Sparse

-------------------

* Fix :obj:`ValueError` on :obj:`sparse.dot` with extremely small values. (:issue:`398`, :pr:`399`)

-------------------

* Improve the performance of :obj:`sparse.dot`. (:issue:`331`, :pr:`389`, thanks :ghuser:`daletovar`)
* Added the :obj:`COO.swapaxes` method. (:pr:`344`, thanks :ghuser:`lueckem`)
* Added multi-axis 1-D indexing support. (:pr:`343`, thanks :ghuser:`mikeymezher`)
* Fix :obj:`outer` for arrays that weren't one-dimensional. (:issue:`346`, :pr:`347`)
* Add ``casting`` kwarg to :obj:`COO.astype`. (:issue:`391`, :pr:`392`)
* Fix for :obj:`COO` constructor accepting invalid inputs. (:issue:`385`, :pr:`386`)

-------------------

* Fixed a bug where converting an empty DOK array to COO leads
to an incorrect dtype. (:issue:`314`, :pr:`315`)
* Change code formatter to black. (:pr:`284`)
* Add :obj:`COO.flatten` and :obj:`sparse.outer`. (:issue:`316`, :pr:`317`).
* Remove broadcasting restriction between sparse arrays and dense arrays.
(:issue:`306`, :pr:`318`)
* Implement deterministic dask tokenization. (:issue:`300`, :pr:`320`, thanks
:ghuser:`danielballan`)
* Improve testing around densification (:pr:`321`, thanks
:ghuser:`danielballan`)
* Simplify Numba extension. (:pr:`324`, thanks :ghuser:`eric-wieser`).
* Respect ``copy=False`` in ``astype`` (:pr:`328`, thanks :ghuser:`eric-wieser`).
* Replace linear_loc with ravel_multi_index, which is 3x faster. (:pr:`330`,
thanks :ghuser:`eric-wieser`).
* Add error msg to tensordot operation when ``ndim==0`` (:issue:`332`,
:pr:`333`, thanks :ghuser:`guilhermeleobas`).
* Maintainence fixes for Sphinx 3.0 and Numba 0.49, and dropping support for
Python 3.5. (:pr:`337`).
* Fixed signature for :obj:`numpy.clip`.

------------------

* Fixed a bug where indexing with an empty list could lead
to issues. (:issue:`281`, :pr:`282`)
* Change code formatter to black. (:pr:`284`)
* Add the :obj:`diagonal` and :obj:`diagonalize` functions.
(:issue:`288`, :pr:`289`, thanks :ghuser:`pettni`)
* Add HTML repr for notebooks. (:pr:`283`, thanks :ghuser:`daletovar`)
* Avoid making copy of ``coords`` when making a new :obj:`COO`
array.
* Add stack and concatenate for GCXS. (:issue:`301`, :pr:`303`, thanks
:ghuser:`daletovar`).
* Fix issue where functions dispatching to an attribute access wouldn't
work with ``__array_function__``. (:issue:`308`, :pr:`309`).
* Add partial support for constructing and mirroring :obj:`COO` objects to
Numba.

------------------

This release switches to Numba's new typed lists, a lot of
back-end work with the CI infrastructure, so Linux, macOS
and Windows are officially tested. It also includes bug fixes.

It also adds in-progress, not yet public support for the GCXS
format, which is a generalisation of CSR/CSC. (huge thanks to
:ghuser:`daletovar`)

* Fixed a bug where an array with size == 1 and nnz == 0
could not be broadcast. (:issue:`242`, :pr:`243`)
* Add ``std`` and ``var``. (:pr:`244`)
* Move to Azure Pipelines with CI for Windows, macOS and
Linux. (:pr:`245`, :pr:`246`, :pr:`247`, :pr:`248`)
* Add ``resize``, and change ``reshape`` so it raises a
``ValueError`` on shapes that don't correspond to the
same size. (:issue:`241`, :issue:`250`, :pr:`256`
thanks, :ghuser:`daletovar`)
* Add ``isposinf`` and ``isneginf``. (:issue:`252`, :pr:`253`)
* Fix ``tensordot`` when nnz = 0. (:issue:`255`, :pr:`256`)
* Modifications to ``__array_function__`` to allow for sparse
XArrays. (:pr:`261`, thanks :ghuser:`nvictus`)
* Add not-yet-public support for GCXS. (:pr:`258`, thanks :ghuser:`daletovar`)
* Improvements to ``__array_function__``. (:pr:`267`, :pr:`272`, thanks
:ghuser:`crusaderky`)
* Convert all Numba lists to typed lists. (:pr:`264`)
* Why write code when it exists elsewhere? (:pr:`277`)
* Fix some element-wise operations with scalars. (:pr:`278`)
* Private modules should be private, and tests should be in the package.
(:pr:`280`)

------------------

This is a release that adds compatibility with NumPy's new
``__array_function__`` protocol, for details refer to
`NEP-18 <http://www.numpy.org/neps/nep-0018-array-function-protocol.html#coercion-to-a-numpy-array-as-a-catch-all-fallback>`_.

The other big change is that we dropped compatibility with
Python 2. Users on Python 2 should use version 0.6.0.

There are also some bug-fixes relating to fill-values.

This was mainly a contributor-driven release.

The full list of changes can be found below:

* Fixed a bug where going between :obj:`sparse.DOK` and
:obj:`sparse.COO` caused fill-values to be lost.
(:issue:`225`, :pr:`226`).
* Fixed warning for a matrix that was incorrectly considered
too dense. (:issue:`228`, :pr:`229`)
* Fixed some warnings in Python 3.7, the fix was needed.
in preparation for Python 3.8. (:pr:`233`, thanks :ghuser:`nils-werner`)
* Drop support for Python 2.7 (:issue:`234`, :pr:`235`, thanks
:ghuser:`hugovk`)
* Clearer error messages (:issue:`230`, :issue:`231`, :pr:`232`)
* Restructure requirements.txt files. (:pr:`236`)
* Support fill-value in reductions in specific cases. (:issue:`237`, :pr:`238`)
* Add ``__array_function__`` support. (:pr:`239`, thanks, :ghuser:`pentschev`)
* Cleaner code! (:pr:`240`)