estimate safety  

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jerry
(@jerry)
Eminent Member
Joined:7 months  ago
Posts: 31
04/06/2018 4:18 am  

For a node's local states changes in the way below

σ -> σ' -> σ'' -> σ'''

And estimator is a function in binary consensus outpus 0 or 1.

estimator(σ) ∈ {0, 1}

An estimate in the binary consensus (0 or 1) is said to be "safe" for a particular protocol state if it is returned by the estimator on all future protocol states.

I am trying to understand this line. "the estimator on all future protocol states"

Does it imply the function estimator output same result for all future states?

estimator(σ) = estimator(σ') = estimator(σ'')

Or does it imply  the function estimator might change when state changes, but their output on same state remain the same?

estimator1(σ) = estimator2(σ) = estimator2(σ)

 


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MichaelBirch
(@michaelbirch)
Member Moderator
Joined:8 months  ago
Posts: 41
06/06/2018 1:25 pm  

The estimator is a fixed function which is part of the protocol, it never changes. The meaning is that the output of the estimator will be the same for every protocol state that the node might transition to. The binary consensus is a little simplistic in this respect because there are only two options. In general safety means that the output of the estimator in all future states will be consistent with the current output. For example, in the blockchain case a block being safe means that it will be in the "longest chain" forever.


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