Question

Consider the following four events and their vector timestamps: a: (3, 8, 4), b: (2, 2, 5), c: (2, 5, 8), d: (3, 7, 8). Which event/events happened before event d? Which event/events is/are concurrent with event d?

Answer 1

Consider two events X and Y to see if two events are concurrent do an element by element comparision of the their timestamps.
case a ) if each element of timestamp of X is less than or equal to the corresponding element in timestamp of Y then X happens before Y.
case b) if each element of timestamp of X is greater than or equal to the corresponding element in timestamp of Y then X happens after Y.
case c) if some element in timestamp of X are greater than and the rest of them are not then the events are concurrent.

a: (3, 8, 4)
b: (2, 2, 5)
c: (2, 5, 8)
d: (3, 7, 8)

compare each timestamps with d -
--> a and d - 3<=3 , 8>7 , 4<8
a and d are concurrent
--> b and d - 2<3 , 2<7 , 5<8
b happened before d
--> c and d - 2<3 , 5<7 , 8<=8
c happened before d