diff --git a/trainer/include/Trainer.hpp b/trainer/include/Trainer.hpp
index 722508256cde75ca054f1853063302b728bcf43f..9a2f98528c65b4d788cf99d3a3a111f5378e6f54 100644
--- a/trainer/include/Trainer.hpp
+++ b/trainer/include/Trainer.hpp
@@ -40,6 +40,9 @@ class Trainer
   /// @brief If true, will print infos on stderr
   bool debugMode;
 
+  /// @brief If true, duplicates examples will be removed from the training set.
+  bool removeDuplicates;
+
   public :
 
   /// @brief The FeatureDescritpion of a Config.
@@ -109,7 +112,8 @@ void processAllExamples(
   /// @param bd The BD to use.
   /// @param config The config to use.
   /// @param debugMode If true, infos will be printed on stderr.
-  Trainer(TransitionMachine & tm, BD & bd, Config & config, bool debugMode);
+  /// @param removeDuplicates If true, duplicates examples will be removed from the training set.
+  Trainer(TransitionMachine & tm, BD & bd, Config & config, bool debugMode, bool removeDuplicates);
   /// @brief Construct a new Trainer with a dev set.
   ///
   /// @param tm The TransitionMachine to use.
@@ -118,7 +122,8 @@ void processAllExamples(
   /// @param devBD The BD corresponding to the dev dataset.
   /// @param devConfig The Config corresponding to devBD.
   /// @param debugMode If true, infos will be printed on stderr.
-  Trainer(TransitionMachine & tm, BD & bd, Config & config, BD * devBD, Config * devConfig, bool debugMode);
+  /// @param removeDuplicates If true, duplicates examples will be removed from the training set.
+  Trainer(TransitionMachine & tm, BD & bd, Config & config, BD * devBD, Config * devConfig, bool debugMode, bool removeDuplicates);
   /// @brief Train the TransitionMachine.
   ///
   /// @param nbIter The number of training epochs.
diff --git a/trainer/src/Trainer.cpp b/trainer/src/Trainer.cpp
index ec2ce9f999d2e5b13bba57ce3e747e71548534d6..69f92f8dfa2c026a057b972b15d720395710afe1 100644
--- a/trainer/src/Trainer.cpp
+++ b/trainer/src/Trainer.cpp
@@ -1,17 +1,19 @@
 #include "Trainer.hpp"
 #include "util.hpp"
 
-Trainer::Trainer(TransitionMachine & tm, BD & bd, Config & config, bool debugMode)
+Trainer::Trainer(TransitionMachine & tm, BD & bd, Config & config, bool debugMode, bool removeDuplicates)
 : tm(tm), trainBD(bd), trainConfig(config)
 {
   this->devBD = nullptr;
   this->devConfig = nullptr;
   this->debugMode = debugMode;
+  this->removeDuplicates = removeDuplicates;
 }
 
-Trainer::Trainer(TransitionMachine & tm, BD & bd, Config & config, BD * devBD, Config * devConfig, bool debugMode) : tm(tm), trainBD(bd), trainConfig(config), devBD(devBD), devConfig(devConfig)
+Trainer::Trainer(TransitionMachine & tm, BD & bd, Config & config, BD * devBD, Config * devConfig, bool debugMode, bool removeDuplicates) : tm(tm), trainBD(bd), trainConfig(config), devBD(devBD), devConfig(devConfig)
 {
   this->debugMode = debugMode;
+  this->removeDuplicates = removeDuplicates;
 }
 
 std::map<Classifier*,TrainingExamples> Trainer::getExamplesByClassifier(Config & config)
@@ -54,6 +56,10 @@ std::map<Classifier*,TrainingExamples> Trainer::getExamplesByClassifier(Config &
     config.moveHead(transition->headMvt);
   }
 
+  if (removeDuplicates)
+    for (auto & it : examples)
+      it.second.removeDuplicates();
+
   return examples;
 }
 
diff --git a/trainer/src/macaon_train.cpp b/trainer/src/macaon_train.cpp
index ff47561aa7ea6376280254ac933482c01f03767f..2968d876ca2a2a485bb7a76ed327127a3ce20ee0 100644
--- a/trainer/src/macaon_train.cpp
+++ b/trainer/src/macaon_train.cpp
@@ -47,6 +47,8 @@ po::options_description getOptionsDescription()
       "Size of each training batch (in number of examples)")
     ("seed,s", po::value<int>()->default_value(100),
       "The random seed that will initialize RNG")
+    ("duplicates", po::value<bool>()->default_value(true),
+      "Remove identical training examples")
     ("shuffle", po::value<bool>()->default_value(true),
       "Shuffle examples after each iteration");
 
@@ -114,6 +116,7 @@ int main(int argc, char * argv[])
   int batchSize = vm["batchsize"].as<int>();
   int randomSeed = vm["seed"].as<int>();
   bool mustShuffle = vm["shuffle"].as<bool>();
+  bool removeDuplicates = vm["duplicates"].as<bool>();
   bool debugMode = vm.count("debug") == 0 ? false : true;
 
   const char * MACAON_DIR = std::getenv("MACAON_DIR");
@@ -142,14 +145,14 @@ int main(int argc, char * argv[])
 
   if(devFilename.empty())
   {
-    trainer.reset(new Trainer(tapeMachine, trainBD, trainConfig, debugMode));
+    trainer.reset(new Trainer(tapeMachine, trainBD, trainConfig, debugMode, removeDuplicates));
   }
   else
   {
     devBD.reset(new BD(BDfilename, MCDfilename));
     devConfig.reset(new Config(*devBD.get(), expPath));
     devConfig->readInput(devFilename);
-    trainer.reset(new Trainer(tapeMachine, trainBD, trainConfig, devBD.get(), devConfig.get(), debugMode));
+    trainer.reset(new Trainer(tapeMachine, trainBD, trainConfig, devBD.get(), devConfig.get(), debugMode, removeDuplicates));
   }
 
   trainer->expPath = expPath;
diff --git a/transition_machine/include/FeatureModel.hpp b/transition_machine/include/FeatureModel.hpp
index 13bd9aa9cc3056a16f73b7cd36076936ae413a1e..a7d21fc1698a7433815de06caea32b87effe5400 100644
--- a/transition_machine/include/FeatureModel.hpp
+++ b/transition_machine/include/FeatureModel.hpp
@@ -51,6 +51,11 @@ class FeatureModel
     ///
     /// @param output Where to print.
     void printForDebug(FILE * output);
+
+    /// @brief Return a string representing this FeatureDescription
+    ///
+    /// @return The string representing this FeatureDescription
+    std::string toString();
   };
 
   private :
diff --git a/transition_machine/include/TrainingExamples.hpp b/transition_machine/include/TrainingExamples.hpp
index eeb30314d2bdd3d1984ea036136899056e7a0d26..4fd52a177419eca6c80a0a951748ea305e8dfa5e 100644
--- a/transition_machine/include/TrainingExamples.hpp
+++ b/transition_machine/include/TrainingExamples.hpp
@@ -26,6 +26,8 @@ class TrainingExamples
   TrainingExamples getBatch(unsigned int batchSize);
   void reset();
   void shuffle();
+  void remove(int index);
+  void removeDuplicates();
 };
 
 #endif
diff --git a/transition_machine/src/FeatureModel.cpp b/transition_machine/src/FeatureModel.cpp
index 6f05e056962264b9696abdb906c780462ff9e172..ce272690c21b72abd1772a880438cbe4a3f3ac33 100644
--- a/transition_machine/src/FeatureModel.cpp
+++ b/transition_machine/src/FeatureModel.cpp
@@ -37,23 +37,40 @@ FeatureModel::FeatureModel(const std::string & filename)
 
 void FeatureModel::FeatureDescription::printForDebug(FILE * output)
 {
+  fprintf(output, "%s", toString().c_str());
+}
+
+std::string FeatureModel::FeatureDescription::toString()
+{
+  char buffer[1024];
+  std::string res;
+
   int nbCol = 80;
 
   for(int i = 0; i < nbCol; i++)
-    fprintf(output, "-");
-  fprintf(output, "\n");
+    res.push_back('-');
+  res.push_back('\n');
 
   for(auto featValue : values)
   {
-    fprintf(output, "Feature=%s, Policy=%s, Value=%s\n", featValue.name.c_str(), policy2str(featValue.policy), featValue.value->c_str());
+    res += "Feature=" + featValue.name;
+    res += ", Policy=" + std::string(policy2str(featValue.policy));
+    res += ", Value=" + std::string(*featValue.value);
+    res.push_back('\n');
+
     for(float val : *featValue.vec)
-      fprintf(output, "%.2f ", val);
-    fprintf(output, "\n");
+    {
+      sprintf(buffer, "%.2f ", val);
+      res += std::string(buffer);
+    }
+    res.push_back('\n');
   }
 
   for(int i = 0; i < nbCol; i++)
-    fprintf(output, "-");
-  fprintf(output, "\n");
+    res.push_back('-');
+  res.push_back('\n');
+
+  return res;
 }
 
 const char * FeatureModel::policy2str(Policy policy)
diff --git a/transition_machine/src/TrainingExamples.cpp b/transition_machine/src/TrainingExamples.cpp
index 12ac7f104e196bd9d649c51c43545af97177c1bd..a887acafb0e1222e975fdeb0a4717003790cb621 100644
--- a/transition_machine/src/TrainingExamples.cpp
+++ b/transition_machine/src/TrainingExamples.cpp
@@ -15,7 +15,7 @@ void TrainingExamples::add(const FeatureModel::FeatureDescription & example, int
 
 unsigned int TrainingExamples::size()
 {
-  return examples.size();
+  return order.size();
 }
 
 TrainingExamples TrainingExamples::getBatch(unsigned int batchSize)
@@ -41,3 +41,32 @@ void TrainingExamples::shuffle()
   std::random_shuffle(order.begin(), order.end());
 }
 
+void TrainingExamples::removeDuplicates()
+{
+  std::map<std::string, int> lastIndex;
+  std::map<int, bool> toRemove;
+
+  for (unsigned int i = 0; i < examples.size(); i++)
+  {
+    std::string example = examples[i].toString();
+
+    if (lastIndex.count(example))
+      toRemove[i] = true;
+    else
+      lastIndex[example] = i;
+  }
+
+  for (auto & it : toRemove)
+    remove(it.first);
+}
+
+void TrainingExamples::remove(int index)
+{
+  for (unsigned int i = 0; i < order.size(); i++)
+    if ((int)order[i] == index)
+    {
+      order[i] = order.back();
+      order.pop_back();
+    }
+}
+