[yt-users] Projection Performance

[Sam Skillman]

Hi Rick,

For me, running on a single 2.93 GHz Xeon core, it
takes 9.818254e+02 seconds to project the LCL7 for unweighted density. With
the change I mention below, on 8 cores, this took the time down
to 1.796410e+02 seconds.  If you have a parallel file system this will
probably be a better speedup.

For the lightcone, you may benefit quite a lot by swapping out the quad
tree projection for the (for now) much more parallel overlap projection
method and running in parallel.  This works best for naturally domain
decomped simulations like the light cone.  Note this is only faster in
parallel.  The quad tree method is much faster in serial. You would do this
with:

pf.h.proj = pf.h.overlap_proj

after you've loaded the parameter file, and run your script (as is) with
mpirun -np N your_script.py --parallel

You can probably get decent speedup values for N = 32 or 64. There are some
scaling performance plots from yt about a year ago in the method paper.

I also might suggest forgetting about saving all of these through the plot
collection and instead just make all the projections first.  They will be
saved in the .yt files and can later be recalled in serial where you can
play around with the various figures.  It does this automatically so when
you try to load up a plot collection with a density projection, for
example, it will just read it in from the .yt file.  That way you can just
get all the adaptive projections and pan/zoom/export however you want
later.  Note that this method of saving the projections will only work for
the full box projections.  The region based projections are not currently
saved automatically.

Anyways, those are my two cents.
Sam





On Tue, May 1, 2012 at 6:15 PM, Richard P Wagner <rpwagner at sdsc.edu> wrote:

> Hi,
>
> I wanted to build a sequence of projections using various color maps along
> each axis. The data set I'm using the z = 0 one from the L7 simulation some
> of you are familiar with. Here's the paste of my current script:
>  http://paste.yt-project.org/show/2335/
>
> (The early sys.exit is deliberate.)
>
> Does anyone have an estimate of the time doing this projection serially
> should take? After two hours it was still going without having produced the
> first image. The same plots done on the z = 2.75 data took about 15 minutes
> (this data has about 1/5 the number of grids, though).
>
> I will also gladly take advice on better methods for the projections, or
> if the benefit to doing this in parallel is worth it.
>
> Thanks,
> Rick
>
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