- Update to 4.2.1:
This release provides a number of corrections for the ESPResSo
4.2 line. We recommend that this release be used for all
production simulations. The interface has not been changed
between ESPResSo 4.2.0 and 4.2.1. However, some bugs were
discovered which can affect simulation results. No further bug
fix releases will be provided for the 4.2 line.

Added functionality
-------------------

* P3M and DipolarP3M can now be used with the hybrid
decomposition cell system with 1 MPI rank (#4678).
* Lattice-Boltzmann can now be used with the N-square and
hybrid decomposition cell systems with 2 or more MPI ranks
(#4676).

Changed requirements
--------------------
* The nbconvert version requirement was bumped to 6.5.1 to
patch an XSS vulnerability (#4658).

Improved documentation
----------------------
* The user guide now documents how to improve the
reproducibility of simulations that have checkpointing
enabled (#4677).
* The user guide now reflects that the lattice-Boltzmann
profile observables can be used in parallel (#4583).
* The active matter tutorial now uses an adequate engine
dipole for the swimmer particle (#4585).
* The error analysis tutorials have been improved (#4597).
* The tutorials can now be used in VS Code Jupyter (both the
desktop and web versions) and the mathematical formula are
now correctly displayed (#4531).
* All ESPResSo-specific CMake options are now documented in
the installation chapter of the user guide (#4608).
* Python package installation instructions no longer feature
package version numbers; instead, `requirements.txt` is used
as a constraint file (#4638).
* MMM1D algorithms now properly document their parameter names
(#4677).
* Reaction methods now cite the relevant literature (#4681).
* Caveats for chain analysis methods are now documented
(#4698).
* Minor formatting issues in Sphinx and typos in Python
docstrings were addressed (#4608).

Interface changes
-----------------
* A new boolean property
`System.virtual_sites.override_cutoff_check` was introduced
to allow disabling the cutoff range checks from virtual
sites (#4623).

Removed functionality
---------------------
* The unused and untested `Analysis.v_kappa()` method was
removed (#4534).

Improved testing
----------------
* Improve unit testing of core functionality: P3M, MMM1D, OIF,
virtual sites, script interface factory (#4631).

Bug fixes
---------
* The checkpointing mechanism now properly restores the
particle quaternion and all derived quantities (#4637).
Release 4.2.0 introduced a regression that caused checkpoint
files to overwrite the particle quaternion/director by a
unit vector pointing along the z direction, when the
`DIPOLES` feature was part of the myconfig file. This lead
to incorrect trajectories when reloading a simulation from
a checkpoint file, if the particle director played a role in
the simulation (ex: relative virtual sites, Gay-Berne
potential, anisotropic particles, active particles, etc.).
In addition, the angular velocity in body frame was restored
with the wrong orientation. Since the default myconfig file
contains `DIPOLES`, most ESPResSo users were affected.
* The checkpointing mechanism now properly restores LB
boundaries (#4649). Release 4.2.0 introduced a regression
where reloading LB populations would accidentally reset LB
boundary flags.
* The checkpointing mechanism now restores P3M and DipolarP3M
solvers without triggering a re-tune (#4677). In previous
releases, the checkpointing code would automatically re-tune
these algorithms during a reload, causing tiny deviations in
the forces that were problematic for trajectory
reproducibility.
* Brownian dynamics now integrates the rotational dynamics of
rotatable particles whose position is fixed in 3D space
(#4548).
* Langevin dynamics now properly integrates particles with
anisotropic friction (#4683, #4690).
* A regression that caused virtual sites to incorrectly count
their image box when crossing a periodic boundary has been
fixed (#4564, #4707).
* Particles can no longer be created or updated with a
negative mass or a null mass (#4679).
* Particles created without a user-specified type can now
participate in reactions (#4589).
* When a Monte Carlo displacement move is rejected, the
original particle velocity is now restored (#4589).
* Reaction methods now raise an exception when accidentally
calling `method.reaction(steps=20)` instead of
`method.reaction(reaction_steps=20)` (#4666). Since 4.2.0
the `steps` argument was ignored, in which case the default
value `reaction_steps=1` would used by the core. Note that
in the next minor release of ESPResSo, the `reaction_steps`
argument will be renamed to `steps`.
* Reaction methods now rebuild the list of free particle ids
every time `WidomInsertion::calculate_particle_insertion_potential_energy()`
and `ReactionAlgorithm::do_reaction()` are called (#4609).
This was needed to allow multiple concurrent reactions, as
well as avoiding subtle bugs when both the user and a
reaction method tried to create a new particle with an id
that used to belong to a deleted particle.
* When all particles are cleared, the reaction methods type
map is now also cleared (#4645). In the past, it was
possible to attempt a reaction on particles that had just
been cleared from the system, which would raise an
exception. This bug affected all ESPResSo releases since
4.0.
* The `System.part.pairs()` method now returns the correct
particle pairs when particle ids aren't both contiguous and
starting from 0 (#4628). The regression was introduced in
release 4.2.0.
* The auto-exclusions feature no longer adds spurious
exclusions to particle ids in the range [1, distance]
(#4654). This bug would potentially break the physics of the
system and potentially raise an exception in a system with
non-contiguous particle ids. This regression was introduced
in release 2.2.0b.
* The structure factor analysis code no longer double-counts
particles when the same particle type is provided twice
(#4534).
* The minimal distance distribution analysis code no longer
has an arbitrary cutoff distance when the simulation box is
aperiodic (open boundaries); this would cause spurious
artifacts to appear in the histogram at
`r = np.sum(system.box_l)` when particles were further apart
than this arbitrary distance (#4534).
* The cluster analysis functions are now disabled for systems
with Lees-Edwards periodic boundaries, since the cluster
analysis position wrapping code doesn't properly handle the
shear offset (#4698).
* The chain analysis methods now raise an error when the
number of chains or beads per chain is invalid (#4708).
* The observable tests now longer rely on deprecated numpy
options that were removed in numpy 1.24 (#4635).
* The visualizer `*_arrows_type_materials` options now have an
effect on arrow materials (#4686).
* The visualizer exception handling mechanism has been made
less brittle (#4686).
* The visualizer no longer raises exception when the optional
dependency `freeglut` isn't installed (#4691).
* The visualizer can randomly freeze when using collision
detection or bond breakage; a temporary workaround has been
introduced that fixes the issue for simulations that use
only 1 MPI rank (#4686).
* The `__dir__()` method of script interface objects no longer
raises an exception (#4674).
* Compilation and testsuite issues involving missing or
incorrect feature guards were addressed (#4562, #4648).
* The build system no longer silently ignores invalid external
feature definitions in `myconfig.hpp` and CMake files
(#4608). This issue would only affect feature developers,
as well as users of very old compilers, and would lead to
ESPResSo builds missing features.

Under the hood changes
----------------------
* The Clang 14 and AppleClang 14 compilers are now supported
(#4601).
* Several Clang 14 compiler diagnostics have been addressed
(#4606).
* Boost 1.81 and later versions are now supported (#4655).
* Compiler errors on non-x86 architectures were addressed
(#4538).
* Test tolerances were adjusted for non-x86 architectures
(#4708).
* The pypresso script now prints a warning when running with
MCA binding policy "numa" on NUMA architectures that are not
supported in singleton mode by Open MPI 4.x (#4607).
* The config file generator has been rewritten to properly
handle external features and compiler errors (#4608).
* Security hardening for GitHub Workflows (#4577, #4638) and
Codecov (#4600).
* Deployment of the user guide to GitHub Pages now relies on
cloud providers to fetch JavaScript dependencies (#4656).
- Removed upstreamed patches:
- fix-broken-fft-check.patch
- boost-1.74.patch
- numpy-1.24.patch
- rpath.patch
- missing_size_t.patch
- hdf5.patch
- setuptools.patch