Index: compiler-rt/lib/fuzzer/FuzzerDriver.cpp
===================================================================
--- compiler-rt/lib/fuzzer/FuzzerDriver.cpp
+++ compiler-rt/lib/fuzzer/FuzzerDriver.cpp
@@ -870 +870,2 @@
-    FuzzWithFork(F->GetMD().GetRand(), Options, Args, *Inputs, Flags.fork);
+    FuzzWithFork(F->GetMD().GetRand(), Options, Args, *Inputs, Flags.fork,
+		 Flags.group);
Index: compiler-rt/lib/fuzzer/FuzzerFlags.def
===================================================================
--- compiler-rt/lib/fuzzer/FuzzerFlags.def
+++ compiler-rt/lib/fuzzer/FuzzerFlags.def
@@ -58,0 +59,2 @@
+FUZZER_FLAG_INT(group, 1, "FOR fork mode. Divide the main corpus into N groups "
+		"according to size.")
Index: compiler-rt/lib/fuzzer/FuzzerFork.h
===================================================================
--- compiler-rt/lib/fuzzer/FuzzerFork.h
+++ compiler-rt/lib/fuzzer/FuzzerFork.h
@@ -21 +21,2 @@
-                  const Vector<std::string> &CorpusDirs, int NumJobs);
+                  const Vector<std::string> &CorpusDirs, int NumJobs,
+		  int Group);
Index: compiler-rt/lib/fuzzer/FuzzerFork.cpp
===================================================================
--- compiler-rt/lib/fuzzer/FuzzerFork.cpp
+++ compiler-rt/lib/fuzzer/FuzzerFork.cpp
@@ -72 +72 @@
-  size_t      JobId;
+  size_t JobId;
@@ -74 +74 @@
-  int         DftTimeInSeconds = 0;
+  int DftTimeInSeconds = 0;
@@ -97,0 +98,2 @@
+  // Declare a variable to store the seed size.
+  Vector<std::size_t> FilesSizes;
@@ -117 +119 @@
-  FuzzJob *CreateNewJob(size_t JobId) {
+  FuzzJob *CreateNewJob(size_t JobId, int NumCorpuses, int Group) {
@@ -135,0 +138 @@
+    auto Time1 = std::chrono::system_clock::now();
@@ -137,11 +140,31 @@
-            std::min(Files.size(), (size_t)sqrt(Files.size() + 2))) {
-      auto Time1 = std::chrono::system_clock::now();
-      for (size_t i = 0; i < CorpusSubsetSize; i++) {
-        auto &SF = Files[Rand->SkewTowardsLast(Files.size())];
-        Seeds += (Seeds.empty() ? "" : ",") + SF;
-        CollectDFT(SF);
-      }
-      auto Time2 = std::chrono::system_clock::now();
-      auto DftTimeInSeconds = duration_cast<seconds>(Time2 - Time1).count();
-      assert(DftTimeInSeconds < std::numeric_limits<int>::max());
-      Job->DftTimeInSeconds = static_cast<int>(DftTimeInSeconds);
+                std::min(Files.size(), (size_t)sqrt(Files.size() + 2))){
+       if (Group) { // flag: whether to group the corpus.
+             size_t AverageCorpusSize = Files.size() / NumCorpuses + 1;
+             if (Files.size() == 0)
+                     AverageCorpusSize = 0;
+             size_t StartIndex = ((JobId - 1) % NumCorpuses) * AverageCorpusSize;
+             for (size_t i = 0; i < CorpusSubsetSize; i++) {
+                std::random_device rd;
+                std::mt19937 RandomSeed(rd());
+                std::uniform_int_distribution<> rand(0,AverageCorpusSize);
+                size_t RandNum = rand(RandomSeed);
+                size_t Index = RandNum + StartIndex;
+                if (Index < Files.size()) {
+                       auto &SF = Files[Index];
+               	    Seeds += (Seeds.empty() ? "" : ",") + SF;
+               	    CollectDFT(SF);
+                }
+                else  {
+                       auto &SF = Files[Rand->SkewTowardsLast(Files.size())];
+               	    Seeds += (Seeds.empty() ? "" : ",") + SF;
+               	    CollectDFT(SF);
+                }
+             }
+       }
+       else{
+               for (size_t i = 0; i < CorpusSubsetSize; i++) {
+               auto &SF = Files[Rand->SkewTowardsLast(Files.size())];
+               Seeds += (Seeds.empty() ? "" : ",") + SF;
+               CollectDFT(SF);
+               }
+       }
@@ -148,0 +172,5 @@
+    auto Time2 = std::chrono::system_clock::now();
+    auto DftTimeInSeconds = duration_cast<seconds>(Time2 - Time1).count();
+    assert(DftTimeInSeconds < std::numeric_limits<int>::max());
+    Job->DftTimeInSeconds = static_cast<int>(DftTimeInSeconds);
+
@@ -182 +210 @@
-  void RunOneMergeJob(FuzzJob *Job) {
+  void RunOneMergeJob(FuzzJob *Job, int Group) {
@@ -222 +250,10 @@
-      Files.push_back(NewPath);
+      if (Group) {// Insert the queue according to the size of the seed.
+	      long usz = U.size();
+	      auto idx = std::upper_bound(FilesSizes.begin(), FilesSizes.end(), usz) - 
+		      FilesSizes.begin();
+	      FilesSizes.insert(FilesSizes.begin() + idx, usz);
+	      Files.insert(Files.begin() + idx, NewPath);
+      }
+      else {
+	      Files.push_back(NewPath);
+      }
@@ -287 +324,2 @@
-                  const Vector<std::string> &CorpusDirs, int NumJobs) {
+                  const Vector<std::string> &CorpusDirs, int NumJobs,
+		  int Group) {
@@ -315 +353 @@
-    for (auto &File : SeedFiles)
+    for (auto &File : SeedFiles){
@@ -316,0 +355,2 @@
+      Env.FilesSizes.push_back(File.Size);
+    }
@@ -325,0 +366,7 @@
+
+  if (Group) {
+	  for (auto &path : Env.Files) {
+		  Env.FilesSizes.push_back(FileSize(path));
+	  }
+  }
+
@@ -328,0 +376 @@
+
@@ -339 +387,4 @@
-
+  
+  size_t MergeCycle = 20;
+  size_t JobExecuted = 0;
+  int NumCorpuses = 8;
@@ -344 +395 @@
-    FuzzQ.Push(Env.CreateNewJob(JobId++));
+    FuzzQ.Push(Env.CreateNewJob(JobId++, NumCorpuses, Group));
@@ -359 +410,29 @@
-    Env.RunOneMergeJob(Job.get());
+    Env.RunOneMergeJob(Job.get(), Group);
+    // merge the corpus .
+    JobExecuted ++;
+    if (Group) {
+        if(JobExecuted >= MergeCycle){
+               Vector<SizedFile> CurrentSeedFiles;
+               for (auto &Dir : CorpusDirs)
+                   GetSizedFilesFromDir(Dir, &CurrentSeedFiles);
+               std::sort(CurrentSeedFiles.begin(), CurrentSeedFiles.end());
+               if (CorpusDirs.empty())
+                   MkDir(Env.MainCorpusDir = DirPlusFile(Env.TempDir, "C"));
+               else
+                   Env.MainCorpusDir = CorpusDirs[0];
+
+               auto CFPath = DirPlusFile(Env.TempDir, "merge.txt");
+        	   Set<uint32_t> TmpNewFeatures, TmpNewCov;
+        	   Set<uint32_t> TmpFeatures, TmpCov;
+        	   Env.Files.clear();
+        	   Env.FilesSizes.clear();
+        	   CrashResistantMerge(Env.Args, {}, CurrentSeedFiles, &Env.Files, TmpFeatures,
+                                  &TmpNewFeatures, TmpCov, &TmpNewCov, CFPath, false);
+               for (auto &path : Env.Files) {
+            	   Env.FilesSizes.push_back(FileSize(path));
+               }
+               RemoveFile(CFPath);
+               JobExecuted = 0;
+               MergeCycle += 5;
+	}    
+    }
@@ -402 +481,20 @@
-    FuzzQ.Push(Env.CreateNewJob(JobId++));
+    // Since the number of corpus seeds will gradually increase, in order to
+    // control the number in each group to be about three times the number of
+    // seeds selected each time, the number of groups is dynamically adjusted.
+    if (Env.Files.size() >= 1 && Env.Files.size() < 1600)
+	    NumCorpuses = 16;
+    if (Env.Files.size() >= 1600 && Env.Files.size() < 3600)
+	    NumCorpuses = 20;
+    if (Env.Files.size() >= 3600 && Env.Files.size() < 6400)
+	    NumCorpuses = 24;
+    if (Env.Files.size() >= 6400 && Env.Files.size() < 8100)
+	    NumCorpuses = 32;
+    if (Env.Files.size() >= 8100 && Env.Files.size() < 12000)
+	    NumCorpuses = 36;
+    if (Env.Files.size() >= 12000 && Env.Files.size() < 16000)
+	    NumCorpuses = 40;
+    if (Env.Files.size() >= 16000 && Env.Files.size() < 30000)
+	    NumCorpuses = 60;
+    if(Env.Files.size() >= 30000)
+	    NumCorpuses = 80;
+    FuzzQ.Push(Env.CreateNewJob(JobId++, NumCorpuses, Group));
@@ -404 +501,0 @@
-