Move Get Cutoff Algo to Utils Package (#370)

beacon-chain/blockchain/core.go

@@ -270,52 +270,6 @@ func (b *BeaconChain) getAttestersProposer(seed common.Hash) ([]int, int, error)
 	return indices[:int(attesterCount)], indices[len(indices)-1], nil
 }
 
-// GetCutoffs is used to split up validators into groups at the start
-// of every epoch. It determines at what height validators can make
-// attestations and crosslinks. It returns lists of cutoff indices.
-func GetCutoffs(validatorCount int) []int {
-	var heightCutoff = []int{0}
-	var heights []int
-	var heightCount float64
-
-	// Skip heights if there's not enough validators to fill in a min sized committee.
-	if validatorCount < params.EpochLength*params.MinCommiteeSize {
-		heightCount = math.Floor(float64(validatorCount) / params.MinCommiteeSize)
-		for i := 0; i < int(heightCount); i++ {
-			heights = append(heights, (i*params.Cofactor)%params.EpochLength)
-		}
-		// Enough validators, fill in all the heights.
-	} else {
-		heightCount = params.EpochLength
-		for i := 0; i < int(heightCount); i++ {
-			heights = append(heights, i)
-		}
-	}
-
-	filled := 0
-	appendHeight := false
-	for i := 0; i < params.EpochLength-1; i++ {
-		appendHeight = false
-		for _, height := range heights {
-			if i == height {
-				appendHeight = true
-			}
-		}
-		if appendHeight {
-			filled++
-			heightCutoff = append(heightCutoff, filled*validatorCount/int(heightCount))
-		} else {
-			heightCutoff = append(heightCutoff, heightCutoff[len(heightCutoff)-1])
-		}
-	}
-	heightCutoff = append(heightCutoff, validatorCount)
-
-	// TODO: For the validators assigned to each height, split them up into
-	// committees for different shards. Do not assign the last END_EPOCH_GRACE_PERIOD
-	// heights in a epoch to any shards.
-	return heightCutoff
-}
-
 // calculateRewardsFFG adjusts validators balances by applying rewards or penalties
 // based on FFG incentive structure.
 func (b *BeaconChain) calculateRewardsFFG() error {

beacon-chain/blockchain/core_test.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"context"
 	"errors"
-	"math"
 	"reflect"
 	"testing"
 
@@ -419,49 +418,6 @@ func TestRotateValidatorSet(t *testing.T) {
 	}
 }
 
-func TestCutOffValidatorSet(t *testing.T) {
-	// Test scenario #1: Assume there's enough validators to fill in all the heights.
-	validatorCount := params.EpochLength * params.MinCommiteeSize
-	cutoffsValidators := GetCutoffs(validatorCount)
-
-	// The length of cutoff list should be 65. Since there is 64 heights per epoch,
-	// it means during every height, a new set of 128 validators will form a committee.
-	expectedCount := int(math.Ceil(float64(validatorCount)/params.MinCommiteeSize)) + 1
-	if len(cutoffsValidators) != expectedCount {
-		t.Errorf("Incorrect count for cutoffs validator. Wanted: %v, Got: %v", expectedCount, len(cutoffsValidators))
-	}
-
-	// Verify each cutoff is an increment of MinCommiteeSize, it means 128 validators forms a
-	// a committee and get to attest per height.
-	count := 0
-	for _, cutoff := range cutoffsValidators {
-		if cutoff != count {
-			t.Errorf("cutoffsValidators did not get 128 increment. Wanted: count, Got: %v", cutoff)
-		}
-		count += params.MinCommiteeSize
-	}
-
-	// Test scenario #2: Assume there's not enough validators to fill in all the heights.
-	validatorCount = 1000
-	cutoffsValidators = unique(GetCutoffs(validatorCount))
-	// With 1000 validators, we can't attest every height. Given min committee size is 128,
-	// we can only attest 7 heights. round down 1000 / 128 equals to 7, means the length is 8.
-	expectedCount = int(math.Ceil(float64(validatorCount) / params.MinCommiteeSize))
-	if len(unique(cutoffsValidators)) != expectedCount {
-		t.Errorf("Incorrect count for cutoffs validator. Wanted: %v, Got: %v", expectedCount, validatorCount/params.MinCommiteeSize)
-	}
-
-	// Verify each cutoff is an increment of 142~143 (1000 / 7).
-	count = 0
-	for _, cutoff := range cutoffsValidators {
-		num := count * validatorCount / (len(cutoffsValidators) - 1)
-		if cutoff != num {
-			t.Errorf("cutoffsValidators did not get correct increment. Wanted: %v, Got: %v", num, cutoff)
-		}
-		count++
-	}
-}
-
 func TestIsEpochTransition(t *testing.T) {
 	beaconChain, db := startInMemoryBeaconChain(t)
 	defer db.Close()
@@ -658,19 +614,6 @@ func TestComputeValidatorRewardsAndPenalties(t *testing.T) {
 	}
 }
 
-// helper function to remove duplicates in a int slice.
-func unique(ints []int) []int {
-	keys := make(map[int]bool)
-	list := []int{}
-	for _, int := range ints {
-		if _, value := keys[int]; !value {
-			keys[int] = true
-			list = append(list, int)
-		}
-	}
-	return list
-}
-
 // NewBlock is a helper method to create blocks with valid defaults.
 // For a generic block, use NewBlock(t, nil)
 func NewBlock(t *testing.T, b *pb.BeaconBlockResponse) *types.Block {

beacon-chain/utils/shuffle.go

@@ -2,6 +2,7 @@ package utils
 
 import (
 	"errors"
+	"math"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/prysmaticlabs/prysm/beacon-chain/params"
@@ -35,3 +36,49 @@ func ShuffleIndices(seed common.Hash, validatorCount int) ([]int, error) {
 	}
 	return validatorList, nil
 }
+
+// GetCutoffs is used to split up validators into groups at the start
+// of every epoch. It determines at what height validators can make
+// attestations and crosslinks. It returns lists of cutoff indices.
+func GetCutoffs(validatorCount int) []int {
+	var heightCutoff = []int{0}
+	var heights []int
+	var heightCount float64
+
+	// Skip heights if there's not enough validators to fill in a min sized committee.
+	if validatorCount < params.EpochLength*params.MinCommiteeSize {
+		heightCount = math.Floor(float64(validatorCount) / params.MinCommiteeSize)
+		for i := 0; i < int(heightCount); i++ {
+			heights = append(heights, (i*params.Cofactor)%params.EpochLength)
+		}
+		// Enough validators, fill in all the heights.
+	} else {
+		heightCount = params.EpochLength
+		for i := 0; i < int(heightCount); i++ {
+			heights = append(heights, i)
+		}
+	}
+
+	filled := 0
+	appendHeight := false
+	for i := 0; i < params.EpochLength-1; i++ {
+		appendHeight = false
+		for _, height := range heights {
+			if i == height {
+				appendHeight = true
+			}
+		}
+		if appendHeight {
+			filled++
+			heightCutoff = append(heightCutoff, filled*validatorCount/int(heightCount))
+		} else {
+			heightCutoff = append(heightCutoff, heightCutoff[len(heightCutoff)-1])
+		}
+	}
+	heightCutoff = append(heightCutoff, validatorCount)
+
+	// TODO: For the validators assigned to each height, split them up into
+	// committees for different shards. Do not assign the last END_EPOCH_GRACE_PERIOD
+	// heights in a epoch to any shards.
+	return heightCutoff
+}

beacon-chain/utils/shuffle_test.go

@@ -1,6 +1,7 @@
 package utils
 
 import (
+	"math"
 	"reflect"
 	"testing"
 
@@ -31,3 +32,60 @@ func TestShuffleIndices(t *testing.T) {
 		t.Errorf("2 shuffled lists shouldn't be equal")
 	}
 }
+
+func TestCutOffValidatorSet(t *testing.T) {
+	// Test scenario #1: Assume there's enough validators to fill in all the heights.
+	validatorCount := params.EpochLength * params.MinCommiteeSize
+	cutoffsValidators := GetCutoffs(validatorCount)
+
+	// The length of cutoff list should be 65. Since there is 64 heights per epoch,
+	// it means during every height, a new set of 128 validators will form a committee.
+	expectedCount := int(math.Ceil(float64(validatorCount)/params.MinCommiteeSize)) + 1
+	if len(cutoffsValidators) != expectedCount {
+		t.Errorf("Incorrect count for cutoffs validator. Wanted: %v, Got: %v", expectedCount, len(cutoffsValidators))
+	}
+
+	// Verify each cutoff is an increment of MinCommiteeSize, it means 128 validators forms a
+	// a committee and get to attest per height.
+	count := 0
+	for _, cutoff := range cutoffsValidators {
+		if cutoff != count {
+			t.Errorf("cutoffsValidators did not get 128 increment. Wanted: count, Got: %v", cutoff)
+		}
+		count += params.MinCommiteeSize
+	}
+
+	// Test scenario #2: Assume there's not enough validators to fill in all the heights.
+	validatorCount = 1000
+	cutoffsValidators = unique(GetCutoffs(validatorCount))
+	// With 1000 validators, we can't attest every height. Given min committee size is 128,
+	// we can only attest 7 heights. round down 1000 / 128 equals to 7, means the length is 8.
+	expectedCount = int(math.Ceil(float64(validatorCount) / params.MinCommiteeSize))
+	if len(unique(cutoffsValidators)) != expectedCount {
+		t.Errorf("Incorrect count for cutoffs validator. Wanted: %v, Got: %v", expectedCount, validatorCount/params.MinCommiteeSize)
+	}
+
+	// Verify each cutoff is an increment of 142~143 (1000 / 7).
+	count = 0
+	for _, cutoff := range cutoffsValidators {
+		num := count * validatorCount / (len(cutoffsValidators) - 1)
+		if cutoff != num {
+			t.Errorf("cutoffsValidators did not get correct increment. Wanted: %v, Got: %v", num, cutoff)
+		}
+		count++
+	}
+}
+
+// helper function to remove duplicates in a int slice.
+func unique(ints []int) []int {
+	keys := make(map[int]bool)
+	list := []int{}
+	for _, int := range ints {
+		if _, value := keys[int]; !value {
+			keys[int] = true
+			list = append(list, int)
+		}
+	}
+	return list
+
+}