diff --git a/Docs/sphinx_documentation/source/Particle.rst b/Docs/sphinx_documentation/source/Particle.rst index 9499d08e5c..d56824121e 100644 --- a/Docs/sphinx_documentation/source/Particle.rst +++ b/Docs/sphinx_documentation/source/Particle.rst @@ -48,7 +48,13 @@ the creation of particle initial conditions in parallel. In storing these identifying numbers, 39 bits are devoted to the `id`, allowing approximately 550 billion possible *local* `id` numbers, and 24 bits are used to store the `cpu`, allowing about 16.8 million unique (MPI) processes. -One bit is devoted to mark a particle valid or invalid. + +One bit is devoted to mark a particle valid or invalid. This is often used to remove particles from a +simulation. During :cpp:`Redistribute()`, particles with +invalid ids are removed from the simulation by default, although this behavior is customizable. Particles +with invalid ids are also not written out during plotfile writes or checkpoint / restart operations. +The allowed values for :cpp:`p.id()` are `0` to `2**39 - 1`, and the allowed values for :cpp:`p.cpu()` are +`0` to `2**24 - 1`. To pack and unpack these numbers, one uses the following syntax: