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Ids order in O.interactions

Asked by Hadda

Hi,

Is there any physical meaning/convention behind the order at which pairwise particles ids are appended to O.interactions?

I am interested in the default ones:

for i in O.interactions:
print i.id1, i.id2

I know that I can switch them when calling a specific existing contact, but it seems that the default values recorded in .phys do not change according to whether calling O.interactions[id1,id2] or O.interactions[id2,id1].

Any clues?

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Bruno Chareyre (bruno-chareyre) said : 		#1

Hi Nejib, there is no convention.
The fact that O.interactions[x,y] is the same as O.interactions[y,x] is a desirable feature, isn't it?
Both ways give the same interaction, hence the same particular ordering of ids.
Bruno

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Hadda (hadda) said : 		#2

Hi Bruno,

Thank you for your answer - I was just wondering if they were arranged such that one can know the force applied by id1 on id2 without using the normal.

Cheers

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Bruno Chareyre (bruno-chareyre) said : 		#3

The force is always applied by i.id1 on i.id2. No need to use the normal.
Does it answer your question?

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Hadda (hadda) said : 		#4

Thank you Bruno, yes it did!