Pylops

* Added ``pylops.signalprocessing.Shift`` operator.
* Added option to choose derivative kind in
``pylops.avo.poststack.PoststackInversion`` and
``pylops.avo.prestack.PrestackInversion``
* Improved efficiency of adjoint of
``pylops.signalprocessing.Fredholm1`` by applying complex conjugation
to the vectors.
* Added `vsvp` to ``pylops.avo.prestack.PrestackInversion`` allowing
to use user defined VS/VP ratio.
* Added `kind` to ``pylops.basicoperators.CausalIntegration`` allowing
``full``, ``half``, or ``trapezoidal`` integration
* Fixed `_hardthreshold_percentile` in
``pylops.optimization.sparsity`` - Issue 249.
* Fixed r2norm in ``pylops.optimization.solver.cgls``

* Added ``pylops.optimization.solver.lsqr`` solver
* Added utility routine ``pylops.utils.scalability_test`` for scalability
tests when using ``multiprocessing``
* Added ``pylops.avo.avo.ps`` AVO modelling option and restructured
``pylops.avo.prestack.PrestackLinearModelling`` to allow passing any
function handle that can perform AVO modelling apart from those directly
available
* Added R-linear operators (when setting the property `clinear=False` of a
linear operator). ``pylops.basicoperators.Real``,
``pylops.basicoperators.Imag``, and ``pylops.basicoperators.Conj``
* Added possibility to run operators ``pylops.basicoperators.HStack``,
``pylops.basicoperators.VStack``, ``pylops.basicoperators.Block``
``pylops.basicoperators.BlockDiag``,
and ``pylops.signalprocessing.Sliding3D`` using ``multiprocessing``
* Added dtype to vector `X` when using ``scipy.sparse.linalg.lobpcg`` in
`eigs` method of ``pylops.LinearOperator``
* Use `kind=forward` fot FirstDerivative in
``pylops.avo.poststack.PoststackInversion`` inversion when dealing
with L1 regularized inversion as it makes the inverse problem more stable
(no ringing in solution)
* Changed `cost` in ``pylops.optimization.solver.cg``
and ``pylops.optimization.solver.cgls`` to be L2 norms of residuals
* Fixed ``pylops.utils.dottest.dottest`` for imaginary vectors and to
ensure `u` and `v` vectors are of same dtype of the operator

* Added ``pylops.signalprocessing.Sliding1D`` and
``pylops.signalprocessing.Patch2D`` operators
* Added ``pylops.basicoperators.MemoizeOperator`` operator
* Added decay and analysis option in ``pylops.optimization.sparsity.ISTA`` and
``pylops.optimization.sparsity.FISTA`` solvers
* Added `toreal` and `toimag` methods to ``pylops.LinearOperator``
* Make `nr` and `nc` optional in ``pylops.utils.dottest.dottest``
* Fixed complex check in ``pylops.basicoperators.MatrixMult``
when working with complex-valued cupy arrays
* Fixed bug in data reshaping in check in
``pylops.avo.prestack.PrestackInversion``
* Fixed loading error when using old cupy and/or cusignal

* Modified all operators and solvers to work with cupy arrays
* Added ``eigs`` and ``solver`` submodules to ``optimization``
* Added ``deps`` and ``backend`` submodules to ``utils``
* Fixed bug in ``pylops.signalprocessing.Convolve2D`` and
``pylops.signalprocessing.ConvolveND`` when dealing with
filters that have less dimensions than the input vector.

* Fixed import of ``pyfttw`` when not available in
``pylops.signalprocessing.ChirpRadon3D``

* Added ``pylops.signalprocessing.ChirpRadon2D`` and
``pylops.signalprocessing.ChirpRadon3D`` operators.
* Fixed bug in the inferred dimensions for regularization data creation
in ``pylops.optimization.leastsquares.NormalEquationsInversion``,
``pylops.optimization.leastsquares.RegularizedInversion``, and
``pylops.optimization.sparsity.SplitBregman``.
* Changed dtype of ``pylops.HStack`` to allow automatic inference from
dtypes of input operator.
* Modified dtype of ``pylops.waveeqprocessing.Marchenko`` operator to
ensure that outputs of forward and adjoint are real arrays.
* Reverted to previous complex-friendly implementation of
``pylops.optimization.sparsity._softthreshold`` to avoid division by 0.