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Mention that particles with invalid ids are removed by default and be explicit about allowed ranges #4807

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Mention that particles with invalid ids are removed by default and be explicit about allowed ranges #4807

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9572fae
Mention that particles with invalid ids are removed by default and be…
atmyers Nov 19, 2025
2dff451
Update Docs/sphinx_documentation/source/Particle.rst
atmyers Nov 19, 2025
43221c8
Update Docs/sphinx_documentation/source/Particle.rst
atmyers Nov 19, 2025
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8 changes: 7 additions & 1 deletion Docs/sphinx_documentation/source/Particle.rst
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Expand Up @@ -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:

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