[FLASH-USERS] Particle counts and "seeing" particles.

[Klaus Weide]

On Fri, 21 Nov 2014, Joshua Wall wrote:

> Users,
> 
>    I'm currently making sink particles by calling pt_sinkCreateParticle
> while Flash is running to input sinks on the fly during a simulation.
> However I've noticed that this doesn't appear to update the "global" number
> of particles in the simulation, and I'm having trouble tracking down what I
> need to call to do this (and to assure myself I haven't missed anything
> else during sink creation). Are the two particle types completely separate,
> or should I be calling other subroutines to ensure everything is properly
> synced up somewhere in the background?
> 
>   I should note the sinks appear properly, as I can see them in the HDF5
> and in plots in yt (thanks to John help). But Flash reports the number of
> global particles is zero during a run after I add them.

I believe the following describes the behavior of sink particles,
but I may be mising some details.

Sink particles are maintained by the Particles unit (code under 
ParticlesMain/active/Sink/) in their own  data structure, separate from 
the general FLASH "particles" array.  Updating of the latter from the 
former happens only "when needed", which mean it happens as part if I/O,
right before the FLASH particles are written to a particle or checkpoint 
file; this way, the files will countain an up to date state of the sink
particles.

See the 

    call Particles_sinkSyncWithParticles(sink_to_part=.true.)

in IO_writeParticles.F90.

I assume that you could add calls to Particles_sinkSyncWithParticles in
other places if, for some reason, you want the FLASH particles to
contain  an accurate and up to date copy of the sink particle information.

Klaus