CHANGELOG.md

3.12.0

• New FiniteSplitterWall structure.

3.11.0

• particlebeam and randominside_xyφ functions.

3.10.0

• It is now possible in timeseries! to evolve a particle until a certain boolean condition is met.

3.9.0

• It is now possible to create animations as gifs.

3.8.0

• Walls can have their normal vector automatically calculated, pointing to the left of the endpoint - startpoint.
• New function billiard_vertices that creates a billiard out of vertices.

3.7.0

• extrapolate is now mentioned in the documentation and has a docstring.

3.6.3

• Bugfix of timeseries function where if the dt was larger than the collision time, the returned timevector was wrong.

3.6

• Keyword particle_Kwargs of animate_evolution can now conveniently be nothing, in which case the particles are not plotted, only their trajectories.

3.5

• New function visited_obstacles!.
• 2D and 3D chaotic phase space volumes now in MushroomTools.

3.4

• Lyapunov computation and perturbation growth can now accept integer time (which means amount of collisions).

3.3

• Replaced all instances of pertubation with perturbation. A deprecation is thrown.

3.2

• New perturbation growth functions.

3.1

• law_of_refraction : new function that returns transmission and refraction functions based on Snell's law and refractive indices.
• Plenty of doc corrections.

3.0

Breaking changes

• Plotting functions now overload plot instead. There is no more plot_obstacle, plot_billiard and plot_particle. plot_boundarymap and animate_evolution remain the same though.
• construct is removed.
• boundarymap call signature and return values are reworked.

Enhancements / new features

• Brand new evolution animation function (replaced the old). It now animates in real-time!!! (you can use dt = Inf to obtain the old behavior). In addition it supports animating the evolution of multiple particles in parallel!!!
• New function timeseries creates the timeseries of the particle evolution in a billiard. This does pretty much what construct(evolve...) used to do.
• New obstacle: Ellipse.
• Much more robust propagation algorithm that is less prone to errors and "weird behaviors"!
• Test suite reworked almost from scratch: More tests, more specific tests, more robust tests, easier to debug tests!
• totallength is exported.
• plot(bd, x, y) (using the timeseries of timeseries) now also works for non-periodic billiards as well, for convenience.
• Automatic parallelization is now possible for some functions, given by the parallelize function.

Low-Level changes

These changes are not actually breaking, unless someone used the low-level interface. The docs also changed and much less than the low level interface is exposed.

• Renamed collisiontime to just collision, since now it returns both the time and the estimated collision point.

• Many low-level functions are not exported any more, for safety and because it didn't make much sense: normvalvec, distance, cellsize, ``propagate!, relocate!, resolvecollision!, periodicity!, specular! realangle. For the low level interface only propagate!, bounce!, collision and next_collision are exposed. Only bounce! is exposed as public API. The low level interface is still documented though.

• Change of the internal propagation algorithm:

  1. the function collision (previously collisiontime) returns both the time until collision as well as the collision point (most methods computed it already anyways).
  2. The timeprec and all those nonsense are removed. It is the duty of collision to return Inf if the particle is very close to the collision point (realangle uses accuracy, while for straight propagation the direction of travel is enough).
  3. The particle is then "teleported" to this point by setting its pos. For the case of magnetic propagation the velocity is propagated by the collision time. This brings very high accuracy, as the velocity vector is not multiplied with time and then added to the position vector.
  4. The distance is checked. If it has wrong sign, a relocation simply relocates the particle in the direction of the normalvec, for amount (1+eps())*distance.
  5. Specular reflection / periodicity is done.

• Renamed distancecheck to accuracy

v2.3

• Now you can write p.ω as well as p.omega for magnetic particles.
• New ispinned function that returns Bool of whether a particle is pinned or not. Also works with periodic billiards.

v2.2

• Standard billiards can now also be created with keyword arguments.
• Logo billiard is now exported by the function billiard_logo.

v2.1

• Better limits of axis for periodic rectangular billiards.
• Added some methods for high level functions (like e.g. evolve) that if not given a particle they pick on from randominside.
• Documentation improvements.
• Bug fix in the expressions for the chaotic phase space volume of mushrooms.

v2.0

New Features!

• 3 orders of magnitude performance gains on all functions!!!

  • Reduced a lot of allocations done all over the place. In most places allocations done are now exactly zero! ZEROOOOOOOOOOOO
  • Fixed many instances of broadcasting with static vectors (which is bad).
  • Utilized metaprogramming to manually unroll some loops.
  • If a billiard is periodic it is now known at compile time. This gives massive performance benefits in functions like evolve, which have to check if the collision occured with periodic walls.

• Symver will now be properly respected from 2.0 onwards.

• Automatic saving of animations to video via ffmpeg!!!

• Hexagonal periodic plotting.

• Lyapunov exponents for magnetic particles are now possible!

• Added boundary map computation function which works for any billiard and any particle. It assumes that the obstacles are sorted counter clockwise.

  • Added to_bcoords, totallength
  • Added plot_boundarymap that plots the boundary map and the obstacle boundaries.

• Added robust coordinate change transformation from 3D real space to 2D boundary space, see to_bcoords, from_bcoords and arclengths.

• Added two novel high-level functions that compute the phase-space portion an orbit covers as the particle evolves: boundarymap_portion and phasespace_portion.

• Added Poincare surface of section function, which computes intersections with arbitrary planes!

• It is now possible to affect many different obstacles during ray-splitting!

• Plotting is now available the moment the user does using PyPlot. Done through the Requires module. The function enableplotting() does not exist anymore!

• Re-organized all source code into a much more readable state, and as a result significantly reduced the total lines of code.

• added evolve function that simply deepcopies particle.

• Added convenience function to compute the mean collision time in a billiard.

• New low-level function bounce! that propagates a particle from one collision to the next. In essence does what evolve! does with t=1, but without creating a bunch of saving stuff. All high level functions use bounce!.

Syntax and other breaking changes

• Default colors for plotting have been changed (random obstacles are purple, particle orbit is "C0").
• [BREAKING] Overhauled what a "billiard table" is: Now, called simply Billiard is a dedicated struct that stores the obstacles as a tuple. This means that all functions do not accept a Vector{Obstacle} anymore but rather a Billiard.
• [BREAKING] timeprec now takes arguments timeprec(::Particle, ::Obstacle) to utilize better multiple dispatch and reduce code repetition.
• [BREAKING] realangle now only takes one intersection and simply returns the real angle.
• [BREAKING] animate_evolution now does not have ! at the end, because it deepcopies the particle.
• [BREAKING] Re-worked ray-splitting: We now use the RaySplitter struct. See docs.

---

v1.6.1

Updated the documentation to reflect the new changes of v1.6.0

v1.6.0 - WARNING: DOCUMENTATION NOT UPDATED. SEE v1.6.1

• [BREAKING] Function animate_evolution has been renamed to animate_evolution! to remind users that it mutates the particle.
• [BREAKING] FiniteWall has been renamed to InfiniteWall and works as before for convex billiards. A new type FiniteWall is introduced that can work for non-convex billiards.
  • FiniteWall has some extra fields for enabling this.
  • FiniteWall has a boolean field isdoor, that designates the given wall to be Door. This is used in escapetime.
• MASSIVE: Added function escapetime(p, bt) which calculates the escape time of a particle from a billiard table. The escape time is the time until the particle collides with a Door (any Door).
• animate_evolution! can create a new figure and plot the billiard table on user input. This happens by default.
• Bugfix: relocation in magnetic case was not adaptive (for the backwards method).
• MASSIVE: Added a Semicircle type! For both types of evolution!
  • added Bunimovich billiard billiard_bunimovich
  • added mushroom billiard billiard_mushroom

v1.5.0

• Added possibility to calculate the Lyapunov spectrum of a billiard system. Currently this is available only for Particles.
  • use the function lyapunovspectrum for the computation.
• Changed the relocating algorithm to be geometric. i.e. the time adjusting is done geometrically (self-multiplying the adjustment by 10 at each repeated step).
• Magnetic propagation and straight propagation now both use timeprec(T) (see below). For both cases the maximum number of geometric iterations is 1 (for the default value of timeprec(T).
• This timeprec cannot be used PeriodWall and RaySplitting obstacles with MagneticParticles because when magnetic and relocating forward you get extremely shallow angles and you need huge changes in time for even tiny changes in position.
  • For this special case the function timeprec_forward(T) is used instead. This function results to on average 3-5 geometric relocation steps.
• Fixed many issues and bugs.

v1.4.0

• All major types defined by DynamicalBilliards have been changed to parametric types with parameter T<:AbstractFloat.
  • The above makes the billiard table type annotation be bt::Vector{<:Obstacle{T}}) where {T<:AbstractFloat} instead of the old bt::Vector{Obstacle}.
• Particle evolution algorithm has fundamentally changed. The way the algorithm works now is described in the documentation in the Physics page.
  • This point with conjuction with the above made the package much faster.
• Positional argument warning of evolve!() has been changed to keyword argument.
• The raysplitting functions must always accept 3 arguments, even in the case of straight propagation. The best way is to have the third argument have a default value.
• All distance functions can now take a position as an argument (giving a particle simply passes the position).
• Removed redundant functions like magnetic2standard.
• The package is now precompiled.
• Tests have been restructured to be faster, more efficient, and use the @testset type of syntax.
• Documentation has been made more clear.

v1.3.0

Changelog will be kept from this version. See the releases page for info on previous versions.