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Implement error driven snowflake hardcoded to support a single beta #2978

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merged 8 commits into from
Jun 6, 2024
Merged

Implement error driven snowflake hardcoded to support a single beta #2978

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5ae5fb9
Implement error driven snowflake hardcoded to a single confidence cou…
aaronbuchwald May 1, 2024
c38091f
clean up comments
aaronbuchwald May 1, 2024
f165b2a
Merge branch 'master' into flexible-snowflake-single-counter
aaronbuchwald Jun 3, 2024
1fd35ce
Move alphaConfidence/beta slices into a slice of structs
aaronbuchwald Jun 4, 2024
70306e7
Use slices.Clone instead of copy for cloning confidence slice
aaronbuchwald Jun 4, 2024
efe599e
Use slices.Clone in unary snowflake
aaronbuchwald Jun 4, 2024
6d29503
Call RecordSuccessfulPoll for every successful poll
aaronbuchwald Jun 5, 2024
abda297
Merge branch 'master' into flexible-snowflake-single-counter
StephenButtolph Jun 6, 2024
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67 changes: 42 additions & 25 deletions snow/consensus/snowball/binary_snowflake.go
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Original file line number Diff line number Diff line change
Expand Up @@ -11,29 +11,38 @@ func newBinarySnowflake(alphaPreference, alphaConfidence, beta, choice int) bina
return binarySnowflake{
binarySlush: newBinarySlush(choice),
alphaPreference: alphaPreference,
alphaConfidence: alphaConfidence,
beta: beta,
terminationConditions: []terminationCondition{
{
alphaConfidence: alphaConfidence,
beta: beta,
},
},
confidence: make([]int, 1),
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}
}

// binarySnowflake is the implementation of a binary snowflake instance
// Invariant:
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// len(terminationConditions) == len(confidence)
// terminationConditions[i].alphaConfidence < terminationConditions[i+1].alphaConfidence
// terminationConditions[i].beta <= terminationConditions[i+1].beta
// confidence[i] >= confidence[i+1] (except after finalizing due to early termination)
type binarySnowflake struct {
// wrap the binary slush logic
binarySlush

// confidence tracks the number of successful polls in a row that have
// returned the preference
confidence int

// alphaPreference is the threshold required to update the preference
alphaPreference int

// alphaConfidence is the threshold required to increment the confidence counter
alphaConfidence int
// terminationConditions gives the ascending ordered list of alphaConfidence values
// required to increment the corresponding confidence counter.
// The corresponding beta values give the threshold required to finalize this instance.
terminationConditions []terminationCondition

// beta is the number of consecutive successful queries required for
// finalization.
beta int
// confidence is the number of consecutive succcessful polls for a given
// alphaConfidence threshold.
// This instance finalizes when confidence[i] >= terminationConditions[i].beta for any i
confidence []int

// finalized prevents the state from changing after the required number of
// consecutive polls has been reached
Expand All @@ -50,26 +59,34 @@ func (sf *binarySnowflake) RecordPoll(count, choice int) {
return
}

if count < sf.alphaConfidence {
sf.confidence = 0
// If I need to change my preference, record the new preference
// and reset all my confidence counters.
if choice != sf.Preference() {
sf.binarySlush.RecordSuccessfulPoll(choice)
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Same comment as this other place... just feels odd only to call RecordSuccessfulPoll if it is for a different color...

return
clear(sf.confidence)
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}

if preference := sf.Preference(); preference == choice {
sf.confidence++
} else {
// confidence is set to 1 because there has already been 1 successful
// poll, namely this poll.
sf.confidence = 1
for i, terminationCondition := range sf.terminationConditions {
// If I did not reach this alpha threshold, I did not
// reach any more alpha thresholds.
// Clear the remaining confidence counters.
if count < terminationCondition.alphaConfidence {
clear(sf.confidence[i:])
return
}

// I reached this alpha threshold, increment the confidence counter
// and check if I can finalize.
sf.confidence[i]++
if sf.confidence[i] >= terminationCondition.beta {
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sf.finalized = true
return
}
}

sf.finalized = sf.confidence >= sf.beta
sf.binarySlush.RecordSuccessfulPoll(choice)
}

func (sf *binarySnowflake) RecordUnsuccessfulPoll() {
sf.confidence = 0
clear(sf.confidence)
}

func (sf *binarySnowflake) Finalized() bool {
Expand All @@ -78,7 +95,7 @@ func (sf *binarySnowflake) Finalized() bool {

func (sf *binarySnowflake) String() string {
return fmt.Sprintf("SF(Confidence = %d, Finalized = %v, %s)",
sf.confidence,
sf.confidence[0],
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sf.finalized,
&sf.binarySlush)
}
67 changes: 42 additions & 25 deletions snow/consensus/snowball/nnary_snowflake.go
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Expand Up @@ -15,30 +15,39 @@ func newNnarySnowflake(alphaPreference, alphaConfidence, beta int, choice ids.ID
return nnarySnowflake{
nnarySlush: newNnarySlush(choice),
alphaPreference: alphaPreference,
alphaConfidence: alphaConfidence,
beta: beta,
terminationConditions: []terminationCondition{
{
alphaConfidence: alphaConfidence,
beta: beta,
},
},
confidence: make([]int, 1),
}
}

// nnarySnowflake is the implementation of a snowflake instance with an
// unbounded number of choices
// Invariant:
// len(terminationConditions) == len(confidence)
// terminationConditions[i].alphaConfidence < terminationConditions[i+1].alphaConfidence
// terminationConditions[i].beta <= terminationConditions[i+1].beta
// confidence[i] >= confidence[i+1] (except after finalizing due to early termination)
type nnarySnowflake struct {
// wrap the n-nary slush logic
nnarySlush

// beta is the number of consecutive successful queries required for
// finalization.
beta int

// alphaPreference is the threshold required to update the preference
alphaPreference int

// alphaConfidence is the threshold required to increment the confidence counter
alphaConfidence int
// terminationConditions gives the ascending ordered list of alphaConfidence values
// required to increment the corresponding confidence counter.
// The corresponding beta values give the threshold required to finalize this instance.
terminationConditions []terminationCondition

// confidence tracks the number of successful polls in a row that have
// returned the preference
confidence int
// confidence is the number of consecutive succcessful polls for a given
// alphaConfidence threshold.
// This instance finalizes when confidence[i] >= terminationConditions[i].beta for any i
confidence []int

// finalized prevents the state from changing after the required number of
// consecutive polls has been reached
Expand All @@ -57,26 +66,34 @@ func (sf *nnarySnowflake) RecordPoll(count int, choice ids.ID) {
return
}

if count < sf.alphaConfidence {
sf.confidence = 0
// If I need to change my preference, record the new preference
// and reset all my confidence counters.
if choice != sf.Preference() {
clear(sf.confidence)
sf.nnarySlush.RecordSuccessfulPoll(choice)
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I know this doesn't matter (and tbh might be an efficiency improvement) but it feels weird not to call nnarySlush. RecordSuccessfulPoll in every case here... Might just be me though

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I don't feel strongly about this. I can't imagine it's a meaningful performance improvement, so will go ahead and update it in both places.

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Addressed and updated the corresponding comment in both places

return
}

if preference := sf.Preference(); preference == choice {
sf.confidence++
} else {
// confidence is set to 1 because there has already been 1 successful
// poll, namely this poll.
sf.confidence = 1
for i, terminationCondition := range sf.terminationConditions {
// If I did not reach this alpha threshold, I did not
// reach any more alpha thresholds.
// Clear the remaining confidence counters.
if count < terminationCondition.alphaConfidence {
clear(sf.confidence[i:])
return
}

// I reached this alpha threshold, increment the confidence counter
// and check if I can finalize.
sf.confidence[i]++
if sf.confidence[i] >= terminationCondition.beta {
sf.finalized = true
return
}
}

sf.finalized = sf.confidence >= sf.beta
sf.nnarySlush.RecordSuccessfulPoll(choice)
}

func (sf *nnarySnowflake) RecordUnsuccessfulPoll() {
sf.confidence = 0
clear(sf.confidence)
}

func (sf *nnarySnowflake) Finalized() bool {
Expand All @@ -85,7 +102,7 @@ func (sf *nnarySnowflake) Finalized() bool {

func (sf *nnarySnowflake) String() string {
return fmt.Sprintf("SF(Confidence = %d, Finalized = %v, %s)",
sf.confidence,
sf.confidence[0],
sf.finalized,
&sf.nnarySlush)
}
5 changes: 5 additions & 0 deletions snow/consensus/snowball/parameters.go
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Expand Up @@ -122,3 +122,8 @@ func (p Parameters) MinPercentConnectedHealthy() float64 {
alphaRatio := float64(p.AlphaConfidence) / float64(p.K)
return alphaRatio*(1-MinPercentConnectedBuffer) + MinPercentConnectedBuffer
}

type terminationCondition struct {
alphaConfidence int
beta int
}
16 changes: 10 additions & 6 deletions snow/consensus/snowball/unary_snowball.go
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Expand Up @@ -30,14 +30,15 @@ func (sb *unarySnowball) RecordPoll(count int) {
}

func (sb *unarySnowball) Extend(choice int) Binary {
confidence := make([]int, len(sb.confidence))
copy(confidence, sb.confidence)
bs := &binarySnowball{
binarySnowflake: binarySnowflake{
binarySlush: binarySlush{preference: choice},
confidence: sb.confidence,
alphaPreference: sb.alphaPreference,
alphaConfidence: sb.alphaConfidence,
beta: sb.beta,
finalized: sb.Finalized(),
binarySlush: binarySlush{preference: choice},
confidence: confidence,
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alphaPreference: sb.alphaPreference,
terminationConditions: sb.terminationConditions,
finalized: sb.Finalized(),
},
preference: choice,
}
Expand All @@ -47,6 +48,9 @@ func (sb *unarySnowball) Extend(choice int) Binary {

func (sb *unarySnowball) Clone() Unary {
newSnowball := *sb
// Copy the confidence slice
newSnowball.confidence = make([]int, len(sb.confidence))
copy(newSnowball.confidence, sb.confidence)
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return &newSnowball
}

Expand Down
14 changes: 7 additions & 7 deletions snow/consensus/snowball/unary_snowball_test.go
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Expand Up @@ -9,7 +9,7 @@ import (
"github.com/stretchr/testify/require"
)

func UnarySnowballStateTest(t *testing.T, sb *unarySnowball, expectedPreferenceStrength, expectedConfidence int, expectedFinalized bool) {
func UnarySnowballStateTest(t *testing.T, sb *unarySnowball, expectedPreferenceStrength int, expectedConfidence []int, expectedFinalized bool) {
require := require.New(t)

require.Equal(expectedPreferenceStrength, sb.preferenceStrength)
Expand All @@ -26,25 +26,25 @@ func TestUnarySnowball(t *testing.T) {
sb := newUnarySnowball(alphaPreference, alphaConfidence, beta)

sb.RecordPoll(alphaConfidence)
UnarySnowballStateTest(t, &sb, 1, 1, false)
UnarySnowballStateTest(t, &sb, 1, []int{1}, false)

sb.RecordPoll(alphaPreference)
UnarySnowballStateTest(t, &sb, 2, 0, false)
UnarySnowballStateTest(t, &sb, 2, []int{0}, false)

sb.RecordPoll(alphaConfidence)
UnarySnowballStateTest(t, &sb, 3, 1, false)
UnarySnowballStateTest(t, &sb, 3, []int{1}, false)

sb.RecordUnsuccessfulPoll()
UnarySnowballStateTest(t, &sb, 3, 0, false)
UnarySnowballStateTest(t, &sb, 3, []int{0}, false)

sb.RecordPoll(alphaConfidence)
UnarySnowballStateTest(t, &sb, 4, 1, false)
UnarySnowballStateTest(t, &sb, 4, []int{1}, false)

sbCloneIntf := sb.Clone()
require.IsType(&unarySnowball{}, sbCloneIntf)
sbClone := sbCloneIntf.(*unarySnowball)

UnarySnowballStateTest(t, sbClone, 4, 1, false)
UnarySnowballStateTest(t, sbClone, 4, []int{1}, false)

binarySnowball := sbClone.Extend(0)

Expand Down
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