mirror of https://github.com/poanetwork/gecko.git
86 lines
2.5 KiB
Go
86 lines
2.5 KiB
Go
// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
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// See the file LICENSE for licensing terms.
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package poll
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import (
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"fmt"
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"github.com/ava-labs/gecko/ids"
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)
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type earlyTermNoTraversalFactory struct {
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alpha int
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}
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// NewEarlyTermNoTraversalFactory returns a factory that returns polls with
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// early termination, without doing DAG traversals
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func NewEarlyTermNoTraversalFactory(alpha int) Factory {
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return &earlyTermNoTraversalFactory{alpha: alpha}
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}
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func (f *earlyTermNoTraversalFactory) New(vdrs ids.ShortSet) Poll {
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return &earlyTermNoTraversalPoll{
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polled: vdrs,
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alpha: f.alpha,
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}
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}
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// earlyTermNoTraversalPoll finishes when any remaining validators can't change
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// the result of the poll. However, does not terminate tightly with this bound.
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// It terminates as quickly as it can without performing any DAG traversals.
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type earlyTermNoTraversalPoll struct {
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votes ids.UniqueBag
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polled ids.ShortSet
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alpha int
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}
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// Vote registers a response for this poll
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func (p *earlyTermNoTraversalPoll) Vote(vdr ids.ShortID, votes []ids.ID) {
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if !p.polled.Contains(vdr) {
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// if the validator wasn't polled or already responded to this poll, we
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// should just drop the vote
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return
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}
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// make sure that a validator can't respond multiple times
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p.polled.Remove(vdr)
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// track the votes the validator responded with
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p.votes.Add(uint(p.polled.Len()), votes...)
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}
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// Finished returns true when all validators have voted
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func (p *earlyTermNoTraversalPoll) Finished() bool {
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// If there are no outstanding queries, the poll is finished
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numPending := p.polled.Len()
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if numPending == 0 {
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return true
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}
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// If there are still enough pending responses to include another vertex,
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// then the poll must wait for more responses
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if numPending > p.alpha {
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return false
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}
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// Ignore any vertex that has already received alpha votes. To safely skip
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// DAG traversal, assume that all votes for vertices with less than alpha
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// votes will be applied to a single shared ancestor. In this case, the poll
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// can terminate early, iff there are not enough pending votes for this
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// ancestor to receive alpha votes.
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partialVotes := ids.BitSet(0)
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for _, vote := range p.votes.List() {
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if voters := p.votes.GetSet(vote); voters.Len() < p.alpha {
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partialVotes.Union(voters)
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}
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}
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return partialVotes.Len()+numPending < p.alpha
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}
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// Result returns the result of this poll
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func (p *earlyTermNoTraversalPoll) Result() ids.UniqueBag { return p.votes }
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func (p *earlyTermNoTraversalPoll) String() string {
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return fmt.Sprintf("waiting on %s", p.polled)
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}
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