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[Bruno Chareyre <question682290@xxxxxxxxxxxxxxxxxxxxx>]

Question #682290 on Yade changed:
https://answers.launchpad.net/yade/+question/682290

Bruno Chareyre proposed the following answer:
I tried again with yadedaily (2018.02b-290bf6a54e~xenial), the results
are correct again.

@Luc, can't you try on a different computer to be sure we are on the
same page? I can't imagine that compiler options change the behavior of
bitwise operators...

@Jan, 
> "by luck" because avoidSelfInteractionMask is defined as static
Interesting... I wonder why it was defined static at all (probably off-topic though).

Jan's script made me realize my mistake, correct list in #12 was:
- if you set avoidSelf=1 you kill the 1-1 and 3-3 interactions.
- if you set avoidSelf=2 you kill the 2-2 and 3-3 interactions.
- if you set avoidSelf=3 you kill 1-1, 2-2, and 3-3; only 3-1 and 3-2 are left.

Below is a modified script which will not break python interpreter (and
is Python3 friendly). Note the explicit call to collider and
interactions.all() to get virtual interactions.

###
# mask values, "colors"
mb,mg,mr = 0b10, 0b01, 0b11
# mask to string dict
m2c = {mb:"b", mg:"g", mr:"r"}
# testing spheres, 2 of each color
sb1 = sphere((0,0,0),1,mask=mb)
sb2 = sphere((0,0.1,0),1,mask=mb)
sg1 = sphere((0.1,0,0),1,mask=mg)
sg2 = sphere((0,0,0.1),1,mask=mg)
sr1 = sphere((-0.1,0,0),1,mask=mr)
sr2 = sphere((0,-0.1,0),1,mask=mr)
O.bodies.append((sb1,sb2,sg1,sg2,sr1,sr2))
#
collider.avoidSelfInteractionMask = 0b00
collider.boundDispatcher.__call__()
collider.__call__()

idss = [(i.id1,i.id2) for i in O.interactions.all()] # id couples for each interaction
bss = [[O.bodies[i] for i in ids] for ids in idss] # body couple of each interaction
mss = [[b.mask for b in bs] for bs in bss] # mask couple of each interaction
mss = [tuple(sorted(ms)) for ms in mss] # make the mask couple of type tuple (needs by set below). Also sort it for proper deletion of duplicates
mss = set(mss) # make the entries unique (i.e. deleting duplicates)
css = ["".join(m2c[m] for m in ms) for ms in mss] # convert mask couples to strings
css.sort() # sort the result
css = " ".join(css) # make it one string
print(css) # print interacting color couples
###

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