diff --git a/src/optimizer.go b/src/optimizer.go
index 8073c61..3a59c99 100644
--- a/src/optimizer.go
+++ b/src/optimizer.go
@@ -3,11 +3,14 @@ package main
 import (
 	log "github.com/sirupsen/logrus"
 	"sync"
+	"strings"
 )
 
 type Optimizer struct {
 	scheduler  Scheduler
 	killedFlag bool
+
+	predicts map[string]OptimizerJobExecutionTime
 }
 
 var optimizerInstance *Optimizer
@@ -19,11 +22,42 @@ func InstanceOfOptimizer() *Optimizer {
 
 	if optimizerInstance == nil {
 		optimizerInstance = &Optimizer{}
+		optimizerInstance.predicts = map[string]OptimizerJobExecutionTime{}
 	}
 	return optimizerInstance
 }
 
-func (jhl *Optimizer) feed(job string, utils []int) {
+func (optimizer *Optimizer) feed(job string, utils []int) {
 	log.Info("optimizer feed")
 	log.Info(job, utils)
+
+	go func() {
+		str := strings.Split(job, "-")
+		if len(str) == 2 {
+			preCnt := 0
+			for i := 0; i < len(utils); i++ {
+				if utils[i] > 15 {
+					break
+				}
+				preCnt++
+			}
+
+			postCnt := 0
+			for i := len(utils); i >= 0; i-- {
+				if utils[i] > 15 {
+					break
+				}
+				postCnt++
+			}
+
+			if _, ok := optimizer.predicts[str[0]]; !ok {
+				optimizer.predicts[str[0]] = OptimizerJobExecutionTime{}
+			}
+			predict := optimizer.predicts[str[0]]
+			predict.Pre = ((predict.Pre * predict.Version) + preCnt) / (predict.Version + 1)
+			predict.Post = ((predict.Post * predict.Version) + postCnt) / (predict.Version + 1)
+			predict.Total = ((predict.Total * predict.Version) + len(utils)) / (predict.Version + 1)
+			predict.Version++
+		}
+	}()
 }
diff --git a/src/resource_pool.go b/src/resource_pool.go
index 338e945..f2b769e 100644
--- a/src/resource_pool.go
+++ b/src/resource_pool.go
@@ -27,8 +27,9 @@ type ResourcePool struct {
 	counter      int
 	counterTotal int
 
-	bindings map[string]map[string]bool
-	utils    map[string][]int
+	bindings  map[string]map[string]bool
+	utils     map[string][]int
+	bindingMu sync.Mutex
 }
 
 func (pool *ResourcePool) start() {
@@ -210,6 +211,8 @@ func (pool *ResourcePool) releaseNetwork(network string) {
 }
 
 func (pool *ResourcePool) attach(GPU string, job string) {
+	pool.bindingMu.Lock()
+	defer pool.bindingMu.Unlock()
 	if _, ok := pool.bindings[GPU]; !ok {
 		pool.bindings[GPU] = map[string]bool{}
 	}
@@ -221,6 +224,8 @@ func (pool *ResourcePool) attach(GPU string, job string) {
 }
 
 func (pool *ResourcePool) detach(GPU string, jobName string) {
+	pool.bindingMu.Lock()
+	defer pool.bindingMu.Unlock()
 	if _, ok := pool.bindings[GPU]; ok {
 		if len(pool.bindings[GPU]) == 1 {
 			InstanceOfOptimizer().feed(jobName, pool.utils[GPU])
diff --git a/src/scheduler_fair.go b/src/scheduler_fair.go
index cd6f923..e0db6cf 100644
--- a/src/scheduler_fair.go
+++ b/src/scheduler_fair.go
@@ -206,6 +206,10 @@ func (scheduler *SchedulerFair) ReleaseResource(job Job, agent NodeStatus) {
 		for j := range nodes.Status {
 			if gpu.UUID == nodes.Status[j].UUID {
 				nodes.Status[j].MemoryAllocated -= gpu.MemoryTotal
+				if nodes.Status[j].MemoryAllocated < 0 {
+					// in case error
+					nodes.Status[j].MemoryAllocated = 0
+				}
 			}
 		}
 	}
@@ -376,4 +380,4 @@ func (scheduler *SchedulerFair) Attach(GPU string, job string) {
 
 func (scheduler *SchedulerFair) Detach(GPU string, job string) {
 	pool.detach(GPU, job)
-}
\ No newline at end of file
+}
diff --git a/src/util.go b/src/util.go
index 04f0323..871d850 100644
--- a/src/util.go
+++ b/src/util.go
@@ -111,7 +111,7 @@ type GPUStatus struct {
 type NodeStatus struct {
 	ClientID     string      `json:"id"`
 	ClientHost   string      `json:"host"`
-	Version      float64      `json:"version"`
+	Version      float64     `json:"version"`
 	NumCPU       int         `json:"cpu_num"`
 	UtilCPU      float64     `json:"cpu_load"`
 	MemTotal     int         `json:"mem_total"`
@@ -164,6 +164,13 @@ type MsgGroupList struct {
 	Groups []Group `json:"groups"`
 }
 
+type OptimizerJobExecutionTime struct {
+	Pre     int `json:"pre"`
+	Post    int `json:"post"`
+	Total   int `json:"total"`
+	Version int `json:"version"`
+}
+
 func str2int(str string, defaultValue int) int {
 	i, err := strconv.Atoi(str)
 	if err == nil {