diff --git a/base/copier/copier.go b/common/copier/copier.go
similarity index 99%
rename from base/copier/copier.go
rename to common/copier/copier.go
index 621af599e..fd8b2c4c2 100644
--- a/base/copier/copier.go
+++ b/common/copier/copier.go
@@ -16,8 +16,9 @@ package copier
 
 import (
 	"encoding"
-	"github.com/juju/errors"
 	"reflect"
+
+	"github.com/juju/errors"
 )
 
 func Copy(dst, src interface{}) error {
diff --git a/base/copier/copier_test.go b/common/copier/copier_test.go
similarity index 99%
rename from base/copier/copier_test.go
rename to common/copier/copier_test.go
index fca089e67..eee876b90 100644
--- a/base/copier/copier_test.go
+++ b/common/copier/copier_test.go
@@ -15,10 +15,11 @@
 package copier
 
 import (
+	"testing"
+
 	"github.com/juju/errors"
 	"github.com/stretchr/testify/assert"
 	"google.golang.org/protobuf/proto"
-	"testing"
 )
 
 func TestPrimitives(t *testing.T) {
diff --git a/base/jsonutil/json.go b/common/jsonutil/json.go
similarity index 100%
rename from base/jsonutil/json.go
rename to common/jsonutil/json.go
diff --git a/base/jsonutil/json_test.go b/common/jsonutil/json_test.go
similarity index 99%
rename from base/jsonutil/json_test.go
rename to common/jsonutil/json_test.go
index 7e7610542..b82f4de6d 100644
--- a/base/jsonutil/json_test.go
+++ b/common/jsonutil/json_test.go
@@ -15,8 +15,9 @@
 package jsonutil
 
 import (
-	"github.com/stretchr/testify/assert"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 func TestUnmarshal(t *testing.T) {
diff --git a/common/parallel/parallel.go b/common/parallel/parallel.go
index 071244784..07c35bf84 100644
--- a/common/parallel/parallel.go
+++ b/common/parallel/parallel.go
@@ -17,7 +17,7 @@ package parallel
 import (
 	"sync"
 
-	"github.com/gorse-io/gorse/base"
+	"github.com/gorse-io/gorse/common/util"
 	"github.com/juju/errors"
 	"github.com/samber/lo"
 	"modernc.org/mathutil"
@@ -56,7 +56,7 @@ func Parallel(nJobs, nWorkers int, worker func(workerId, jobId int) error) error
 			// start workers
 			workerId := j
 			wg.Go(func() {
-				defer base.CheckPanic()
+				defer util.CheckPanic()
 				for {
 					// read job
 					jobId, ok := <-c
diff --git a/common/parallel/parallel_test.go b/common/parallel/parallel_test.go
index 4562aab68..5cc90b41e 100644
--- a/common/parallel/parallel_test.go
+++ b/common/parallel/parallel_test.go
@@ -20,13 +20,13 @@ import (
 	"time"
 
 	mapset "github.com/deckarep/golang-set/v2"
-	"github.com/gorse-io/gorse/base"
+	"github.com/gorse-io/gorse/common/util"
 	"github.com/stretchr/testify/assert"
 )
 
 func TestParallel(t *testing.T) {
 	synctest.Test(t, func(t *testing.T) {
-		a := base.RangeInt(10000)
+		a := util.RangeInt(10000)
 		b := make([]int, len(a))
 		workerIds := make([]int, len(a))
 		// multiple threads
@@ -55,7 +55,7 @@ func TestParallel(t *testing.T) {
 func TestFor(t *testing.T) {
 	synctest.Test(t, func(t *testing.T) {
 		// multiple threads
-		a := base.RangeInt(10000)
+		a := util.RangeInt(10000)
 		b := make([]int, len(a))
 		For(len(a), 4, func(jobId int) {
 			b[jobId] = a[jobId]
@@ -73,7 +73,7 @@ func TestFor(t *testing.T) {
 
 func TestForEach(t *testing.T) {
 	synctest.Test(t, func(t *testing.T) {
-		a := base.RangeInt(10000)
+		a := util.RangeInt(10000)
 		b := make([]int, len(a))
 		// multiple threads
 		ForEach(a, 4, func(i, v int) {
@@ -94,7 +94,7 @@ func TestForEach(t *testing.T) {
 
 func TestBatchParallel(t *testing.T) {
 	synctest.Test(t, func(t *testing.T) {
-		a := base.RangeInt(10000)
+		a := util.RangeInt(10000)
 		b := make([]int, len(a))
 		workerIds := make([]int, len(a))
 		// multiple threads
diff --git a/base/random.go b/common/util/random.go
similarity index 99%
rename from base/random.go
rename to common/util/random.go
index 72a9a7b7c..758581fe0 100644
--- a/base/random.go
+++ b/common/util/random.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package base
+package util
 
 import (
 	"math/rand"
diff --git a/base/random_test.go b/common/util/random_test.go
similarity index 99%
rename from base/random_test.go
rename to common/util/random_test.go
index 364c6dcc3..4b26730a6 100644
--- a/base/random_test.go
+++ b/common/util/random_test.go
@@ -11,7 +11,7 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-package base
+package util
 
 import (
 	"testing"
diff --git a/base/util.go b/common/util/util.go
similarity index 99%
rename from base/util.go
rename to common/util/util.go
index bc2176f5d..a41169bdd 100644
--- a/base/util.go
+++ b/common/util/util.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package base
+package util
 
 import (
 	"fmt"
diff --git a/base/util_test.go b/common/util/util_test.go
similarity index 99%
rename from base/util_test.go
rename to common/util/util_test.go
index 095334123..f189a3e25 100644
--- a/base/util_test.go
+++ b/common/util/util_test.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package base
+package util
 
 import (
 	"testing"
diff --git a/dataset/dataset.go b/dataset/dataset.go
index cc56367f2..ddbf43898 100644
--- a/dataset/dataset.go
+++ b/dataset/dataset.go
@@ -24,7 +24,6 @@ import (
 
 	"github.com/chewxy/math32"
 	mapset "github.com/deckarep/golang-set/v2"
-	"github.com/gorse-io/gorse/base"
 	"github.com/gorse-io/gorse/common/util"
 	"github.com/gorse-io/gorse/model"
 	"github.com/gorse-io/gorse/storage/data"
@@ -65,7 +64,7 @@ type CTRSplit interface {
 	CountContextLabels() int
 	CountPositive() int
 	CountNegative() int
-	GetIndex() base.UnifiedIndex
+	GetIndex() UnifiedIndex
 	GetTarget(i int) float32
 	Get(i int) ([]int32, []float32, float32)
 }
@@ -230,7 +229,7 @@ func (d *Dataset) AddFeedback(userId, itemId string) {
 
 func (d *Dataset) SampleUserNegatives(excludeSet CFSplit, numCandidates int) [][]int32 {
 	if len(d.negatives) == 0 {
-		rng := base.NewRandomGenerator(0)
+		rng := util.NewRandomGenerator(0)
 		d.negatives = make([][]int32, d.CountUsers())
 		for userIndex := 0; userIndex < d.CountUsers(); userIndex++ {
 			s1 := mapset.NewSet(d.GetUserFeedback()[userIndex]...)
@@ -252,7 +251,7 @@ func (d *Dataset) SplitCF(numTestUsers int, seed int64) (CFSplit, CFSplit) {
 	trainSet.itemFeedback, testSet.itemFeedback = make([][]int32, d.CountItems()), make([][]int32, d.CountItems())
 	trainSet.userDict, testSet.userDict = d.userDict, d.userDict
 	trainSet.itemDict, testSet.itemDict = d.itemDict, d.itemDict
-	rng := base.NewRandomGenerator(seed)
+	rng := util.NewRandomGenerator(seed)
 	if numTestUsers >= d.CountUsers() || numTestUsers <= 0 {
 		for userIndex := int32(0); userIndex < int32(d.CountUsers()); userIndex++ {
 			if len(d.userFeedback[userIndex]) > 0 {
diff --git a/dataset/dict.go b/dataset/dict.go
index 5b2356f72..5fe2ad1a9 100644
--- a/dataset/dict.go
+++ b/dataset/dict.go
@@ -14,8 +14,6 @@
 
 package dataset
 
-import "github.com/gorse-io/gorse/base"
-
 type FreqDict struct {
 	si  map[string]int32
 	is  []string
@@ -77,8 +75,8 @@ func (d *FreqDict) Freq(id int32) int32 {
 	return d.cnt[id]
 }
 
-func (d *FreqDict) ToIndex() *base.Index {
-	return &base.Index{
+func (d *FreqDict) ToIndex() *Index {
+	return &Index{
 		Numbers: d.si,
 		Names:   d.is,
 	}
diff --git a/base/index.go b/dataset/index.go
similarity index 99%
rename from base/index.go
rename to dataset/index.go
index bdfcc0704..e320c2b98 100644
--- a/base/index.go
+++ b/dataset/index.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package base
+package dataset
 
 import (
 	"encoding/binary"
diff --git a/base/index_test.go b/dataset/index_test.go
similarity index 98%
rename from base/index_test.go
rename to dataset/index_test.go
index 40db7bfda..42a427e23 100644
--- a/base/index_test.go
+++ b/dataset/index_test.go
@@ -1,4 +1,4 @@
-package base
+package dataset
 
 import (
 	"bytes"
diff --git a/base/unified_index.go b/dataset/unified_index.go
similarity index 99%
rename from base/unified_index.go
rename to dataset/unified_index.go
index c4f6163fc..0153466eb 100644
--- a/base/unified_index.go
+++ b/dataset/unified_index.go
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package base
+package dataset
 
 import (
 	"encoding/binary"
diff --git a/base/unified_index_test.go b/dataset/unified_index_test.go
similarity index 99%
rename from base/unified_index_test.go
rename to dataset/unified_index_test.go
index b595caa5b..9a260842a 100644
--- a/base/unified_index_test.go
+++ b/dataset/unified_index_test.go
@@ -11,7 +11,7 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-package base
+package dataset
 
 import (
 	"bytes"
diff --git a/master/master.go b/master/master.go
index 6b34b9a5d..76d6e5969 100644
--- a/master/master.go
+++ b/master/master.go
@@ -26,7 +26,6 @@ import (
 
 	"github.com/coreos/go-oidc/v3/oidc"
 	"github.com/emicklei/go-restful/v3"
-	"github.com/gorse-io/gorse/base"
 	"github.com/gorse-io/gorse/common/log"
 	"github.com/gorse-io/gorse/common/monitor"
 	"github.com/gorse-io/gorse/common/parallel"
@@ -305,7 +304,7 @@ func (m *Master) Shutdown() {
 }
 
 func (m *Master) RunTasksLoop() {
-	defer base.CheckPanic()
+	defer util.CheckPanic()
 	var (
 		err error
 		//firstLoop = true
diff --git a/master/rest.go b/master/rest.go
index ddde771a0..6927328cc 100644
--- a/master/rest.go
+++ b/master/rest.go
@@ -34,7 +34,6 @@ import (
 	"github.com/go-viper/mapstructure/v2"
 	"github.com/gorilla/securecookie"
 	_ "github.com/gorse-io/dashboard"
-	"github.com/gorse-io/gorse/base"
 	"github.com/gorse-io/gorse/cmd/version"
 	"github.com/gorse-io/gorse/common/expression"
 	"github.com/gorse-io/gorse/common/log"
@@ -1039,7 +1038,7 @@ func (m *Master) importExportUsers(response http.ResponseWriter, request *http.R
 				return
 			}
 			// validate user id
-			if err = base.ValidateId(user.UserId); err != nil {
+			if err = util.ValidateId(user.UserId); err != nil {
 				server.BadRequest(restful.NewResponse(response),
 					fmt.Errorf("invalid user id `%v` at line %d (%s)", user.UserId, lineCount, err.Error()))
 				return
@@ -1131,14 +1130,14 @@ func (m *Master) importExportItems(response http.ResponseWriter, request *http.R
 				return
 			}
 			// validate item id
-			if err = base.ValidateId(item.ItemId); err != nil {
+			if err = util.ValidateId(item.ItemId); err != nil {
 				server.BadRequest(restful.NewResponse(response),
 					fmt.Errorf("invalid item id `%v` at line %d (%s)", item.ItemId, lineCount, err.Error()))
 				return
 			}
 			// validate categories
 			for _, category := range item.Categories {
-				if err = base.ValidateId(category); err != nil {
+				if err = util.ValidateId(category); err != nil {
 					server.BadRequest(restful.NewResponse(response),
 						fmt.Errorf("invalid category `%v` at line %d (%s)", category, lineCount, err.Error()))
 					return
@@ -1243,19 +1242,19 @@ func (m *Master) importExportFeedback(response http.ResponseWriter, request *htt
 				return
 			}
 			// validate feedback type
-			if err = base.ValidateId(feedback.FeedbackType); err != nil {
+			if err = util.ValidateId(feedback.FeedbackType); err != nil {
 				server.BadRequest(restful.NewResponse(response),
 					fmt.Errorf("invalid feedback type `%v` at line %d (%s)", feedback.FeedbackType, lineCount, err.Error()))
 				return
 			}
 			// validate user id
-			if err = base.ValidateId(feedback.UserId); err != nil {
+			if err = util.ValidateId(feedback.UserId); err != nil {
 				server.BadRequest(restful.NewResponse(response),
 					fmt.Errorf("invalid user id `%v` at line %d (%s)", feedback.UserId, lineCount, err.Error()))
 				return
 			}
 			// validate item id
-			if err = base.ValidateId(feedback.ItemId); err != nil {
+			if err = util.ValidateId(feedback.ItemId); err != nil {
 				server.BadRequest(restful.NewResponse(response),
 					fmt.Errorf("invalid item id `%v` at line %d (%s)", feedback.ItemId, lineCount, err.Error()))
 				return
diff --git a/master/rpc_test.go b/master/rpc_test.go
index c0be61613..2d5a8f0a3 100644
--- a/master/rpc_test.go
+++ b/master/rpc_test.go
@@ -24,7 +24,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/gorse-io/gorse/base"
 	"github.com/gorse-io/gorse/common/monitor"
 	"github.com/gorse-io/gorse/common/util"
 	"github.com/gorse-io/gorse/config"
@@ -48,10 +47,10 @@ func newRankingDataset() (*dataset.Dataset, *dataset.Dataset) {
 }
 
 func newClickDataset() (*ctr.Dataset, *ctr.Dataset) {
-	dataset := &ctr.Dataset{
-		Index: base.NewUnifiedMapIndexBuilder().Build(),
+	dataSet := &ctr.Dataset{
+		Index: dataset.NewUnifiedMapIndexBuilder().Build(),
 	}
-	return dataset, dataset
+	return dataSet, dataSet
 }
 
 type mockMasterRPC struct {
diff --git a/master/tasks.go b/master/tasks.go
index db44b6eab..db3c16c80 100644
--- a/master/tasks.go
+++ b/master/tasks.go
@@ -25,7 +25,6 @@ import (
 	"github.com/c-bata/goptuna"
 	"github.com/c-bata/goptuna/tpe"
 	mapset "github.com/deckarep/golang-set/v2"
-	"github.com/gorse-io/gorse/base"
 	"github.com/gorse-io/gorse/common/expression"
 	"github.com/gorse-io/gorse/common/log"
 	"github.com/gorse-io/gorse/common/monitor"
@@ -275,7 +274,7 @@ func (m *Master) LoadDataFromDatabase(
 	// STEP 1: pull users
 	userLabelCount := make(map[string]int)
 	userLabelFirst := make(map[string]int32)
-	userLabelIndex := base.NewMapIndex()
+	userLabelIndex := dataset.NewMapIndex()
 	userLabels := make([][]lo.Tuple2[int32, float32], 0, estimatedNumUsers)
 	start := time.Now()
 	userChan, errChan := database.GetUserStream(newCtx, batchSize)
@@ -327,9 +326,9 @@ func (m *Master) LoadDataFromDatabase(
 	var items []data.Item
 	itemLabelCount := make(map[string]int)
 	itemLabelFirst := make(map[string]int32)
-	itemLabelIndex := base.NewMapIndex()
+	itemLabelIndex := dataset.NewMapIndex()
 	itemLabels := make([][]lo.Tuple2[int32, float32], 0, estimatedNumItems)
-	itemEmbeddingIndexer := base.NewMapIndex()
+	itemEmbeddingIndexer := dataset.NewMapIndex()
 	itemEmbeddingDimension := make([]map[int]int, 0)
 	itemEmbeddings := make([][][]float32, 0, estimatedNumItems)
 	start = time.Now()
@@ -429,11 +428,11 @@ func (m *Master) LoadDataFromDatabase(
 			for _, f := range feedback {
 				// convert user and item id to index
 				userIndex := dataSet.GetUserDict().Id(f.UserId)
-				if userIndex == base.NotId {
+				if userIndex == dataset.NotId {
 					continue
 				}
 				itemIndex := dataSet.GetItemDict().Id(f.ItemId)
-				if itemIndex == base.NotId {
+				if itemIndex == dataset.NotId {
 					continue
 				}
 				// insert feedback to positive set
@@ -514,11 +513,11 @@ func (m *Master) LoadDataFromDatabase(
 		for feedback := range feedbackChan {
 			for _, f := range feedback {
 				userIndex := dataSet.GetUserDict().Id(f.UserId)
-				if userIndex == base.NotId {
+				if userIndex == dataset.NotId {
 					continue
 				}
 				itemIndex := dataSet.GetItemDict().Id(f.ItemId)
-				if itemIndex == base.NotId {
+				if itemIndex == dataset.NotId {
 					continue
 				}
 				negativeSet[userIndex].Add(itemIndex)
@@ -544,7 +543,7 @@ func (m *Master) LoadDataFromDatabase(
 
 	// STEP 5: create click-through rate dataset
 	start = time.Now()
-	unifiedIndex := base.NewUnifiedMapIndexBuilder()
+	unifiedIndex := dataset.NewUnifiedMapIndexBuilder()
 	unifiedIndex.ItemIndex = dataSet.GetItemDict().ToIndex()
 	unifiedIndex.UserIndex = dataSet.GetUserDict().ToIndex()
 	unifiedIndex.ItemLabelIndex = itemLabelIndex
@@ -1120,7 +1119,7 @@ func (m *Master) collectGarbage(ctx context.Context, dataSet *dataset.Dataset) e
 				log.Logger().Error("invalid subset", zap.String("subset", subset))
 				return nil
 			}
-			if dataSet.GetUserDict().Id(splits[1]) == base.NotId || !lo.ContainsBy(m.Config.Recommend.UserToUser, func(cfg config.UserToUserConfig) bool {
+			if dataSet.GetUserDict().Id(splits[1]) == dataset.NotId || !lo.ContainsBy(m.Config.Recommend.UserToUser, func(cfg config.UserToUserConfig) bool {
 				return cfg.Name == splits[0]
 			}) {
 				return m.CacheClient.DeleteScores(ctx, []string{cache.UserToUser}, cache.ScoreCondition{
@@ -1134,7 +1133,7 @@ func (m *Master) collectGarbage(ctx context.Context, dataSet *dataset.Dataset) e
 				log.Logger().Error("invalid subset", zap.String("subset", subset))
 				return nil
 			}
-			if dataSet.GetItemDict().Id(splits[1]) == base.NotId || !lo.ContainsBy(m.Config.Recommend.ItemToItem, func(cfg config.ItemToItemConfig) bool {
+			if dataSet.GetItemDict().Id(splits[1]) == dataset.NotId || !lo.ContainsBy(m.Config.Recommend.ItemToItem, func(cfg config.ItemToItemConfig) bool {
 				return cfg.Name == splits[0]
 			}) {
 				return m.CacheClient.DeleteScores(ctx, []string{cache.ItemToItem}, cache.ScoreCondition{
@@ -1143,7 +1142,7 @@ func (m *Master) collectGarbage(ctx context.Context, dataSet *dataset.Dataset) e
 				})
 			}
 		case cache.CollaborativeFiltering:
-			if dataSet.GetUserDict().Id(subset) == base.NotId {
+			if dataSet.GetUserDict().Id(subset) == dataset.NotId {
 				return m.CacheClient.DeleteScores(ctx, []string{cache.CollaborativeFiltering}, cache.ScoreCondition{
 					Subset: lo.ToPtr(subset),
 					Before: lo.ToPtr(dataSet.GetTimestamp()),
diff --git a/model/cf/model.go b/model/cf/model.go
index 4cfe0f3e5..6fbdfca14 100644
--- a/model/cf/model.go
+++ b/model/cf/model.go
@@ -26,13 +26,12 @@ import (
 	"github.com/c-bata/goptuna"
 	"github.com/chewxy/math32"
 	mapset "github.com/deckarep/golang-set/v2"
-	"github.com/gorse-io/gorse/base"
-	"github.com/gorse-io/gorse/base/copier"
 	"github.com/gorse-io/gorse/common/encoding"
 	"github.com/gorse-io/gorse/common/floats"
 	"github.com/gorse-io/gorse/common/log"
 	"github.com/gorse-io/gorse/common/monitor"
 	"github.com/gorse-io/gorse/common/parallel"
+	"github.com/gorse-io/gorse/common/util"
 	"github.com/gorse-io/gorse/dataset"
 	"github.com/gorse-io/gorse/model"
 	"github.com/gorse-io/gorse/protocol"
@@ -301,17 +300,6 @@ func (baseModel *BaseMatrixFactorization) Invalid() bool {
 		baseModel.UserFactor == nil
 }
 
-// Clone a model with deep copy.
-func Clone(m MatrixFactorization) MatrixFactorization {
-	var copied MatrixFactorization
-	if err := copier.Copy(&copied, m); err != nil {
-		panic(err)
-	} else {
-		copied.SetParams(copied.GetParams())
-		return copied
-	}
-}
-
 func GetModelName(m Model) string {
 	switch m.(type) {
 	case *BPR:
@@ -419,13 +407,13 @@ func (bpr *BPR) Fit(ctx context.Context, trainSet, valSet dataset.CFSplit, confi
 		zap.Any("config", config))
 	bpr.Init(trainSet)
 	// Create buffers
-	temp := base.NewMatrix32(config.Jobs, bpr.nFactors)
-	userFactor := base.NewMatrix32(config.Jobs, bpr.nFactors)
-	positiveItemFactor := base.NewMatrix32(config.Jobs, bpr.nFactors)
-	negativeItemFactor := base.NewMatrix32(config.Jobs, bpr.nFactors)
-	rng := make([]base.RandomGenerator, config.Jobs)
+	temp := util.NewMatrix32(config.Jobs, bpr.nFactors)
+	userFactor := util.NewMatrix32(config.Jobs, bpr.nFactors)
+	positiveItemFactor := util.NewMatrix32(config.Jobs, bpr.nFactors)
+	negativeItemFactor := util.NewMatrix32(config.Jobs, bpr.nFactors)
+	rng := make([]util.RandomGenerator, config.Jobs)
 	for i := 0; i < config.Jobs; i++ {
-		rng[i] = base.NewRandomGenerator(bpr.GetRandomGenerator().Int63())
+		rng[i] = util.NewRandomGenerator(bpr.GetRandomGenerator().Int63())
 	}
 	// Convert array to hashmap
 	userFeedback := make([]mapset.Set[int32], trainSet.CountUsers())
@@ -604,7 +592,7 @@ func (als *ALS) Fit(ctx context.Context, trainSet, valSet dataset.CFSplit, confi
 		zap.Any("config", config))
 	als.Init(trainSet)
 	// Create temporary matrix
-	s := base.NewMatrix32(als.nFactors, als.nFactors)
+	s := util.NewMatrix32(als.nFactors, als.nFactors)
 	userPredictions := make([][]float32, config.Jobs)
 	itemPredictions := make([][]float32, config.Jobs)
 	userRes := make([][]float32, config.Jobs)
diff --git a/model/ctr/data.go b/model/ctr/data.go
index 4ac3dd15c..d6744626e 100644
--- a/model/ctr/data.go
+++ b/model/ctr/data.go
@@ -22,8 +22,9 @@ import (
 	"strings"
 
 	mapset "github.com/deckarep/golang-set/v2"
-	"github.com/gorse-io/gorse/base"
-	"github.com/gorse-io/gorse/base/jsonutil"
+	"github.com/gorse-io/gorse/common/jsonutil"
+	"github.com/gorse-io/gorse/common/util"
+	"github.com/gorse-io/gorse/dataset"
 	"github.com/gorse-io/gorse/model"
 	"github.com/juju/errors"
 	"github.com/samber/lo"
@@ -139,7 +140,7 @@ func convertEmbeddings(result []Embedding, prefix string, o any) []Embedding {
 
 // Dataset for click-through-rate models.
 type Dataset struct {
-	Index                  base.UnifiedIndex
+	Index                  dataset.UnifiedIndex
 	UserLabels             [][]lo.Tuple2[int32, float32]
 	ItemLabels             [][]lo.Tuple2[int32, float32]
 	ContextLabels          [][]lo.Tuple2[int32, float32]
@@ -148,7 +149,7 @@ type Dataset struct {
 	Target                 []float32
 	ItemEmbeddings         [][][]float32
 	ItemEmbeddingDimension []int
-	ItemEmbeddingIndex     *base.Index
+	ItemEmbeddingIndex     *dataset.Index
 	PositiveCount          int
 	NegativeCount          int
 }
@@ -183,7 +184,7 @@ func (dataset *Dataset) CountNegative() int {
 	return dataset.NegativeCount
 }
 
-func (dataset *Dataset) GetIndex() base.UnifiedIndex {
+func (dataset *Dataset) GetIndex() dataset.UnifiedIndex {
 	return dataset.Index
 }
 
@@ -314,7 +315,7 @@ func LoadDataFromBuiltIn(name string) (train, test *Dataset, err error) {
 	if test.ContextLabels, test.Target, testMaxLabel, err = LoadLibFMFile(testFilePath); err != nil {
 		return nil, nil, err
 	}
-	unifiedIndex := base.NewUnifiedDirectIndex(mathutil.MaxInt32(trainMaxLabel, testMaxLabel) + 1)
+	unifiedIndex := dataset.NewUnifiedDirectIndex(mathutil.MaxInt32(trainMaxLabel, testMaxLabel) + 1)
 	train.Index = unifiedIndex
 	test.Index = unifiedIndex
 	return
@@ -335,7 +336,7 @@ func (dataset *Dataset) Split(ratio float32, seed int64) (*Dataset, *Dataset) {
 	}
 	// split by random
 	numTestSize := int(float32(dataset.Count()) * ratio)
-	rng := base.NewRandomGenerator(seed)
+	rng := util.NewRandomGenerator(seed)
 	sampledIndex := mapset.NewSet(rng.Sample(0, dataset.Count(), numTestSize)...)
 	for i := 0; i < len(dataset.Target); i++ {
 		if sampledIndex.Contains(i) {
diff --git a/model/ctr/data_test.go b/model/ctr/data_test.go
index dfe2a0e89..6f09ba33b 100644
--- a/model/ctr/data_test.go
+++ b/model/ctr/data_test.go
@@ -18,7 +18,7 @@ import (
 	"fmt"
 	"testing"
 
-	"github.com/gorse-io/gorse/base"
+	"github.com/gorse-io/gorse/dataset"
 	"github.com/samber/lo"
 	"github.com/stretchr/testify/assert"
 )
@@ -111,14 +111,14 @@ func TestLoadDataFromBuiltIn(t *testing.T) {
 
 func TestDataset_Split(t *testing.T) {
 	// create dataset
-	unifiedIndex := base.NewUnifiedMapIndexBuilder()
-	dataset := NewMapIndexDataset()
+	unifiedIndex := dataset.NewUnifiedMapIndexBuilder()
+	dataSet := NewMapIndexDataset()
 	numUsers, numItems := 5, 6
 	for i := 0; i < numUsers; i++ {
 		unifiedIndex.AddUser(fmt.Sprintf("user%v", i))
 		unifiedIndex.AddUserLabel(fmt.Sprintf("user_label%v", 2*i))
 		unifiedIndex.AddUserLabel(fmt.Sprintf("user_label%v", 2*i+1))
-		dataset.UserLabels = append(dataset.UserLabels, []lo.Tuple2[int32, float32]{
+		dataSet.UserLabels = append(dataSet.UserLabels, []lo.Tuple2[int32, float32]{
 			{A: int32(2 * i), B: 1},
 			{A: int32(2*i + 1), B: 1},
 		})
@@ -128,7 +128,7 @@ func TestDataset_Split(t *testing.T) {
 		unifiedIndex.AddItemLabel(fmt.Sprintf("item_label%v", 3*i))
 		unifiedIndex.AddItemLabel(fmt.Sprintf("item_label%v", 3*i+1))
 		unifiedIndex.AddItemLabel(fmt.Sprintf("item_label%v", 3*i+2))
-		dataset.ItemLabels = append(dataset.ItemLabels, []lo.Tuple2[int32, float32]{
+		dataSet.ItemLabels = append(dataSet.ItemLabels, []lo.Tuple2[int32, float32]{
 			{A: int32(3 * i), B: 1},
 			{A: int32(3*i + 1), B: 1},
 			{A: int32(3*i + 2), B: 1},
@@ -137,44 +137,44 @@ func TestDataset_Split(t *testing.T) {
 	for i := 0; i < numUsers; i++ {
 		for j := 0; j < numItems; j++ {
 			if i+j > 4 {
-				dataset.Users = append(dataset.Users, int32(i))
-				dataset.Items = append(dataset.Items, int32(j))
-				dataset.ContextLabels = append(dataset.ContextLabels, []lo.Tuple2[int32, float32]{{A: int32(i * j), B: 0.5}})
-				dataset.Target = append(dataset.Target, 1)
-				dataset.PositiveCount++
+				dataSet.Users = append(dataSet.Users, int32(i))
+				dataSet.Items = append(dataSet.Items, int32(j))
+				dataSet.ContextLabels = append(dataSet.ContextLabels, []lo.Tuple2[int32, float32]{{A: int32(i * j), B: 0.5}})
+				dataSet.Target = append(dataSet.Target, 1)
+				dataSet.PositiveCount++
 			} else {
-				dataset.Users = append(dataset.Users, int32(i))
-				dataset.Items = append(dataset.Items, int32(j))
-				dataset.ContextLabels = append(dataset.ContextLabels, []lo.Tuple2[int32, float32]{{A: int32(i * j), B: 0.5}})
-				dataset.Target = append(dataset.Target, -1)
-				dataset.NegativeCount++
+				dataSet.Users = append(dataSet.Users, int32(i))
+				dataSet.Items = append(dataSet.Items, int32(j))
+				dataSet.ContextLabels = append(dataSet.ContextLabels, []lo.Tuple2[int32, float32]{{A: int32(i * j), B: 0.5}})
+				dataSet.Target = append(dataSet.Target, -1)
+				dataSet.NegativeCount++
 			}
 		}
 	}
-	dataset.Index = unifiedIndex.Build()
+	dataSet.Index = unifiedIndex.Build()
 
-	assert.Equal(t, numUsers*numItems, dataset.Count())
-	assert.Equal(t, numUsers, dataset.CountUsers())
-	assert.Equal(t, numItems, dataset.CountItems())
-	assert.Equal(t, numUsers*numItems/2, dataset.PositiveCount)
-	assert.Equal(t, numUsers*numItems/2, dataset.NegativeCount)
+	assert.Equal(t, numUsers*numItems, dataSet.Count())
+	assert.Equal(t, numUsers, dataSet.CountUsers())
+	assert.Equal(t, numItems, dataSet.CountItems())
+	assert.Equal(t, numUsers*numItems/2, dataSet.PositiveCount)
+	assert.Equal(t, numUsers*numItems/2, dataSet.NegativeCount)
 
-	features, values, target := dataset.Get(2)
+	features, values, target := dataSet.Get(2)
 	assert.Equal(t, []int32{
 		0,
-		dataset.Index.CountUsers() + 2,
-		dataset.Index.CountUsers() + dataset.Index.CountItems() + 0,
-		dataset.Index.CountUsers() + dataset.Index.CountItems() + 1,
-		dataset.Index.CountUsers() + dataset.Index.CountItems() + dataset.Index.CountUserLabels() + 6,
-		dataset.Index.CountUsers() + dataset.Index.CountItems() + dataset.Index.CountUserLabels() + 7,
-		dataset.Index.CountUsers() + dataset.Index.CountItems() + dataset.Index.CountUserLabels() + 8,
+		dataSet.Index.CountUsers() + 2,
+		dataSet.Index.CountUsers() + dataSet.Index.CountItems() + 0,
+		dataSet.Index.CountUsers() + dataSet.Index.CountItems() + 1,
+		dataSet.Index.CountUsers() + dataSet.Index.CountItems() + dataSet.Index.CountUserLabels() + 6,
+		dataSet.Index.CountUsers() + dataSet.Index.CountItems() + dataSet.Index.CountUserLabels() + 7,
+		dataSet.Index.CountUsers() + dataSet.Index.CountItems() + dataSet.Index.CountUserLabels() + 8,
 		0,
 	}, features)
 	assert.Equal(t, []float32{1, 1, 1, 1, 1, 1, 1, 0.5}, values)
 	assert.Equal(t, float32(-1), target)
 
 	// split
-	train, test := dataset.Split(0.2, 0)
+	train, test := dataSet.Split(0.2, 0)
 	assert.Equal(t, numUsers, train.CountUsers())
 	assert.Equal(t, numItems, train.CountItems())
 	assert.Equal(t, 24, train.Count())
diff --git a/model/ctr/model.go b/model/ctr/model.go
index 18615678b..7a25337d1 100644
--- a/model/ctr/model.go
+++ b/model/ctr/model.go
@@ -24,8 +24,6 @@ import (
 
 	"github.com/c-bata/goptuna"
 	"github.com/chewxy/math32"
-	"github.com/gorse-io/gorse/base"
-	"github.com/gorse-io/gorse/base/copier"
 	"github.com/gorse-io/gorse/common/encoding"
 	"github.com/gorse-io/gorse/common/log"
 	"github.com/gorse-io/gorse/common/monitor"
@@ -115,7 +113,7 @@ type FactorizationMachineSpawner interface {
 
 type BaseFactorizationMachines struct {
 	model.BaseModel
-	Index base.UnifiedIndex
+	Index dataset.UnifiedIndex
 }
 
 func (b *BaseFactorizationMachines) Init(trainSet dataset.CTRSplit) {
@@ -156,20 +154,6 @@ func UnmarshalModel(r io.Reader) (FactorizationMachines, error) {
 	return nil, fmt.Errorf("unknown model: %v", header)
 }
 
-// Clone a model with deep copy.
-func Clone(m FactorizationMachines) FactorizationMachines {
-	if cloner, ok := m.(FactorizationMachineCloner); ok {
-		return cloner.Clone()
-	}
-	var copied FactorizationMachines
-	if err := copier.Copy(&copied, m); err != nil {
-		panic(err)
-	} else {
-		copied.SetParams(copied.GetParams())
-		return copied
-	}
-}
-
 func Spawn(m FactorizationMachines) FactorizationMachines {
 	if cloner, ok := m.(FactorizationMachineSpawner); ok {
 		return cloner.Spawn()
@@ -285,25 +269,25 @@ func (fm *FMV2) BatchPredict(inputs []lo.Tuple4[string, string, []Label, []Label
 	x := make([]lo.Tuple2[[]int32, []float32], len(inputs))
 	for i, input := range inputs {
 		// encode user
-		if userIndex := fm.Index.EncodeUser(input.A); userIndex != base.NotId {
+		if userIndex := fm.Index.EncodeUser(input.A); userIndex != dataset.NotId {
 			x[i].A = append(x[i].A, userIndex)
 			x[i].B = append(x[i].B, 1)
 		}
 		// encode item
-		if itemIndex := fm.Index.EncodeItem(input.B); itemIndex != base.NotId {
+		if itemIndex := fm.Index.EncodeItem(input.B); itemIndex != dataset.NotId {
 			x[i].A = append(x[i].A, itemIndex)
 			x[i].B = append(x[i].B, 1)
 		}
 		// encode user labels
 		for _, userFeature := range input.C {
-			if userFeatureIndex := fm.Index.EncodeUserLabel(userFeature.Name); userFeatureIndex != base.NotId {
+			if userFeatureIndex := fm.Index.EncodeUserLabel(userFeature.Name); userFeatureIndex != dataset.NotId {
 				x[i].A = append(x[i].A, userFeatureIndex)
 				x[i].B = append(x[i].B, userFeature.Value)
 			}
 		}
 		// encode item labels
 		for _, itemFeature := range input.D {
-			if itemFeatureIndex := fm.Index.EncodeItemLabel(itemFeature.Name); itemFeatureIndex != base.NotId {
+			if itemFeatureIndex := fm.Index.EncodeItemLabel(itemFeature.Name); itemFeatureIndex != dataset.NotId {
 				x[i].A = append(x[i].A, itemFeatureIndex)
 				x[i].B = append(x[i].B, itemFeature.Value)
 			}
@@ -400,7 +384,7 @@ func (fm *FMV2) Marshal(w io.Writer) error {
 		return errors.Trace(err)
 	}
 	// write index
-	if err := base.MarshalUnifiedIndex(w, fm.Index); err != nil {
+	if err := dataset.MarshalUnifiedIndex(w, fm.Index); err != nil {
 		return errors.Trace(err)
 	}
 	// write dataset stats
@@ -425,7 +409,7 @@ func (fm *FMV2) Unmarshal(r io.Reader) error {
 	}
 	fm.SetParams(fm.Params)
 	// read index
-	fm.Index, err = base.UnmarshalUnifiedIndex(r)
+	fm.Index, err = dataset.UnmarshalUnifiedIndex(r)
 	if err != nil {
 		return errors.Trace(err)
 	}
diff --git a/model/ctr/optimize_test.go b/model/ctr/optimize_test.go
index 92d17f7f0..c12baa12e 100644
--- a/model/ctr/optimize_test.go
+++ b/model/ctr/optimize_test.go
@@ -20,7 +20,6 @@ import (
 
 	"github.com/c-bata/goptuna"
 	"github.com/c-bata/goptuna/tpe"
-	"github.com/gorse-io/gorse/base"
 	"github.com/gorse-io/gorse/dataset"
 	"github.com/gorse-io/gorse/model"
 	"github.com/samber/lo"
@@ -30,7 +29,7 @@ import (
 // NewMapIndexDataset creates a data set.
 func NewMapIndexDataset() *Dataset {
 	s := new(Dataset)
-	s.Index = base.NewUnifiedDirectIndex(0)
+	s.Index = dataset.NewUnifiedDirectIndex(0)
 	return s
 }
 
@@ -46,11 +45,11 @@ func (m *mockFactorizationMachineForSearch) Invalid() bool {
 	panic("implement me")
 }
 
-func (m *mockFactorizationMachineForSearch) GetUserIndex() base.Index {
+func (m *mockFactorizationMachineForSearch) GetUserIndex() dataset.Index {
 	panic("don't call me")
 }
 
-func (m *mockFactorizationMachineForSearch) GetItemIndex() base.Index {
+func (m *mockFactorizationMachineForSearch) GetItemIndex() dataset.Index {
 	panic("don't call me")
 }
 
diff --git a/model/model.go b/model/model.go
index cf76687ae..55dc7e451 100644
--- a/model/model.go
+++ b/model/model.go
@@ -16,7 +16,7 @@ package model
 
 import (
 	"github.com/c-bata/goptuna"
-	"github.com/gorse-io/gorse/base"
+	"github.com/gorse-io/gorse/common/util"
 )
 
 // Model is the interface for all models. Any model in this
@@ -33,7 +33,7 @@ type Model interface {
 // ID sets, random generator and fitting options are managed the BaseModel model.
 type BaseModel struct {
 	Params    Params               // Hyper-parameters
-	rng       base.RandomGenerator // Random generator
+	rng       util.RandomGenerator // Random generator
 	randState int64                // Random seed
 }
 
@@ -41,7 +41,7 @@ type BaseModel struct {
 func (model *BaseModel) SetParams(params Params) {
 	model.Params = params
 	model.randState = model.Params.GetInt64(RandomState, 0)
-	model.rng = base.NewRandomGenerator(model.randState)
+	model.rng = util.NewRandomGenerator(model.randState)
 }
 
 // GetParams returns all hyper-parameters.
@@ -49,6 +49,6 @@ func (model *BaseModel) GetParams() Params {
 	return model.Params
 }
 
-func (model *BaseModel) GetRandomGenerator() base.RandomGenerator {
+func (model *BaseModel) GetRandomGenerator() util.RandomGenerator {
 	return model.rng
 }
diff --git a/server/server.go b/server/server.go
index 4049692c4..6a16f7960 100644
--- a/server/server.go
+++ b/server/server.go
@@ -27,7 +27,6 @@ import (
 	"time"
 
 	"github.com/emicklei/go-restful/v3"
-	"github.com/gorse-io/gorse/base"
 	"github.com/gorse-io/gorse/cmd/version"
 	"github.com/gorse-io/gorse/common/log"
 	"github.com/gorse-io/gorse/common/util"
@@ -146,7 +145,7 @@ func (s *Server) Shutdown() {
 
 // Sync this server to the master.
 func (s *Server) Sync() {
-	defer base.CheckPanic()
+	defer util.CheckPanic()
 	log.Logger().Info("start meta sync", zap.Duration("meta_timeout", s.Config.Master.MetaTimeout))
 	for {
 		var meta *protocol.Meta
diff --git a/storage/data/database.go b/storage/data/database.go
index a24210e5b..aa715c7e4 100644
--- a/storage/data/database.go
+++ b/storage/data/database.go
@@ -25,8 +25,8 @@ import (
 	"time"
 
 	"github.com/XSAM/otelsql"
-	"github.com/gorse-io/gorse/base/jsonutil"
 	"github.com/gorse-io/gorse/common/expression"
+	"github.com/gorse-io/gorse/common/jsonutil"
 	"github.com/gorse-io/gorse/common/log"
 	"github.com/gorse-io/gorse/storage"
 	"github.com/juju/errors"
@@ -122,9 +122,9 @@ type ItemPatch struct {
 
 // User stores meta data about user.
 type User struct {
-	UserId    string `gorm:"primaryKey" mapstructure:"user_id"`
-	Labels    any    `gorm:"serializer:json" mapstructure:"labels"`
-	Comment   string `mapstructure:"comment"`
+	UserId  string `gorm:"primaryKey" mapstructure:"user_id"`
+	Labels  any    `gorm:"serializer:json" mapstructure:"labels"`
+	Comment string `mapstructure:"comment"`
 }
 
 // UserPatch is the modification on a user.
diff --git a/storage/data/sql.go b/storage/data/sql.go
index a1a3369e9..7d6bc5b8b 100644
--- a/storage/data/sql.go
+++ b/storage/data/sql.go
@@ -23,8 +23,8 @@ import (
 
 	mapset "github.com/deckarep/golang-set/v2"
 	_ "github.com/go-sql-driver/mysql"
-	"github.com/gorse-io/gorse/base/jsonutil"
 	"github.com/gorse-io/gorse/common/expression"
+	"github.com/gorse-io/gorse/common/jsonutil"
 	"github.com/gorse-io/gorse/common/log"
 	"github.com/gorse-io/gorse/storage"
 	"github.com/juju/errors"
diff --git a/worker/worker.go b/worker/worker.go
index bbc8f801a..2e1e43dea 100644
--- a/worker/worker.go
+++ b/worker/worker.go
@@ -30,7 +30,6 @@ import (
 	"time"
 
 	mapset "github.com/deckarep/golang-set/v2"
-	"github.com/gorse-io/gorse/base"
 	"github.com/gorse-io/gorse/cmd/version"
 	"github.com/gorse-io/gorse/common/expression"
 	"github.com/gorse-io/gorse/common/heap"
@@ -136,7 +135,7 @@ func NewWorker(
 	return &Worker{
 		rankers:       make([]ctr.FactorizationMachines, jobs),
 		Settings:      config.NewSettings(),
-		randGenerator: base.NewRand(time.Now().UTC().UnixNano()),
+		randGenerator: util.NewRand(time.Now().UTC().UnixNano()),
 		// config
 		cacheFile:  cacheFile,
 		masterHost: masterHost,
@@ -161,7 +160,7 @@ func (w *Worker) SetOneMode(settings *config.Settings) {
 
 // Sync this worker to the master.
 func (w *Worker) Sync() {
-	defer base.CheckPanic()
+	defer util.CheckPanic()
 	log.Logger().Info("start meta sync", zap.Duration("meta_timeout", w.Config.Master.MetaTimeout))
 	for {
 		var meta *protocol.Meta
@@ -272,7 +271,7 @@ func (w *Worker) Sync() {
 
 // Pull user index and ranking model from master.
 func (w *Worker) Pull() {
-	defer base.CheckPanic()
+	defer util.CheckPanic()
 	for range w.syncedChan.C {
 		pulled := false
 
@@ -511,7 +510,7 @@ func (w *Worker) Recommend(users []data.User) {
 	defer span.End()
 
 	go func() {
-		defer base.CheckPanic()
+		defer util.CheckPanic()
 		completedCount, previousCount := 0, 0
 		ticker := time.NewTicker(10 * time.Second)
 		for {
diff --git a/worker/worker_test.go b/worker/worker_test.go
index 6d6abe045..62d784fb7 100644
--- a/worker/worker_test.go
+++ b/worker/worker_test.go
@@ -30,7 +30,6 @@ import (
 
 	"github.com/c-bata/goptuna"
 	mapset "github.com/deckarep/golang-set/v2"
-	"github.com/gorse-io/gorse/base"
 	"github.com/gorse-io/gorse/common/expression"
 	"github.com/gorse-io/gorse/common/monitor"
 	"github.com/gorse-io/gorse/common/parallel"
@@ -531,10 +530,10 @@ func newRankingDataset() (*dataset.Dataset, *dataset.Dataset) {
 }
 
 func newClickDataset() (*ctr.Dataset, *ctr.Dataset) {
-	dataset := &ctr.Dataset{
-		Index: base.NewUnifiedMapIndexBuilder().Build(),
+	dataSet := &ctr.Dataset{
+		Index: dataset.NewUnifiedMapIndexBuilder().Build(),
 	}
-	return dataset, dataset
+	return dataSet, dataSet
 }
 
 type mockMaster struct {
@@ -572,7 +571,7 @@ func newMockMaster(t *testing.T) *mockMaster {
 
 	// create user index
 	userIndexBuffer := bytes.NewBuffer(nil)
-	err = base.MarshalIndex(userIndexBuffer, base.NewMapIndex())
+	err = dataset.MarshalIndex(userIndexBuffer, dataset.NewMapIndex())
 	assert.NoError(t, err)
 
 	return &mockMaster{