit-aer/out$ cmake ..
qiskit-aer/out$ cmake --build . --config Release -- -j4
Once built, you will have your standalone executable into the Release or Debug
directory (depending on the type of building choosen with the --config option):
qiskit-aer/out$ cd Release
qiskit-aer/out/Release$ ls
aer_simulator_cpp
There are some useful flags that can be set during cmake command invocation and
will help you change some default behavior. To make use of them, you just need to
pass them right after -D cmake argument. Example:
qiskit-aer/out$ cmake -DUSEFUL_FLAG=Value ..
In the case of building the Terra addon, you have to pass these flags after writing
-- at the end of the python command line, eg:
qiskit-aer$ python ./setup.py bdist_wheel -- -DUSEFUL_FLAG=Value
These are the flags:
USER_LIB_PATH This flag tells CMake to look for libraries that are needed by some of the native components to be built, but they are not in a common place where CMake could find it automatically.
Values: An absolute path with file included.
Default: No value.
Example: ``cmake -DUSER_LIB_PATH=C:\path\to\openblas\libopenblas.so ..``
STATIC_LINKING Tells the build system whether to create static versions of the programs being built or not. NOTE: On MacOS static linking is not fully working for all versions of GNU G++/Clang compilers, so depending on the version of the compiler installed in the system, enable this flag in this platform could cause errors.
Values: True|False
Default: False
Example: ``cmake -DSTATIC_LINKING=True ..``
BUILD_TESTS It will tell the build system to build C++ tests along with the simulator.
Values: True|False
Default: False
Example: ``cmake -DBUILD_TESTS=True ..``
CMAKE_CXX_COMPILER This is an internal CMake flag. It forces CMake to use the provided toolchain to build everthing. If it's not set, CMake system will use one of the toolchains installed in system.
Values: g++|clang++|g++-8
Default: Depends on the running platform and the toolchains installed
Example: ``cmake -DCMAKE_CXX_COMPILER=g++``
Almost every code contribution should be accompained by it's corresponding set of tests. You won't probably hear complaints if there are too many tests in your PR :), but the other way around is unnacceptable :( We have two types of tests in the codebase: Qiskit Terra integration tests and Standalone integration tests.
For Qiskit Terra integration tests, you first need to build and install the Terra addon,
and then run unittest Python framework.
qiskit-aer$ python ./setup.py install
# if you had to use --plat-name macosx-10.9-x86_64 for bdist_wheel then you need to do this for install:
# python ./setup.py install -- -DCMAKE_OSX_DEPLOYMENT_TARGET:STRING=10.9 -DCMAKE_OSX_ARCHITECTURES:STRING=x86_64
qiskit-aer$ python -m unittest discover -s test -v
The integration tests for Terra addon are included in: test/terra.
For the Standalone version of the simulator, we have C++ tests that use the Catch library.
Tests are located in test/src directory, and in order to run them, you have to build them first:
qiskit-aer$ mkdir out
qiskit-aer$ cd out
qiskit-aer/out$ cmake .. -DBUILD_TESTS=True
qiskit-aer/out$ cmake --build . --config Release -- -j4
qiskit-aer/out$ ctest -VV
Please submit clean code and please make effort to follow existing conventions in order to keep it as readable as possible.
TODO: Decide code convention
A linter (clang-tidy) is passed automatically every time a building is invoqued. It will stop the current build if detects style erros, or common pitfalls.
You are welcome to contribute wherever in the code you want to, of course, but we recommend taking a look at the "Good first contribution" label into the issues and pick one. We would love to mentor you!
Review the parts of the documentation regarding the new changes and update it if it's needed.
We use GitHub pull requests <https://help.github.com/articles/about-pull-requests>_
to accept the contributions.
A friendly reminder! We'd love to have a previous discussion about the best way to implement the feature/bug you are contributing with. This is a good way to improve code quality in our beloved simulators!, so remember to file a new Issue before starting to code for a solution.
So after having discussed the best way to land your changes into the codebase, you are ready to start coding (yay!). We have two options here:
- You think your implementation doesn't introduce a lot of code, right?. Ok, no problem, you are all set to create the PR once you have finished coding. We are waiting for it!
- Your implementation does introduce many things in the codebase. That sounds great! Thanks!. In this case you can start coding and create a PR with the word: [WIP] as a prefix of the description. This means "Work In Progress", and allow reviewers to make micro reviews from time to time without waiting to the big and final solution... otherwise, it would make reviewing and coming changes pretty difficult to accomplish. The reviewer will remove the [WIP] prefix from the description once the PR is ready to merge.
When submitting a pull request and you feel it is ready for review, please double check that:
- the code follows the code style of the project. For convenience, you can
execute
make styleandmake lintlocally, which will print potential style warnings and fixes. - the documentation has been updated accordingly. In particular, if a function or class has been modified during the PR, please update the docstring accordingly.
- your contribution passes the existing tests, and if developing a new feature, that you have added new tests that cover those changes.
- you add a new line to the
CHANGELOG.rstfile, in theUNRELEASEDsection, with the title of your pull request and its identifier (for example, "Replace OldComponent with FluxCapacitor (#123)".
Please follow the next rules for the commit messages:
-
It should include a reference to the issue ID in the first line of the commit, and a brief description of the issue, so everybody knows what this ID actually refers to without wasting to much time on following the link to the issue.
-
It should provide enough information for a reviewer to understand the changes and their relation to the rest of the code.
A good example:
Issue #190: Short summary of the issue
* One of the important changes
* Another important change
A (really) bad example:
Fixes #190
TODO: Review
Our development cycle is straightforward, we define a roadmap with milestones
for releases, and features that we want to include in these releases. The
roadmap is not public at the moment, but it's a committed project in our
community and we are working to make parts of it public in a way that can be
beneficial for everyone. Whenever a new release is close to be launched, we'll
announce it and detail what has changed since the latest version.
The channels we'll use to announce new releases are still being discussed, but
for now you can follow us <https://twitter.com/qiskit>_ on Twitter!
There are two main branches in the repository:
-
master- This is the development branch.
- Next release is going to be developed here. For example, if the current latest release version is r1.0.3, the master branch version will point to r1.1.0 (or r2.0.0).
- You should expect this branch to be updated very frequently.
- Even though we are always doing our best to not push code that breaks things, is more likely to eventually push code that breaks something... we will fix it ASAP, promise :).
- This should not be considered as a stable branch to use in production environments.
- The public interface could change without prior notice.
-
stable- This is our stable release branch.
- It's always synchronized with the latest distributed package, as for now, the package you can download from pip.
- The code in this branch is well tested and should be free of errors (unfortunately sometimes it's not).
- This is a stable branch (as the name suggest), meaning that you can expect stable software ready for production environments.
- All the tags from the release versions are created from this branch.