yade-users team mailing list archive

[Luc Sibille <luc.sibille@xxxxxxxxxxxxxx>]

Hi Chiara,

  I give you below some references, I never spent time to read them, 
but I think you can find usefull information:

** General about algorithmic:
Knut, D.E. 1973 The art of computer programming, chap. 3, Sorting and 
Searching. Reading Mass, USA: Addison Wesley.

** General about algorithmic applied to DEM:
O'Connor, R. M. 1996 A distributed discrete element modeling environment 
- algorithms, implementation and applications. PhD Thesis, MIT, 
Cambridge, Massachusetts.

** Grid subdivision:
Allen, M.P. & Tildesley, D.J. 1987 computer simulations of liquids.

** Quicksort or Heapsort
see the reference above: O'Connor 1996.

If you want a code where you can make comparisons between detection by 
grid or detection from a quicksort there is SDEC (I think I made a 
mistake in my previous mail: quicksort is implemented in SDEC (with grid 
detection) and not the method "check everything with everything"). I 
imagine that there are other codes but I don't know them. The problem 
with SDEC is that you need Visual C++ to compile it (I never tried with 
another compiler so I don't know if it works, and I don't know also if 
it works with the new versions of Visual C++). If you want to try SDEC 
you need to ask the authorization to Frederic Donzé (Frederic.Donze at 
hmg.inpg.fr) but it should not be a problem.

  Good luck,

 Luc



chiara.modenese@xxxxxxxxx a écrit :
> Hi Luc,
>
> I will deal with a dynamic problem and the global geometry is expected 
> to change a lot during the simulation. 
> Could you suggest me some papers where 
> I can find an example in which the SPA was used? Or a reference where it is 
> said that this contact detection method is fast or that it is fast according to 
> a specific kind of problem? Do you know other DEM softwares that are using the 
> SAP?
>
> Many thanks,
>
> Chiara
>
> > ----Messaggio originale----
> > Da: luc.sibille@univ-
> nantes.fr
> > Data: 16/11/2009 17.58
> > A: <yade-users@xxxxxxxxxxxxxxxxxxx>
> > Ogg: 
> Re: [Yade-users] R: Re:  Contact detection
> > Hi!
> >
> >   I coming back again 
> about the contact detection, actually in SDEC 
> > there was the choice between a 
> contact detection by grid and the 
> > simplest method  were "every particles was 
> checked with every particles" 
> > because detection by grid is not always the 
> fastest method, that depends 
> > on what you are simulating:
> >
> > 1/ When the 
> global geometry of your problem is more or less constant 
> > during the whole 
> simulation (for instance: simulation of a triaxial 
> > compression on a dense 
> granular assembly) the detection by grid is quite 
> > good, because you build the 
> grid once at the beginning of the simulation 
> > and you use the same grid during 
> the whole simulation. In addition you 
> > don't have to update the list of the 
> neighbouring particles too often.
> > 2/ When the global geometry of your 
> problem is not really fixed (for 
> > instance an avalanche of particles in a very 
> open space: you don't know 
> > a priori were the avalanche will propagate) it is 
> not sure if the 
> > detection by grid will be good, because you will have to 
> update often 
> > the grid to follow the particles or you will have to make an 
> inital very 
> > large grid, whereas only few cells of the grid will be used at a 
> given 
> > time step for the detection.
> >
> > Chiara, I read your mails quite quickly 
> so I don't remember if you have 
> > specified the kind of simulation you want to 
> do, but in my opinion 
> > contact detection is good, but not always ;-)
> >
> > Best,
>
> >   Luc
> >
> > Janek Kozicki a écrit :
> > > Václav Šmilauer said:     (by the date 
> of Mon, 16 Nov 2009 09:46:52 +0100)
> > > > > > > In another words, Olivier (and 
> you) didn't bother to google out articles
> > > > > > > on that and thought he was the 
> smartest guy.
> > > > > > yeah. That time there was a LOT of other stuff to bother 
> about, than
> > > > > > colliders :) Paint me ashamed ;>
> > > > I am not saying you are 
> to be blamed, but Frederic, as supervisor of the
> > > > project, should have 
> managed that.
> > > I recall his point of view: SDEC has a lot slower collider 
> (IIRC:
> > > it was "check everything with everything"?. Some SDEC user could tell
>
> > > us). And so Frederic was very happy to see how much faster SAP is :)
>
> > --
> > Luc Sibille
> >
> > Université de Nantes - Laboratoire GeM UMR CNRS
> >
> > IUT de 
> Saint Nazaire
> > 58, rue Michel-Ange - BP 420
> > 44606 Saint-Nazaire Cedex, France
>
> > Tel: +33 (0)2 40 17 81 78
> >
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--
Luc Sibille

Université de Nantes - Laboratoire GeM UMR CNRS

IUT de Saint Nazaire
58, rue Michel-Ange - BP 420
44606 Saint-Nazaire Cedex, France

Tel: +33 (0)2 40 17 81 78