diff --git a/DRAMSys/simulator/resources/configs/mcconfigs/sms.xml b/DRAMSys/simulator/resources/configs/mcconfigs/sms.xml
index 088a9f66..f2ac6c19 100644
--- a/DRAMSys/simulator/resources/configs/mcconfigs/sms.xml
+++ b/DRAMSys/simulator/resources/configs/mcconfigs/sms.xml
@@ -1,7 +1,7 @@
 <mcconfig>
     <BankwiseLogic value="0"/>
     <OpenPagePolicy value="1" />
-    <MaxNrOfTransactions value="20" />
+    <MaxNrOfTransactions value="30" />
     <Scheduler value="SMS" />
     <SJFProbability value="50" />
     <RequestBufferSize value = "10" />
@@ -13,4 +13,4 @@
     <!-- Modes: NoStorage, Store (store data without errormodel), ErrorModel (store data with errormodel) -->
     <StoreMode value="NoStorage" />
     <ControllerCoreDisableRefresh value="0"/>
-</mcconfig>
\ No newline at end of file
+</mcconfig>
diff --git a/DRAMSys/simulator/resources/simulations/sms-example.xml b/DRAMSys/simulator/resources/simulations/sms-example.xml
index d40e0e8c..3b412664 100644
--- a/DRAMSys/simulator/resources/simulations/sms-example.xml
+++ b/DRAMSys/simulator/resources/simulations/sms-example.xml
@@ -12,14 +12,15 @@
     <mcconfig src="sms.xml"/>
 
     <tracesetup id="sms">
-      <device clkMhz="200">ddr3_example.stl</device>
+<!--      <device clkMhz="200">ddr3_example.stl</device>
       <device clkMhz="200">sms_t1.stl</device>
       <device clkMhz="200">sms_t2.stl</device>
       <device clkMhz="200">sms_t3.stl</device>
-      <device clkMhz="200">sms_t4.stl</device>
-      <device clkMhz="200">stream.stl</device>
-      <device clkMhz="200">random.stl</device>
-      <device clkMhz="200">chstone-adpcm_32.stl</device>
+      <device clkMhz="200">sms_t4.stl</device>-->
+
+      <device clkMhz="1000">random.stl</device>
+      <device clkMhz="1000">chstone-adpcm_32.stl</device>
+      <device clkMhz="1000">stream.stl</device>
     </tracesetup>
 
 </simulation>
diff --git a/DRAMSys/simulator/src/controller/scheduler/SMS.cpp b/DRAMSys/simulator/src/controller/scheduler/SMS.cpp
index 64882dc3..8eedea6a 100644
--- a/DRAMSys/simulator/src/controller/scheduler/SMS.cpp
+++ b/DRAMSys/simulator/src/controller/scheduler/SMS.cpp
@@ -61,15 +61,13 @@ void SMS::batchScheduler()
       multiBatchFormation(memClk);
       if (existReadyBatches()) {
         if (!isSystemLightlyLoaded() && (existLowIntensityThread() || distribution(generator))) {
-          if (pickSJF()) {
-            drain(memClk, (*lastSelectedThread).second.front());
-            (*lastSelectedThread).second.pop_front();
-          }
+          pickSJF();
+          drain(memClk);
+          (*lastSelectedThread).second.pop_front();
         } else {
-          if (pickRR()) {
-            drain(memClk, (*lastSelectedThread).second.front());
-            (*lastSelectedThread).second.pop_front();
-          }
+          pickRR();
+          drain(memClk);
+          (*lastSelectedThread).second.pop_front();
         }
       } else {
         wait(memClk);
@@ -87,7 +85,7 @@ bool SMS::pickSJF()
 {
   // find threads with ready batches
   std::vector<Thread> threadsWithReadyBatches;
-  for (auto& each : readyBatchIters)
+  for (const auto &each : readyBatchIters)
   {
     if (!each.second.empty())
     {
@@ -99,8 +97,8 @@ bool SMS::pickSJF()
   if (!threadsWithReadyBatches.empty())
   {
     // pick shortest-job thread among threads with non-empty request buffer
-    Thread minThread = threadsWithReadyBatches.front();
-    for (auto& thread : threadsWithReadyBatches)
+    Thread &minThread = threadsWithReadyBatches.front();
+    for (const auto &thread : threadsWithReadyBatches)
     {
       if (inFlightMemRequestCounter[thread] < inFlightMemRequestCounter[minThread])
       {
@@ -126,17 +124,19 @@ bool SMS::pickSJF()
  * @param memClk
  * @param last
  */
-void SMS::drain(sc_time memClk, std::deque<gp*>::iterator last)
+void SMS::drain(const sc_time &memClk)
 {
-  Thread selectedThread = (*lastSelectedThread).first;
+  if (lastSelectedThread->second.empty()) {
+        return;
+  }
+  const Thread &selectedThread = lastSelectedThread->first;
+  const std::deque<gp*>::iterator &last = lastSelectedThread->second.front();
+  assert(last != requestBuffers[selectedThread].end());
   unsigned int batchSize = std::distance(requestBuffers[selectedThread].begin(), last) + 1;
+  assert(batchSize > 0 && batchSize <= requestBuffers[selectedThread].size());
   for (unsigned int i = 1; i <= batchSize; i++)
   {
     Bank bank = DramExtension::getExtension(requestBuffers[selectedThread].front()).getBank();
-    //  if(bankBuffers[bank].size() == Configuration::getInstance().BankBufferSize)
-    //  {
-    //    wait(bankBufferIsNotFull);
-    //  }
     wait(memClk);
     bankBuffers[bank].emplace_back(requestBuffers[selectedThread].front());
     requestBuffers[selectedThread].pop_front();
@@ -155,54 +155,42 @@ void SMS::drain(sc_time memClk, std::deque<gp*>::iterator last)
  */
 bool SMS::pickRR()
 {
-  std::map<Thread, std::deque<gp_deque_iterator>>::iterator nextSelectedThread;
-  if (lastSelectedThread == readyBatchIters.end())
-  {
-    lastSelectedThread = readyBatchIters.begin();
-    nextSelectedThread = lastSelectedThread;
-  }
-  else
-  {
-    nextSelectedThread = lastSelectedThread;
-    nextSelectedThread++;
-    if (nextSelectedThread == readyBatchIters.end())
-      nextSelectedThread = readyBatchIters.begin();
-  }
-
-  std::map<Thread, std::deque<gp_deque_iterator>>::iterator savedOriginalNextSelectedThread = nextSelectedThread;
-
-  while ((*nextSelectedThread).second.empty())
-  {
-    nextSelectedThread++;
-    if (nextSelectedThread == readyBatchIters.end())
+    if (lastSelectedThread == readyBatchIters.end())
     {
-      nextSelectedThread = readyBatchIters.begin();
+      lastSelectedThread = readyBatchIters.begin();
+      if (!(*lastSelectedThread).second.empty()) {
+          return true;
+      }
     }
 
-    if (nextSelectedThread == savedOriginalNextSelectedThread)
+    std::map<Thread, std::deque<gp_deque_iterator>>::iterator savedOriginalNextSelectedThread = lastSelectedThread;
+
+    do
     {
-      // the next thread is the original thread, that mean req buffer are totally empty
-      // non-existed ready batch to be picked up & drained
-      return false;
-    }
-  }
-  // save last selected thread
-  lastSelectedThread = nextSelectedThread;
-  debugManager.printDebugMessage(name(),
-      "[RR] Select ready batch of thread " + to_string((*nextSelectedThread).first.ID()));
-  return true;
+      lastSelectedThread++;
+      if (lastSelectedThread == readyBatchIters.end()) {
+        lastSelectedThread = readyBatchIters.begin();
+      }
+      if (lastSelectedThread == savedOriginalNextSelectedThread) {
+        return false;
+      }
+    } while ((*lastSelectedThread).second.empty());
+
+    debugManager.printDebugMessage(name(),
+        "[RR] Select ready batch of thread " + to_string((*lastSelectedThread).first.ID()));
+    return true;
 }
 
-bool SMS::isSystemLightlyLoaded() {
+bool SMS::isSystemLightlyLoaded() const {
   unsigned int totalRequest = 0;
-  for (auto& bankBuffer : bankBuffers) {
+  for (const auto &bankBuffer : bankBuffers) {
     totalRequest += bankBuffer.second.size();
   }
   return (totalRequest <= LOW_SYSTEM_LOAD);
 }
 
-bool SMS::existLowIntensityThread() {
-  for (auto& mpkcPerThread : MPKCs) {
+bool SMS::existLowIntensityThread() const {
+  for (const auto &mpkcPerThread : MPKCs) {
     if (mpkcPerThread.second < LOW_MPKC) {
       return true;
     }
@@ -210,7 +198,7 @@ bool SMS::existLowIntensityThread() {
   return false;
 }
 
-bool SMS::isThresholdAgeExceeded(Thread thread, sc_time memClk, std::deque<gp*>::iterator begin, std::deque<gp*>::iterator end) {
+bool SMS::isThresholdAgeExceeded(const Thread &thread, sc_time const &memClk, std::deque<gp*>::iterator const &begin, std::deque<gp*>::iterator const &end) {
   // find the oldest request in the thread's batch
   sc_time oldestGenerationTime = sc_time_stamp();
   for (auto reqIter = begin; reqIter != end; reqIter++) {
@@ -231,28 +219,28 @@ bool SMS::isThresholdAgeExceeded(Thread thread, sc_time memClk, std::deque<gp*>:
   }
 }
 
-void SMS::updateMPKCs(sc_time memClk) {
+void SMS::updateMPKCs(sc_time const &memClk) {
   if (sc_time_stamp() % (MPKC_RESET_CYCLE * memClk) <= memClk) {
     // reset for every 10k clk cycles
-    for (auto& cacheMiss : cacheMisses) {
+    for (const auto &cacheMiss : cacheMisses) {
       MPKCs[cacheMiss.first] = 0;
     }
     debugManager.printDebugMessage(name(), "Reset MKKCs");
   } else {
     // update MPKC for every thread
-    for (auto& cacheMiss : cacheMisses) {
+    for (const auto &cacheMiss : cacheMisses) {
       MPKCs[cacheMiss.first] = (cacheMiss.second * 1000.0 * memClk) / (sc_time_stamp());
     }
     debugManager.printDebugMessage(name(), "Update MPKCs");
   }
 }
 
-bool SMS::isExceededReqBufferSize(Thread thread) {
+bool SMS::isExceededReqBufferSize(Thread const &thread) {
   return requestBuffers[thread].size() == Configuration::getInstance().RequestBufferSize;
 }
 
-bool SMS::isRequestBuffersEmpty() {
-  for (auto& requestBuffer : requestBuffers) {
+bool SMS::isRequestBuffersEmpty() const {
+  for (const auto &requestBuffer : requestBuffers) {
     if (!requestBuffer.second.empty()) {
       return false;
     }
@@ -260,8 +248,8 @@ bool SMS::isRequestBuffersEmpty() {
   return true;
 }
 
-bool SMS::existReadyBatches() {
-  for (auto& each : readyBatchIters) {
+bool SMS::existReadyBatches() const {
+  for (const auto &each : readyBatchIters) {
     if (!each.second.empty()) {
       return true;
     }
@@ -276,46 +264,47 @@ bool SMS::existReadyBatches() {
  * @param begin
  * @return true if this batch is ready, otherwise false
  */
-bool SMS::batchFormation(sc_time memClk, std::pair<Thread, std::deque<gp*>> &requestBuffer,
-    std::deque<gp*>::iterator beginIter)
+bool SMS::batchFormation(sc_time const &memClk, Thread const &thread, std::deque<gp*> const &requestBuffer, std::deque<gp*>::iterator const &beginIter)
 {
-  if (requestBuffer.second.empty())
+  if (requestBuffer.empty())
   {
     return false;
   }
 
-  if (requestBuffer.second.end() == beginIter)
+  if (requestBuffer.end() == beginIter)
   {
     return false;
   }
 
-  if (MPKCs[requestBuffer.first] < LOW_MPKC || isSystemLightlyLoaded())
+  if (MPKCs[thread] < LOW_MPKC || isSystemLightlyLoaded())
   {
     // bypass requests by forming batch with only one request (threshold age is ZERO)
-    readyBatchIters[requestBuffer.first].push_back(beginIter);
+    readyBatchIters[thread].push_back(beginIter);
     return true;
   }
   else
   {
     // forming batch with FIFO size & threshold age constraints
-    auto firstDifferentRowAccessReqIter = beginIter;
+    std::deque<gp*>::iterator firstDifferentRowAccessReqIter = beginIter;
     Row firstRow = DramExtension::getRow(*beginIter);
-    while (firstDifferentRowAccessReqIter != requestBuffer.second.end()
+    while (firstDifferentRowAccessReqIter != requestBuffer.end()
         && DramExtension::getRow(*firstDifferentRowAccessReqIter) == firstRow)
     {
-      firstDifferentRowAccessReqIter++;
+      ++firstDifferentRowAccessReqIter;
+      if (firstDifferentRowAccessReqIter == requestBuffer.end ()) {
+          break;
+      }
     }
 
     // deem this batch ready
-    if ((firstDifferentRowAccessReqIter != requestBuffer.second.end())
-        || isExceededReqBufferSize(requestBuffer.first)
-        || isThresholdAgeExceeded(requestBuffer.first, memClk, beginIter,
-            firstDifferentRowAccessReqIter))
+    if ((firstDifferentRowAccessReqIter != requestBuffer.end())
+        || isExceededReqBufferSize(thread)
+        || isThresholdAgeExceeded(thread, memClk, beginIter, firstDifferentRowAccessReqIter))
     {
-      firstDifferentRowAccessReqIter--;
-      readyBatchIters[requestBuffer.first].push_back(firstDifferentRowAccessReqIter);
+      --firstDifferentRowAccessReqIter;
+      readyBatchIters[thread].push_back(firstDifferentRowAccessReqIter);
       debugManager.printDebugMessage(name(),
-          "Deem batch ready - thread " + to_string(requestBuffer.first.ID()));
+          "Deem batch ready - thread " + to_string(thread.ID()));
       return true;
     }
     else
@@ -325,29 +314,29 @@ bool SMS::batchFormation(sc_time memClk, std::pair<Thread, std::deque<gp*>> &req
   }
 }
 
-void SMS::multiBatchFormation(sc_time memClk)
+void SMS::multiBatchFormation(sc_time const &memClk)
 {
-  for (auto& requestBuffer : requestBuffers)
+  for (auto &requestBuffer : requestBuffers)
   {
     bool formed;
     do
     {
       if (readyBatchIters[requestBuffer.first].empty())
       {
-        formed = batchFormation(memClk, (std::pair<Thread, std::deque<gp*>>&)requestBuffer, requestBuffer.second.begin());
+        formed = batchFormation(memClk, requestBuffer.first, requestBuffer.second, requestBuffer.second.begin());
       }
       else
       {
-        formed = batchFormation(memClk, (std::pair<Thread, std::deque<gp*>>&)requestBuffer, readyBatchIters[requestBuffer.first].back() + 1);
+        formed = batchFormation(memClk, requestBuffer.first, requestBuffer.second, readyBatchIters[requestBuffer.first].back() + 1);
       }
-    } while (formed);
+    } while (!requestBuffer.second.empty() && formed);
   }
 }
 
 gp* SMS::getPendingRequest(Bank bank)
 {
-  for (auto& requestBuffer : requestBuffers) {
-    for (auto& request : requestBuffer.second) {
+  for (const auto &requestBuffer : requestBuffers) {
+    for (const auto &request : requestBuffer.second) {
       if (DramExtension::getBank(request) == bank) {
         return request;
       }
diff --git a/DRAMSys/simulator/src/controller/scheduler/SMS.h b/DRAMSys/simulator/src/controller/scheduler/SMS.h
index 2843b990..bdb5c783 100644
--- a/DRAMSys/simulator/src/controller/scheduler/SMS.h
+++ b/DRAMSys/simulator/src/controller/scheduler/SMS.h
@@ -65,20 +65,20 @@ private:
 
     DebugManager& debugManager;
 
-    bool batchFormation(sc_time memClk, std::pair<Thread, std::deque<gp*>> &requestBuffer, std::deque<gp*>::iterator beginIter);
-    void multiBatchFormation(sc_time memClk);
+    bool batchFormation(sc_time const &memClk, Thread const &thread, const std::deque<gp*> &requestBuffer, const std::deque<gp*>::iterator &beginIter);
+    void multiBatchFormation(const sc_time &memClk);
     bool pickSJF();
     bool pickRR();
-    void drain(sc_time memClk, std::deque<gp*>::iterator last);
+    void drain(const sc_time &memClk);
 
-    bool existLowIntensityThread();
-    bool isSystemLightlyLoaded();
-    bool isThresholdAgeExceeded(Thread thread, sc_time memClk,  std::deque<gp*>::iterator begin, std::deque<gp*>::iterator end);
-    bool isExceededReqBufferSize(Thread thread);
-    void updateMPKCs(sc_time memClk);
+    bool existLowIntensityThread() const;
+    bool isSystemLightlyLoaded() const;
+    bool isThresholdAgeExceeded(const Thread &thread, const sc_time &memClk,  const std::deque<gp*>::iterator &begin, const std::deque<gp*>::iterator &end);
+    bool isExceededReqBufferSize(Thread const &thread);
+    void updateMPKCs(const sc_time &memClk);
 
-    bool isRequestBuffersEmpty();
-    bool existReadyBatches();
+    bool isRequestBuffersEmpty() const;
+    bool existReadyBatches() const;
 };
 
 #endif // SMS_H