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[Jan Stránský <question245380@xxxxxxxxxxxxxxxxxxxxx>]

Question #245380 on Yade changed:
https://answers.launchpad.net/yade/+question/245380

    Status: Open => Answered

Jan Stránský proposed the following answer:
Hello Hien,

for efficient extraction of 'old', 'new' and 'permamnent' interactions have
a look at python set [1]. Something like:

idsBegin = set((i.id1,i.id2) for i in interactionsBegin)
idsEnd = set((i.id1,i.id2) for i in interactionsEnd)
permanent = idsEnd & idsBegin # or idsEnd.intersection(idsBegin)
new = idsEnd - permanent # or idsEnd.difference(permanent)
lost = idsBegin - permanent # or idsBegin.difference(permanent)

cheers
Jan

[1] http://docs.python.org/2/library/sets.html



2014-03-12 15:01 GMT+01:00 Hien Nguyen <question245380@xxxxxxxxxxxxxxxxxxxxx
>:

> New question #245380 on Yade:
> https://answers.launchpad.net/yade/+question/245380
>
> Hello everybody,
> I want to ask a question about contact detection of two different states
> of the same specimen. Here is my problem:
> I have a saved model, named 'begin.xml', from this specimen, I apply a
> force and after certain number of iterations, I have the specimen named
> 'end.xml'.
> I want to detect the different interactions in 'begin.xml' and 'end.xml',
> I sort them into 3 types:
> 1. Permanent interactions: interaction that stays the same from 'begin' to
> 'end'
> 2. Newly formed interactions: interaction that is not available in
> 'begin', but appears in 'end'
> 3. Lost interactions: interaction that once was in 'begin' but in 'end'
> it's no longer available.
>
> And based on that sorting method, I want to extract information from those
> bodies like positions and forces of the both 'base' and 'end' state.
>  (position as x1, x2 and force as f, if interaction is not available, f=0)
>
>
> Here is what I drafted for my idea:
>
> O.load('end')
> for i in O.interactions:
>   x_1_end=O.bodies[i.id1].state.pos
>   x_2_end=O.bodies[i.id2].state.pos
>   f_end=i.phys.normalForce+i.phys.shearForce
>   O.load('begin')
>   for j in O.interactions:
>     if j.id1==i.id1 and j.id2==i.id2: # condition of the permanent
> interaction
>       x_1_begin=O.bodies[j.id1].state.pos
>       x_2_begin=O.bodies[j.id2].state.pos
>       f_begin=j.phys.nomalForce + j.phys.shearForce
>
>
> Till this point, this certainly handles the permanent interactions but I
> don't know how to continue with the lost and new interactions between
> 'begin' and 'end'. Maybe I might continue my script as:
>
>   elif j.id1==i.id1 and j.id2!=i.id2:
>       x_1_begin=O.bodies[j.id1].state.pos
>       x_2_begin=O.bodies[j.id2].state.pos
>       f_begin=j.phys.normalForce+i.phys.shearForce # of f=0 depends on
> 'new' or 'lost' conception
>   elif j.id1!=i.id1 and j.id2==i.id2:...
>   else:
>     continue
>
> But I'm not sure this should work (the condition seems silly but I haven't
> found another better one). So I have questions:
>
> 1. How to effectively discriminate those three types of interaction
> between two states I mentioned above. Most of all the *newly formed
> interaction* and the *lost interaction*.
> 2. In which manner YADE sorts the interactions when we loop all over them,
> I do:
> for i in O.interactions:
>   print i.id1, i.id2
> and I see the list is quite in random order, but I do the script again and
> list is still the same so I convince myself that YADE is using certain
> sorting method for such looping, is that true? Can you enlighten me on this
> point?
>
> Thanks in advance!
>
>
>
>
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