Re: galaxy collision demo

From: Sander Valcke <Sander.Valcke_at_UGent.be>
Date: Wed, 23 Sep 2009 09:15:56 +0200

Just a quick note to those concerned (Dimitry also): you can find
example routines on how to read Gadget IC files in the Analysis
directory. Mind that this only works for snapshot format 1. This is fine
for anyone not planning to ever add any custom IO blocks to the
snapshots written by their Gadget code. For people expecting to add
custom data to the snapshots I would recommend using snapshot format 2,
as it's (much more) flexible. If there were examples to read snapshot 2
formats in Analysis I would recommend not using the snapshot format 1 at
all :-), there is no downside to using the format 2.

When you are anxious to see what's in your snapshots and don't want to
wait till you've cooked up a reading program (and/or to check if reading
the IC is done properly) there are a good number of tools available
already: ifrit, splash, hyplot (see signature), ... try taking a look
around at http://www.astrosim.net/code/doku.php. No need for each gadget
user to reinvent the wheel ;-)

Sander

Douglas/Lesli Summerstay wrote:
> We are developing a method for automatically selecting key-frames in
> data that contain the most information about how the evolution of
> particle data is happening, that best describe the animation (I am at
> the University of Maryland, working with Amitabh Varshney). To do
> this, I need scientifically interesting particle data in four
> dimensions. We thought this data would be just what we needed
> (especially since there are already "keyframes" evenly spaced in time
> that others have published on the web to compare it to), but so far I
> haven't been successful in generating it.
> I can write a program in C++ or Matlab to read the snapshot files,
> since they're described pretty well in the documentation.
> I would be very grateful if you could find a way to send me those
> snapshots.
>
> Douglas
>
> On Mon, Sep 21, 2009 at 11:26 AM, Jay Billings
> <jayjaybillings_at_gmail.com <mailto:jayjaybillings_at_gmail.com>> wrote:
>
> Douglas,
>
> I had compiled FFTW wrong in my case, but I don't know if this is
> the problem with yours. You could probably track your problem down
> quickly with a debugger or some print statements.
>
> I could supply you with some snapshots, but I have to ask why need
> it? Also, do you have the capability to read to read the
> snapshots? I don't mean for the first question to sound offensive;
> I just need to be sure that you don't need it for a homework
> problem or something.
>
> Jay
>
>
> On Mon, Sep 21, 2009 at 11:06 AM, Douglas/Lesli Summerstay
> <dsummerstay_at_gmail.com <mailto:dsummerstay_at_gmail.com>> wrote:
>
> Jay,
> I imagine it may be, as you say, some kind of compilation
> error on my part. It is running, using up CPU, but not
> generating even the first snapshot in galaxy/ . Any idea the
> nature of the error you had? Or suggestions on how to track it
> down?
> Unfortunately I need the 3D position data, not just the video.
> Thanks again.
>
> Douglas
>
>
> On Mon, Sep 21, 2009 at 10:51 AM, Jay Billings
> <jayjaybillings_at_gmail.com <mailto:jayjaybillings_at_gmail.com>>
> wrote:
>
> Douglas,
>
> You are correct that you should see a snapshot at t=0 for
> the test problem. Did you look in the galaxy/ directory?
> The snapshots are stored there.
>
> The test problem with default settings only outputs six or
> seven snapshot files from t=0 to t=3.0. I'm a bit
> concerned that it has taken "days" without creating any
> snapshot files; that test problem runs in 15 minutes on my
> quad core machine and in about an hour on my old P4. When
> I first started working with Gadget2 I encountered a
> similar problem to yours and it turned out to be a compile
> error.
>
> If you are only interested in videos, you might check out
> my youtube page: http://www.youtube.com/jayjaybillings .
> These are videos of a different simulation.
>
> Jay
>
> On Mon, Sep 21, 2009 at 10:39 AM, Douglas/Lesli Summerstay
> <dsummerstay_at_gmail.com <mailto:dsummerstay_at_gmail.com>> wrote:
>
> I am trying to run the galaxy collision sample and had
> a few questions:
> I am trying to run it on a single processor. How long
> should I expect to wait before seeing any output
> snapshot files? (I am using the default
> parameter file.) I left it running for days without
> seeing any snapshot files created. This seems odd
> because the first snapshot is supposed to be created
> at time 0. Any idea why no snapshot files are being
> created? Alternately, could anyone run this simulation
> and make the snapshot files available to me?
> Are the pictures of colliding galaxies on the Gadget
> site
> (http://www.mpa-garching.mpg.de/gadget/collision/index.html )
> from this simulation?
>
> Thanks for your help.
>
> --
> http://dsummerstay.googlepages.com
>
>
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-- 
--------------------------------------------------
| Sander Valcke                                  |
| Sterrenkundig Observatorium, Universiteit Gent |
| Krijgslaan 281 S9, B-9000 Gent, Belgium        |
| phone +32-9-264-4796  |  fax +32-9-264-4989    |
| https://sourceforge.net/projects/hyplot/       |
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Sometimes the best medicine is to stop taking something.
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Received on 2009-09-23 09:10:40

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