[yt-dev] .quantities issue

[Matthew Turk]

Hi Stephen,

On Fri, Feb 24, 2012 at 7:25 PM, Stephen Skory <s at skory.us> wrote:
> Hi all,
>
> when I was trying to work on Mike's latest halo finder problem, I
> tried swapping out the total_mass sum for a .quantities on this line:
>
> https://bitbucket.org/yt_analysis/yt/src/73fa0ace10e3/yt/analysis_modules/halo_finding/halo_objects.py#cl-2047
>
> but doing that seriously changed the answers. Digging a bit deeper I
> see that for some reason, the same value is being fed in twice (I'm
> using two cores) to mpi_allreduce, which gives the wrong total_mass
> out. I see different values going into mpi_allreduce, and the correct
> total_mass, when I use the original summing method. This has led me to
> conclude that the .quantities is not being done correctly here -
> there's something wrong with the multi-level parallelism here I
> think... or something. Does anyone have any ideas of what could be
> going on? Thanks!

I'm not sure I understand -- is something wrong with
*quantities-in-general*, or with the way it's being called in
halo_objects?  Can you investigate with a small dataset if the answer
changes based on manually calculating versus using quantities in
serial & parallel?

-Matt

>
> --
> Stephen Skory
> s at skory.us
> http://stephenskory.com/
> 510.621.3687 (google voice)
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