Prevent 0 value for committeesPerSlot in shuffle function (#648)

beacon-chain/casper/sharding.go

@@ -22,9 +22,9 @@ func ShuffleValidatorsToCommittees(seed common.Hash, activeValidators []*pb.Vali
 
 // splitBySlotShard splits the validator list into evenly sized committees and assigns each
 // committee to a slot and a shard. If the validator set is large, multiple committees are assigned
-// to a single slot and shard. See getCommitteeParams for more details.
+// to a single slot and shard. See getCommitteesPerSlot for more details.
 func splitBySlotShard(shuffledValidators []uint32, crosslinkStartShard uint64) []*pb.ShardAndCommitteeArray {
-	committeesPerSlot := getCommitteeParams(len(shuffledValidators))
+	committeesPerSlot := getCommitteesPerSlot(len(shuffledValidators))
 
 	committeBySlotAndShard := []*pb.ShardAndCommitteeArray{}
 
@@ -51,16 +51,21 @@ func splitBySlotShard(shuffledValidators []uint32, crosslinkStartShard uint64) [
 	return committeBySlotAndShard
 }
 
-// getCommitteeParams calculates the parameters for ShuffleValidatorsToCommittees.
-// If numActiveValidators > CycleLength * MinCommitteeSize, committees are based off a max amount
-// from either numActiveValidators / CycleLength /  MinCommitteeSize or
-// it is decided from the ShardCount / CycleLength.
-func getCommitteeParams(numActiveValidators int) (committeesPerSlot int) {
+// getCommitteesPerSlot calculates the parameters for ShuffleValidatorsToCommittees.
+// The minimum value for committeesPerSlot is 1.
+// Otherwise, the value for committeesPerSlot is the smaller of
+// numActiveValidators / CycleLength /  (MinCommitteeSize*2) + 1 or
+// ShardCount / CycleLength.
+func getCommitteesPerSlot(numActiveValidators int) int {
 	cycleLength := int(params.GetConfig().CycleLength)
-	boundOnAVS := numActiveValidators/cycleLength/int(params.GetConfig().MinCommiteeSize*2) + 1
+	boundOnValidators := numActiveValidators/cycleLength/int(params.GetConfig().MinCommiteeSize*2) + 1
 	boundOnShardCount := params.GetConfig().ShardCount / cycleLength
-	if boundOnAVS > boundOnShardCount {
+
+	// Ensure that comitteesPerSlot is at least 1.
+	if boundOnShardCount == 0 {
+		return 1
+	} else if boundOnValidators > boundOnShardCount {
 		return boundOnShardCount
 	}
-	return boundOnAVS
+	return boundOnValidators
 }

beacon-chain/casper/sharding_test.go

@@ -99,33 +99,48 @@ func TestSmallSampleValidators(t *testing.T) {
 	}
 }
 
-func TestGetCommitteeParamsSmallValidatorSet(t *testing.T) {
+func TestGetCommitteesPerSlotSmallValidatorSet(t *testing.T) {
 	numValidators := int(params.GetConfig().CycleLength * params.GetConfig().MinCommiteeSize / 4)
 
-	committesPerSlot := getCommitteeParams(numValidators)
+	committesPerSlot := getCommitteesPerSlot(numValidators)
 	if committesPerSlot != 1 {
 		t.Fatalf("Expected committeesPerSlot to equal %d: got %d", 1, committesPerSlot)
 	}
 }
 
-func TestGetCommitteeParamsRegularValidatorSet(t *testing.T) {
+func TestGetCommitteesPerSlotRegularValidatorSet(t *testing.T) {
 	numValidators := int(params.GetConfig().CycleLength * params.GetConfig().MinCommiteeSize)
 
-	committesPerSlot := getCommitteeParams(numValidators)
+	committesPerSlot := getCommitteesPerSlot(numValidators)
 	if committesPerSlot != 1 {
 		t.Fatalf("Expected committeesPerSlot to equal %d: got %d", 1, committesPerSlot)
 	}
 }
 
-func TestGetCommitteeParamsLargeValidatorSet(t *testing.T) {
+func TestGetCommitteesPerSlotLargeValidatorSet(t *testing.T) {
 	numValidators := int(params.GetConfig().CycleLength*params.GetConfig().MinCommiteeSize) * 8
 
-	committesPerSlot := getCommitteeParams(numValidators)
+	committesPerSlot := getCommitteesPerSlot(numValidators)
 	if committesPerSlot != 5 {
 		t.Fatalf("Expected committeesPerSlot to equal %d: got %d", 5, committesPerSlot)
 	}
 }
 
+func TestGetCommitteesPerSlotSmallShardCount(t *testing.T) {
+	config := params.GetConfig()
+	oldShardCount := config.ShardCount
+	config.ShardCount = int(config.CycleLength) - 1
+
+	numValidators := int(params.GetConfig().CycleLength * params.GetConfig().MinCommiteeSize)
+
+	committesPerSlot := getCommitteesPerSlot(numValidators)
+	if committesPerSlot != 1 {
+		t.Fatalf("Expected committeesPerSlot to equal %d: got %d", 1, committesPerSlot)
+	}
+
+	config.ShardCount = oldShardCount
+}
+
 func TestValidatorsBySlotShardRegularValidatorSet(t *testing.T) {
 	validatorIndices := []uint32{}
 	numValidators := int(params.GetConfig().CycleLength * params.GetConfig().MinCommiteeSize)

beacon-chain/params/config.go

@@ -58,7 +58,7 @@ var demoConfig = &Config{
 	GenesisTime:               time.Now(),
 	ModuloBias:                16777216,
 	CycleLength:               uint64(5),
-	ShardCount:                3,
+	ShardCount:                5,
 	Gwei:                      1e9,
 	DepositSize:               32,
 	SlotDuration:              uint64(8),

beacon-chain/types/crystallized_state_test.go

@@ -323,17 +323,24 @@ func TestNewDynastyRecalculations(t *testing.T) {
 	}
 }
 
+func TestInitGenesisJsonFailure(t *testing.T) {
+	fname := "/genesis.json"
+	pwd, _ := os.Getwd()
+	fnamePath := pwd + fname
+
+	_, err := NewGenesisCrystallizedState(fnamePath)
+	if err == nil {
+		t.Fatalf("genesis.json should have failed %v", err)
+	}
+}
+
 func TestInitGenesisJson(t *testing.T) {
 	fname := "/genesis.json"
 	pwd, _ := os.Getwd()
 	fnamePath := pwd + fname
 	os.Remove(fnamePath)
 
-	_, err := NewGenesisCrystallizedState(fnamePath)
-	if err == nil {
-		t.Fatalf("genesis.json should have failed %v", err)
-	}
-
+	params.SetEnv("demo")
 	cStateJSON := &pb.CrystallizedState{
 		LastStateRecalculationSlot: 0,
 		JustifiedStreak:            1,

validator/beacon/service.go

@@ -111,7 +111,6 @@ func (s *Service) Stop() error {
 // From this, the validator client can deduce what slot interval the beacon
 // node is in and determine when exactly it is time to propose or attest.
 func (s *Service) fetchCurrentAssignmentsAndGenesisTime(client pb.BeaconServiceClient) {
-
 	// Currently fetches assignments for all validators.
 	req := &pb.ValidatorAssignmentRequest{
 		AllValidators: true,

validator/node/node.go

@@ -190,7 +190,6 @@ func (s *ShardEthereum) registerTXPool() error {
 // registerBeaconService registers a service that fetches streams from a beacon node
 // via RPC.
 func (s *ShardEthereum) registerBeaconService(pubKey []byte) error {
-
 	var rpcService *rpcclient.Service
 	if err := s.services.FetchService(&rpcService); err != nil {
 		return err