[FLASH-USERS] Particles_sinkSyncWithParticles

[Klaus Weide]

On Wed, 26 Apr 2017, Joshua Wall wrote:

> So my question is basically, should Particles_sinkSyncWithParticles be
> modified to include the BLK_PART_PROP
> in the call to Grid_sortParticles when TYPE_PART_PROP is defined as seen in
> other sections of the code? Doing
> so in my case seems to fix a problem where sinks and a second particle type
> appear to get their places exchanged in the particles array after a
> particle file is written (which calls Particles_sinkSyncWithParticles).

Hello Josh,

After reviewing the code of Grid_sortParticles.F90, I believe that the 
answer is: yes, Particles_sinkSyncWithParticles should be modified as
you have proposed.

Grid_sortParticles isn't really a general-purpose sorting routine - one 
cannot just sort on any attribute. In practice, attrib1 pretty much has to 
be BLK_PART_PROP, and attrib2 should be TYPE_PART_PROP if present.

(The likely reason for passing these as arguments instead of hardwiring
them is that Grid_sortParticles may be used for other data elements than
particles (e.g., rays, protons), and those can use different index 
values.)

So the
  call Grid_sortParticles(particles,NPART_PROPS,pt_numLocal,NPART_TYPES, &
       pt_maxPerProc,particlesPerBlk,TYPE_PART_PROP)
is basically invalid, but happens to work, more or less, without invalid 
array references as long as for all particle type attribute values T:
     0 < int(T) < number of blocks on local proc  .

Klaus