Message Ordering
Mattern Vector Clocks
Each processor keeps a local counter
And a vector with values for each other processor
Upon sending, the vector is added to messages
At reception, the local vector gets the maximum
(component by component)
if a happened before b is equivalent
to vector(a) less or equal than vector(b)
if a is concurrent to b is equivalent
to vector(a) is not comparable to vector(b)
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