When you encounter a problem please open an issue for it to the issue tracker.
If you have an idea for a new feature please open an Enhancement issue in the issue tracker. Opening an issue starts a discussion with the team about your idea, how it fits in with the project, how it can be implemented, etc.
Code review is done in the open and open to anyone. While only maintainers have access to merge commits, providing feedback on pull requests is very valuable and helpful. It is also a good mechanism to learn about the code base. You can view a list of all open pull requests here: https://github.com/Qiskit/qiskit-terra/pulls to review any open pull requests and provide feedback on it.
If you would like to contribute to the qiskit-terra project, but aren't sure of where
to get started, the
good first issue
label highlights items for people new to the project to work on. These are all issues that have
been reviewed by contributors and tagged as something a new contributor
should be able to develop a fix for. In other words it shouldn't require
intimate familiarity with qiskit-terra to develop a fix for the issue.
If you make a change, make sure you update the associated
docstrings and parts of the documentation under docs/apidocs that
corresponds to it. To locally build the terra specific documentation you
can run tox -edocs which will compile and build the documentation locally
and save the output to docs/_build/html. Additionally, the Docs CI job on
azure pipelines will run this and host a zip file of the output that you can
download and view locally.
If you have an issue with the combined documentation hosted at https://qiskit.org/documentation/ that is maintained in the Qiskit/qiskit. You can open a documentation issue if you see doc bugs, have a new feature that needs to be documented, or think that material could be added to the existing docs.
The way documentation is structured in terra is to push as much of the actual
documentation into the docstrings as possible. This makes it easier for
additions and corrections to be made during development because the majority
of the documentation lives near the code being changed. There are 3 levels of
pieces to the normal documentation structure in terra. The first is the rst
files in the docs/apidocs. These files are used to tell sphinx which modules
to include in the rendered documentation. The contain 2 pieces of information
an internal reference[1][2] to the module which can be used for internal links
inside the documentation and an automodule directive [3] used to parse the
module docstrings from a specified import path. For example, the dagcircuit.rst
file contains:
.. _qiskit-dagcircuit:
.. automodule:: qiskit.dagcircuit
:no-members:
:no-inherited-members:
:no-special-members:
The only rst file outside of this is qiskit.rst which contains the table of
contents if you're adding a new rst file for a new module's documentation make
sure to add it to the toctree [4] in that file.
The next level is the module level docstring. This docstring is at the module
level for the module specified in the automodule directive in the rst file.
If the module specified is a directory/namespace the docstring should be
specified in the __init__.py file for that directory. This module level
docstring starts to contain more details about the module being documented.
The normal structure to this module docstring is to outline all the classes and
functions of the public api that are contained in that module. This is typically
done using the autosummary directive[5] (or autodoc directives [3] directly
if the module is simple, such as in the case of qiskit.execute) The
autosummary directive is used to autodoc a list of different python elements
(classes, functions, etc) directly without having to manually call out the
autodoc directives for each one. This modulelevel docstring is a normally the
place you will want to provide a high level overview of what functionality is
provided by the module. This is normally done by grouping the different
components of the public API together into multiple subsections.
For example, continuing that dagcircuit module example from before the
contents of the module docstring for qiskit/dagcircuit/__init__.py would be:
"""
=======================================
DAG Circuits (:mod:`qiskit.dagcircuit`)
=======================================
.. currentmodule:: qiskit.dagcircuit
DAG Circuits
============
.. autosummary::
:toctree: ../stubs/
DAGCircuit
DAGNode
Exceptions
==========
.. autosummary::
:toctree: ../stubs/
DAGCircuitError
"""
(note this is just an example and the actual module docstring for the dagcircuit module might diverge from this)
The last level is the actual docstring for the elements listed in the module docstring. You should strive to document thoroughly all the public interfaces exposed using examples when necessary.
Note you can use any sphinx directive or rst formatting in a docstring as it
makes sense. For example, one common extension used is the jupyter-execute
directive which is used to execute a code block in jupyter and display both
the code and output. This is particularly useful for visualizations.
[1] http://docutils.sourceforge.net/docs/ref/rst/restructuredtext.html#reference-names [2] https://www.sphinx-doc.org/en/latest/usage/restructuredtext/roles.html#ref-role [3] http://www.sphinx-doc.org/en/master/usage/extensions/autodoc.html [4] https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#table-of-contents [5] https://www.sphinx-doc.org/en/master/usage/extensions/autosummary.html
The hosted documentation at https://qiskit.org/documentation/ covers the entire qiskit project, Terra is just one component of that. As such the documentation builds for the hosted version get built by the qiskit meta-package repository https://github.com/Qiskit/qiskit. When commits are merged to that repo the output of sphinx builds get uploaded to the qiskit.org website. Those sphinx builds are configured to pull in the documentation from the version of the qiskit elements installed by the meta-package at that point. For example, if the meta-package version is currently 0.13.0 then that will copy the documentation from terra's 0.10.0 release. When the meta-package's requirements are bumped then it will start pulling documentation from that new version. This means if API documentation is incorrect to get it fixed it will need to be included in a new release. Documentation fixes are valid backports for a stable patch release per the stable branch policy (see that section below).
During the build process the contents of terra's docs/apidocs/ repository gets
recursively copied into a shared copy of doc/apidocs/ in the meta-package
repository along with all the other elements. This means what is in the root of
docs/apidocs on terra at a release will end up on the root of
https://qiskit.org/documentation/apidoc/
We use GitHub pull requests to accept contributions.
While not required, opening a new issue about the bug you're fixing or the feature you're working on before you open a pull request is an important step in starting a discussion with the community about your work. The issue gives us a place to talk about the idea and how we can work together to implement it in the code. It also lets the community know what you're working on and if you need help, you can use the issue to go through it with other community and team members.
If you've written some code but need help finishing it, want to get initial feedback on it prior to finishing it, or want to share it and discuss prior to finishing the implementation you can open a Work in Progress pull request. When you create the pull request prefix the title with the [WIP] tag (for Work In Progress). This will indicate to reviewers that the code in the PR isn't in it's final state and will change. It also means that we will not merge the commit until it is finished. You or a reviewer can remove the [WIP] tag when the code is ready to be fully reviewed for merging.
Before you can submit any code we need all contributors to sign a contributor license agreement. By signing a contributor license agreement (CLA) you're basically just attesting to the fact that you are the author of the contribution and that you're freely contributing it under the terms of the Apache-2.0 license.
When you contribute to the Qiskit Terra 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 document is available for review as a PDF.
Note:
If your contribution is part of your employment or your contribution is the property of your employer, then you will likely need to sign a corporate CLA too and email it to us at qiskit@us.ibm.com.
When submitting a pull request and you feel it is ready for review, please ensure that:
- The code follows the code style of the project and successfully
passes the tests. For convenience, you can execute
toxlocally, which will run these checks and report any issues. - The documentation has been updated accordingly. In particular, if a function or class has been modified during the PR, please update the docstring accordingly.
- If it makes sense for your change that you have added new tests that cover the changes.
- Ensure that if your change has an end user facing impact (new feature, deprecation, removal etc) that you have added a reno release note for that change and that the PR is tagged for the changelog.
The changelog is automatically generated as part of the release process
automation. This works through a combination of the git log and the pull
request. When a release is tagged and pushed to github the release automation
bot looks at all commit messages from the git log for the release. It takes the
PR numbers from the git log (assuming a squash merge) and checks if that PR had
a Changelog: label on it. If there is a label it will add the git commit
message summary line from the git log for the release to the changelog.
If there are multiple Changelog: tags on a PR the git commit message summary
line from the git log will be used for each changelog category tagged.
The current categories for each label are as follows:
| PR Label | Changelog Category |
|---|---|
| Changelog: Deprecation | Deprecated |
| Changelog: New Feature | Added |
| Changelog: API Change | Changed |
| Changelog: Removal | Removed |
| Changelog: Bugfix | Fixed |
As important as the content of the change, is the content of the commit message describing it. The commit message provides the context for not only code review but also the change history in the git log. Having a detailed commit message will make it easier for your code to be reviewed and also provide context to the change when it's being looked at years in the future. When writing a commit message there are some important things to remember:
- Do not assume the reviewer understands what the original problem was.
When reading an issue, after a number of back & forth comments, it is often clear what the root cause problem is. The commit message should have a clear statement as to what the original problem is. The bug is merely interesting historical background on how the problem was identified. It should be possible to review a proposed patch for correctness from the commit message, without needing to read the bug ticket. bug ticket.
- Do not assume the code is self-evident/self-documenting.
What is self-evident to one person, might not be clear to another person. Always document what the original problem was and how it is being fixed, for any change except the most obvious typos, or whitespace only commits.
- Describe why a change is being made.
A common mistake is to just document how the code has been written, without describing why the developer chose to do it that way. By all means describe the overall code structure, particularly for large changes, but more importantly describe the intent/motivation behind the changes.
- Read the commit message to see if it hints at improved code structure.
Often when describing a large commit message, it becomes obvious that a commit should have in fact been split into 2 or more parts. Don't be afraid to go back and rebase the change to split it up into separate pull requests.
- Ensure sufficient information to decide whether to review.
When Github sends out email alerts for new pull request submissions, there is minimal information included, usually just the commit message and the list of files changes. Because of the high volume of patches, commit message must contain sufficient information for potential reviewers to find the patch that they need to look at.
- The first commit line is the most important.
In Git commits, the first line of the commit message has special significance. It is used as the default pull request title, email notification subject line, git annotate messages, gitk viewer annotations, merge commit messages, and many more places where space is at a premium. As well as summarizing the change itself, it should take care to detail what part of the code is affected.
In addition the first line of the commit message gets used as entries in the generated changelog if the PR is tagged as being included in the changelog. It's critically important that you write a clear and succinct summary lines.
- Describe any limitations of the current code.
If the code being changed still has future scope for improvements, or any known limitations, then mention these in the commit message. This demonstrates to the reviewer that the broader picture has been considered and what tradeoffs have been done in terms of short term goals vs. long term wishes.
- Include references to issues
If the commit fixes or is related to an issue make sure you annotate that in the commit message. Using the syntax:
Fixes #1234
if it fixes the issue (github will close the issue when the PR merges).
The main rule to follow is:
The commit message must contain all the information required to fully understand & review the patch for correctness. Less is not more.
When making any end user facing changes in a contribution we have to make sure we document that when we release a new version of qiskit-terra. The expectation is that if your code contribution has user facing changes that you will write the release documentation for these changes. This documentation must explain what was changed, why it was changed, and how users can either use or adapt to the change. The idea behind release documentation is that when a naive user with limited internal knowledege of the project is upgrading from the previous release to the new one, they should be able to read the release notes, understand if they need to update their program which uses qiskit, and how they would go about doing that. It ideally should explain why they need to make this change too, to provide the necessary context.
To make sure we don't forget a release note or if the details of user facing changes over a release cycle we require that all user facing changes include documentation at the same time as the code. To accomplish this we use the reno tool which enables a git based workflow for writing and compiling release notes.
Making a new release note is quite straightforward. Ensure that you have reno installed with::
pip install -U reno
Once you have reno installed you can make a new release note by running in your local repository checkout's root::
reno new short-description-string
where short-description-string is a brief string (with no spaces) that describes what's in the release note. This will become the prefix for the release note file. Once that is run it will create a new yaml file in releasenotes/notes. Then open that yaml file in a text editor and write the release note. The basic structure of a release note is restructured text in yaml lists under category keys. You add individual items under each category and they will be grouped automatically by release when the release notes are compiled. A single file can have as many entries in it as needed, but to avoid potential conflicts you'll want to create a new file for each pull request that has user facing changes. When you open the newly created file it will be a full template of the different categories with a description of a category as a single entry in each category. You'll want to delete all the sections you aren't using and update the contents for those you are. For example, the end result should look something like::
features:
- |
Introduced a new feature foo, that adds support for doing something to
``QuantumCircuit`` objects. It can be used by using the foo function,
for example::
from qiskit import foo
from qiskit import QuantumCircuit
foo(QuantumCircuit())
- |
The ``qiskit.QuantumCircuit`` module has a new method ``foo()``. This is
the equivalent of calling the ``qiskit.foo()`` to do something to your
QuantumCircuit. This is the equivalent of running ``qiskit.foo()`` on
your circuit, but provides the convenience of running it natively on
an object. For example::
from qiskit import QuantumCircuit
circ = QuantumCircuit()
circ.foo()
deprecations:
- |
The ``qiskit.bar`` module has been deprecated and will be removed in a
future release. Its sole function, ``foobar()`` has been superseded by the
``qiskit.foo()`` function which provides similar functionality but with
more accurate results and better performance. You should update your calls
``qiskit.bar.foobar()`` calls to ``qiskit.foo()``.You can also look at other release notes for other examples.
You can use any restructured text feature in them (code sections, tables, enumerated lists, bulleted list, etc) to express what is being changed as needed. In general you want the release notes to include as much detail as needed so that users will understand what has changed, why it changed, and how they'll have to update their code.
After you've finished writing your release notes you'll want to add the note
file to your commit with git add and commit them to your PR branch to make
sure they're included with the code in your PR.
After release notes have been added if you want to see what the full output of
the release notes. In general the output from reno that we'll get is a rst
(ReStructuredText) file that can be compiled by
sphinx. To generate the rst file you
use the reno report command. If you want to generate the full terra release
notes for all releases (since we started using reno during 0.9) you just run::
reno report
but you can also use the --version argument to view a single release (after
it has been tagged::
reno report --version 0.9.0
At release time reno report is used to generate the release notes for the
release and the output will be submitted as a pull request to the documentation
repository's release notes file
Building The release notes are part of the standard qiskit-terra documentation
builds. To check what the rendered html output of the release notes will look
like for the current state of the repo you can run: tox -edocs which will
build all the documentation into docs/_build/html and the release notes in
particulare will be located at docs/_build/html/release_notes.html
Please see the Installing Qiskit Terra from Source section of the Qiskit documentation.
Once you've made a code change, it is important to verify that your change does not break any existing tests and that any new tests that you've added also run successfully. Before you open a new pull request for your change, you'll want to run the test suite locally.
The easiest way to run the test suite is to use
tox. You can install tox
with pip: pip install -U tox. Tox provides several advantages, but the
biggest one is that it builds an isolated virtualenv for running tests. This
means it does not pollute your system python when running. Additionally, the
environment that tox sets up matches the CI environment more closely and it
runs the tests in parallel (resulting in much faster execution). To run tests
on all installed supported python versions and lint/style checks you can simply
run tox. Or if you just want to run the tests once run for a specific python
version: tox -epy37 (or replace py37 with the python version you want to use,
py35 or py36).
If you just want to run a subset of tests you can pass a selection regex to
the test runner. For example, if you want to run all tests that have "dag" in
the test id you can run: tox -epy37 -- dag. You can pass arguments directly to
the test runner after the bare --. To see all the options on test selection
you can refer to the stestr manual:
https://stestr.readthedocs.io/en/stable/MANUAL.html#test-selection
If you want to run a single test module, test class, or individual test method
you can do this faster with the -n/--no-discover option. For example:
to run a module:
tox -epy37 -- -n test.python.test_examples
or to run the same module by path:
tox -epy37 -- -n test/python/test_examples.py
to run a class:
tox -epy37 -- -n test.python.test_examples.TestPythonExamples
to run a method:
tox -epy37 -- -n test.python.test_examples.TestPythonExamples.test_all_examples
Alternatively there is a makefile provided to run tests, however this
does not perform any environment setup. It also doesn't run tests in
parallel and doesn't provide an option to easily modify the tests run.
For executing the tests with the makefile, a make test target is available.
The execution of the tests (both via the make target and during manual
invocation) takes into account the LOG_LEVEL environment variable. If
present, a .log file will be created on the test directory with the
output of the log calls, which will also be printed to stdout. You can
adjust the verbosity via the content of that variable, for example:
Linux and Mac:
$ cd out
out$ LOG_LEVEL="DEBUG" ARGS="-V" make test
Windows:
$ cd out
C:\..\out> set LOG_LEVEL="DEBUG"
C:\..\out> set ARGS="-V"
C:\..\out> make test
For executing a simple python test manually, we don't need to change
the directory to out, just run this command:
Linux and Mac:
$ LOG_LEVEL=INFO python -m unittest test/python/circuit/test_circuit_operations.py
Windows:
C:\..\> set LOG_LEVEL="INFO"
C:\..\> python -m unittest test/python/circuit/test_circuit_operations.py
Some tests require that you an IBMQ account configured. By default these
tests are always skipped. If you want to run these tests locally please
go to this
page and
register an account. Then you can either set the credentials explicitly
with the IBMQ_TOKEN and IBMQ_URL environment variables to specify
the token and url respectively for the IBMQ service. Alternatively, if
you already have a single set of credentials configured in your
environment (using a .qiskitrc) then you can just set
QISKIT_TESTS_USE_CREDENTIALS_FILE to 1 and it will use that.
How and which tests are executed is controlled by an environment
variable, QISKIT_TESTS:
| Option | Description | Default |
|---|---|---|
skip_online |
Skips tests that require remote requests. Does not require user credentials. | False |
run_slow |
It runs tests tagged as slow. | False |
It is possible to provide more than one option separated with commas.
Alternatively, the make test_ci target can be used instead of
make test in order to run in a setup that replicates the configuration
we used in our CI systems more closely.
To enforce a consistent code style in the project we use
Pylint and
pycodesytle
to verify that code contributions conform respect the projects
style guide. To verify that your changes conform to the style
guide you can run: tox -elint
Or using the makefile you can run:
make style
make lint
The documentation for Qiskit Terra is in the docs directory of Qiskit
repository. See this
repository for more information, however, the reference documentation is
auto-generated from the python docstrings throughout the code using
Sphinx. Please follow Google's Python
Style
Guide
for docstrings. A good example of the style can also be found with
sphinx's napolean converter
documentation.
The development cycle for qiskit-terra is all handled in the open using the project boards in Github for project management. We use milestones in Github to track work for specific releases. The features or other changes that we want to include in a release will be tagged and discussed in Github. As we're preparing a new release we'll document what has changed since the previous version in the release notes.
master:
The master branch is used for development of the next version of qiskit-terra. It will be updated frequently and should not be considered stable. The API can and will change on master as we introduce and refine new features.
stable/*branches: Branches understable/*are used to maintain released versions of qiskit-terra. It contains the version of the code corresponding to the latest release for that minor version on pypi. For example, stable/0.8 contains the code for the 0.8.2 release on pypi. The API on these branches are stable and the only changes merged to it are bugfixes.
When it is time to release a new minor version of qiskit-terra we will:
- Create a new tag with the version number and push it to github
- Change the
masterversion to the next release version.
The release automation processes will be triggered by the new tag and perform the following steps:
- Create a stable branch for the new minor version from the release tag
on the
masterbranch - Build and upload binary wheels to pypi
- Create a github release page with a generated changelog
- Generate a PR on the meta-repository to bump the terra version and meta-package version.
The stable/* branches should only receive changes in the form of bug
fixes.
End users of Qiskit need to know if a feature or an API they are using and rely on will still be supported by the software tomorrow. Users rely on existing features, knowing under which conditions the project can remove (or change in a backwards incompatible manner) a feature or API is important. To manage expectations the following policy is how API and feature deprecation and removal is handled by Qiskit:
-
Features, APIs or configuration options are marked deprecated in the code. Appropriate
DeprecationWarningclass warnings will be sent to the user. The deprecated code will be frozen and receive only minimal maintenance (just so that it continues to work as-is). -
A migration path will be documented for current users of the feature. This will be outlined in the both the release notes adding the deprecation and the release notes removing the feature at the completion of the deprecation cycle. In addition, if feasible the warning message will also include the migration path. A migration path might be "stop using that feature", but in such cases it is necessary to first judge how widely used and/or important the feature is to end users and decided an obsolescence date based on that.
-
An obsolescence date for the feature will be set. The feature must remain intact and working (although with the proper warning being emitted) in all releases pushed until after that obsolescence date. At the very minimum the feature (or API, or configuration option) should be marked as deprecated (and still be supported) for at least three months of linear time from the release date of the first release to include the deprecation warning. For example, if a feature were deprecated in the 0.9.0 release of terra, which was released on August 22, 2019, then that feature should still appear in all releases until at least November 22, 2019. Since releases do not occur at fixed time intervals this may mean that a deprecation warning may only occur in one release prior to removal.
Note that this delay is a minimum. For significant features, it is recommend that the deprecated feature appears for at least double that time. Also, per the stable branch policy, deprecation removals can only occur during minor version releases, they are not appropriate for backporting.
The proper way to raise a deprecation warning is to use the warn function
from the warnings module
in the python standard library. The warning category class
should be a DeprecationWarning. An example would be:
import warnings
def foo(input):
warnings.warn('The qiskit.foo() function is deprecated as of 0.9.0, and '
'will be removed no earlier than 3 months after that release '
'date. You should use the qiskit.bar() function instead.',
DeprecationWarning, stacklevel=2)One thing to note here is the stack_level kwarg on the warn() call. This
argument is used to specify which level in the call stack will be used as
the line initiating the warning. Typically stack_level should be set to 2
as this will show the line calling the context where the warning was raised.
In the above example it would be the caller of foo(). If you did not set this,
the warning would show that the warning was caused by the line in the foo()
function, which is not helpful for users when trying to determine the origin
of a deprecated call. This value may be adjust though depending on the call
stack and where warn() gets called from. For example, if the warning is always
raised by a private method that only has one caller stack_level=3 might be
appropriate.
You can refer to the Release Notes section for the process of creating a new release note. One thing to keep in mind for deprecation release notes though is that we need to clearly document a migration path in that release note. This should outline what the current deprecated behavior would look like and how users will need to update their code when that deprecated feature is removed. In addition it is also good to explain the reasoning behind why the change was being made. This provides context for users as to why they want to update their code using Qiskit. A simple example would be:
deprecations:
- |
The function ``qiskit.foo()`` has been deprecated. An alternative function
``qiskit.bar()`` can be used instead to provide the same functionality.
This alternative function provides the exact same functionality but with
better performance and more thorough validity checking.In addition the Changelog: Deprecation label should be applied to any PRs
adding deprecation warnings so that they are highlighted in the changelog for
the release.
When an obsolecense date has passed and it's been determined safe to remove a deprecated feature from Qiskit we need to have an upgrade note in the release notes. We can copy the migration path from the deprecation release note but we should also indicate that the feature was deprecated and in which release. For example, building off the example in the previous section, if that deprecation occurred in the 0.9.0 release which occurred on August 22, 2019 and the removal occurred in the hypothetical 0.11.0 release on December 2nd, 2019 the release note would look like:
upgrade:
- |
The previously deprecated function ``qiskit.foo()``, which was deprecated
in the 0.9.0 release, has been removed. The ``qiskit.bar()`` function
should be used instead. ``qiskit.bar()`` provides the exact same
functionality but with better performance and more thorough validity
checking.Pull requests that remove a deprecated function will need to be tagged with the
Changelog: Removal label so that they get highlighted in the changelog for
the release.
The stable branch is intended to be a safe source of fixes for high impact bugs and security issues which have been fixed on master since a release. When reviewing a stable branch PR we need to balance the risk of any given patch with the value that it will provide to users of the stable branch. Only a limited class of changes are appropriate for inclusion on the stable branch. A large, risky patch for a major issue might make sense. As might a trivial fix for a fairly obscure error handling case. A number of factors must be weighed when considering a change:
- The risk of regression: even the tiniest changes carry some risk of breaking something and we really want to avoid regressions on the stable branch
- The user visible benefit: are we fixing something that users might actually notice and, if so, how important is it?
- How self-contained the fix is: if it fixes a significant issue but also refactors a lot of code, it's probably worth thinking about what a less risky fix might look like
- Whether the fix is already on master: a change must be a backport of a change already merged onto master, unless the change simply does not make sense on master.
When backporting a patch from master to stable we want to keep a reference to the change on master. When you create the branch for the stable PR you can use:
$ git cherry-pick -x $master_commit_id
However, this only works for small self contained patches from master. If you need to backport a subset of a larger commit (from a squashed PR for example) from master this just need be done manually. This should be handled by adding:
Backported from: #master pr number
in these cases, so we can track the source of the change subset even if a strict cherry pick doesn't make sense.
If the patch you're proposing will not cherry-pick cleanly, you can help by resolving the conflicts yourself and proposing the resulting patch. Please keep Conflicts lines in the commit message to help review of the stable patch.
Bugs or PRs tagged with stable backport potential are bugs
which apply to the stable release too and may be suitable for
backporting once a fix lands in master. Once the backport has been
proposed, the tag should be removed.
The PR against the stable branch should include [Stable]
in the title, as a sign that setting the target branch as stable was not
a mistake. Also, reference to the PR number in master that you are
porting.