
Logical Clocks Are Easy (2016) - bladecatcher
https://queue.acm.org/detail.cfm?id=2917756
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perl4ever
"Time, however, totally orders all events, even those unrelated"

Really? Given how fast computers are, and the global nature of the Internet, I
thought it is easily possible for them to be separated by more distance than
light can travel in a relevant amount of time.

"there is no unique ordering of spacelike events--events that happen in order
1 > 2 > 3 in frame A may happen in order 2 > 1 > 3 in frame B. In fact, for
any two spacelike separated events, it is possible to find a reference frame
where you can reverse the order in which they happen."

[https://physics.stackexchange.com/questions/75763/can-
specia...](https://physics.stackexchange.com/questions/75763/can-special-
relativity-distort-the-relative-order-in-which-events-occur)

~~~
lou1306
A fair objection. Indeed, in the cited paper ( _Time, clocks, and the ordering
of events in a distributed system_ ) Lamport explicitly assumes a Newtonian
spacetime.

~~~
Filligree
Which is fine, so long as the computers aren't moving at relativistic speeds
relative to each other. Newtonian spacetime is an accurate approximation.

~~~
jerf
Even if they were, I would expect the adjustments to not be that difficult.
This sort of temporal logic already accepts and encompasses many of the issues
relativistic time would raise. For instance, computer science already has to
handle the possibility that event X will occur but remote site Y literally
_never_ hears about it, or hears about it many, many, _many_ multiples of the
fundamental speed-of-light latency later, arbitrarily interleaved with any
number of other events in the mean time. It would be less of a shock to
computer science than it was to physics.

~~~
gizmo686
The relevant result from relativity is that you cannot rely on synchronized
clocks to construct an unambiguous ordering of events. Latency by itself is
not sufficient to cause this, as the system could still wait until the message
has been fully distributed, then use the timestamps to reconstruct the
timeline.

However, CS does have to deal with this issue for the simple reason that we
are already unable to synchronized our clocks to the extent necessary to avoid
it (or, at least, it is not worth the engineering effort to do so).

------
jamesblonde
We are from a distributed systems research group.

We called our company Logical Clocks - couldn't believe i could get the .com
domain name only 2 years ago....

