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binary_snowball.go
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binary_snowball.go
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// Copyright (C) 2019-2022, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package snowball
import (
"fmt"
)
var _ BinarySnowball = (*binarySnowball)(nil)
// binarySnowball is the implementation of a binary snowball instance
type binarySnowball struct {
// wrap the binary snowflake logic
binarySnowflake
// preference is the choice with the largest number of successful polls.
// Ties are broken by switching choice lazily
preference int
// numSuccessfulPolls tracks the total number of successful network polls of
// the 0 and 1 choices
numSuccessfulPolls [2]int
}
func (sb *binarySnowball) Initialize(beta, choice int) {
sb.binarySnowflake.Initialize(beta, choice)
sb.preference = choice
}
func (sb *binarySnowball) Preference() int {
// It is possible, with low probability, that the snowflake preference is
// not equal to the snowball preference when snowflake finalizes. However,
// this case is handled for completion. Therefore, if snowflake is
// finalized, then our finalized snowflake choice should be preferred.
if sb.Finalized() {
return sb.binarySnowflake.Preference()
}
return sb.preference
}
func (sb *binarySnowball) RecordSuccessfulPoll(choice int) {
sb.numSuccessfulPolls[choice]++
if sb.numSuccessfulPolls[choice] > sb.numSuccessfulPolls[1-choice] {
sb.preference = choice
}
sb.binarySnowflake.RecordSuccessfulPoll(choice)
}
func (sb *binarySnowball) String() string {
return fmt.Sprintf(
"SB(Preference = %d, NumSuccessfulPolls[0] = %d, NumSuccessfulPolls[1] = %d, %s)",
sb.preference,
sb.numSuccessfulPolls[0],
sb.numSuccessfulPolls[1],
&sb.binarySnowflake)
}