smegmesh/pkg/conn/cluster.go

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package conn
import (
"errors"
"math"
"math/rand"
"slices"
)
// ConnCluster splits nodes into clusters where nodes in a cluster communicate
// frequently and nodes outside of a cluster communicate infrequently
type ConnCluster interface {
GetNeighbours(global []string, selfId string) []string
GetInterCluster(global []string, selfId string) string
}
type ConnClusterImpl struct {
clusterSize int
}
func binarySearch(global []string, selfId string, groupSize int) (int, int) {
slices.Sort(global)
lower := 0
higher := len(global) - 1
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mid := (lower + higher) / 2
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for (higher+1)-lower > groupSize {
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if global[mid] < selfId {
lower = mid + 1
} else if global[mid] > selfId {
higher = mid - 1
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} else {
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break
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}
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mid = (lower + higher) / 2
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}
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return lower, int(math.Min(float64(lower+groupSize), float64(len(global))))
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}
// GetNeighbours return the neighbours 'nearest' to you. In this implementation the
// neighbours aren't actually the ones nearest to you but just the ones nearest
// to you alphabetically. Perform binary search to get the total group
func (i *ConnClusterImpl) GetNeighbours(global []string, selfId string) []string {
slices.Sort(global)
lower, higher := binarySearch(global, selfId, i.clusterSize)
// slice the list to get the neighbours
return global[lower:higher]
}
// GetInterCluster get nodes not in your cluster. Every round there is a given chance
// you will communicate with a random node that is not in your cluster.
func (i *ConnClusterImpl) GetInterCluster(global []string, selfId string) string {
// Doesn't matter if not in it. Get index of where the node 'should' be
slices.Sort(global)
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index, _ := binarySearch(global, selfId, 1)
randomCluster := rand.Intn(2) + 1
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// cluster is considered a heap
neighbourIndex := (2*index + (randomCluster * i.clusterSize)) % len(global)
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return global[neighbourIndex]
}
func NewConnCluster(clusterSize int) (ConnCluster, error) {
log2Cluster := math.Log2(float64(clusterSize))
if float64((log2Cluster))-log2Cluster != 0 {
return nil, errors.New("cluster must be a power of 2")
}
return &ConnClusterImpl{clusterSize: clusterSize}, nil
}