diff --git a/MakefileNoOTB b/MakefileNoOTB
index 26a0ea9..d9c16f7 100644
--- a/MakefileNoOTB
+++ b/MakefileNoOTB
@@ -16,11 +16,15 @@ TST_PRG = TestArrayTreeBuilder
 TST_SRC = $(patsubst %, $(CPP_DIR)/%.cpp, $(TST_PRG))
 TST_OUT = $(patsubst %, $(OUT_DIR)/%, $(TST_PRG))
 
+PRF_PRG = PerfArrayTreeBuilder
+PRF_SRC = $(patsubst %, $(CPP_DIR)/%.cpp, $(PRF_PRG))
+PRF_OUT = $(patsubst %, $(OUT_DIR)/%, $(PRF_PRG))
+
 ## FLAGS ###############################
 DFLAGS = -O2 -DNDEBUG -DBOOST_DISABLE_ASSERTS -DNO_OTB -DINTEL_TBB_THREAD
 #DFLAGS = -g -DENABLE_LOG -DNO_OTB -DTHREAD_DISABLE -DENABLE_SMART_LOG
 IFLAGS = $(DFLAGS) -MMD -I$(HPP_DIR)
-LFLAGS = -L$(LIB_DIR) -ltriskele -lstdc++ -lpthread -ltbb -lboost_system -lboost_chrono -lboost_thread -lboost_program_options -lboost_date_time -lboost_serialization -lboost_filesystem -lboost_unit_test_framework -lgdal
+LFLAGS = -L$(LIB_DIR) -ltriskele -lstdc++ -lpthread -lboost_system -lboost_chrono -lboost_thread -lboost_program_options -lboost_date_time -lboost_serialization -lboost_filesystem -lboost_unit_test_framework -lgdal -ltbb
 CC = g++
 
 ## RULES ###############################
@@ -35,15 +39,16 @@ $(OUT_DIR)/%: $(CPP_DIR)/*/%.cpp
 	$(CC) $(IFLAGS) $< -L$(LIB_DIR) $(LFLAGS) -cpp -o $@
 
 ## ENTRIES #############################
-all:	init libtriskele apGenerator test
+all:	init libtriskele apGenerator test pref
 
 testA: all
 	$(TST_OUT)
 
 testB: all
-#	$(APG_OUT) data/nairobi-byte.tif data/result.tif -b 0 -w 4000 -h 4000 --min-tree -A data/areaThresholds.txt #  --debug
-#	$(APG_OUT) data/10m.tif data/result.tif -b 0 --min-tree --max-tree --tos-tree -A data/areaThresholds.txt -S data/sdThresholds.txt -M data/moiThresholds.txt #  --debug
-	$(APG_OUT) data/10m.tif data/result.tif --min-tree --max-tree --tos-tree -A data/areaThresholds.txt -S data/sdThresholds.txt -M data/moiThresholds.txt #  --debug
+	$(APG_OUT) data/10m.tif data/result.tif --min-tree --max-tree --tos-tree --alpha-tree -A data/areaThresholds.txt -S data/sdThresholds.txt -M data/moiThresholds.txt #  --debug
+
+perfA: all
+	$(PRF_OUT) MIN 8 20 1000000
 
 init:
 	mkdir -p $(OUT_DIR) $(OBJ_DIR) $(LIB_DIR)
@@ -58,10 +63,12 @@ wipe: clean
 libtriskele: $(LIB_DIR)/libtriskele.a
 
 $(APG_OUT): $(APG_SRC) $(LIB_DIR)/libtriskele.a
-apGenerator: $(APG_OUT)
-
 $(TST_OUT): $(TST_SRC) $(LIB_DIR)/libtriskele.a
-test: $(TST_OUT)
+$(PRF_OUT): $(PRF_SRC) $(LIB_DIR)/libtriskele.a
+
+apGenerator: $(APG_OUT)
+test: init $(TST_OUT)
+pref: init $(PRF_OUT)
 
 
 ## DEPENDS #############################
diff --git a/include/ArrayTree/ArrayTreeBuilder.hpp b/include/ArrayTree/ArrayTreeBuilder.hpp
index 7e31d2b..290f600 100644
--- a/include/ArrayTree/ArrayTreeBuilder.hpp
+++ b/include/ArrayTree/ArrayTreeBuilder.hpp
@@ -38,7 +38,7 @@ namespace otb {
 	DimImg			*newCompId;
 	WeightT			*compWeights;
       public:
-	inline ArrayTreeBuilder (Raster<PixelT> &raster, const GraphWalker &graphWalker,
+	inline ArrayTreeBuilder (const Raster<PixelT> &raster, const GraphWalker &graphWalker,
 				 const TreeType &treeType, const bool &countingSort = true);
 	inline ~ArrayTreeBuilder ();
 
diff --git a/include/ArrayTree/ArrayTreeBuilder.tpp b/include/ArrayTree/ArrayTreeBuilder.tpp
index dacc8fc..b514837 100644
--- a/include/ArrayTree/ArrayTreeBuilder.tpp
+++ b/include/ArrayTree/ArrayTreeBuilder.tpp
@@ -6,7 +6,7 @@ using namespace boost::chrono;
 // ========================================
 template<typename WeightT, typename PixelT>
 inline
-ArrayTreeBuilder<WeightT, PixelT>::ArrayTreeBuilder (Raster<PixelT> &raster, const GraphWalker &graphWalker,
+ArrayTreeBuilder<WeightT, PixelT>::ArrayTreeBuilder (const Raster<PixelT> &raster, const GraphWalker &graphWalker,
 						     const TreeType &treeType, const bool &countingSort) :
   coreCount (boost::thread::hardware_concurrency ()),
   raster (raster),
diff --git a/include/TreeStats.hpp b/include/TreeStats.hpp
index 4347b10..d981ad2 100644
--- a/include/TreeStats.hpp
+++ b/include/TreeStats.hpp
@@ -47,9 +47,10 @@ namespace otb {
 
     class TreeStats {
     public :
-      //void reset ();
+      void reset ();
       inline void addDim (const TreeType &treeType, const DimImg& leafCount, const DimImg& compCount);
       inline void addTime (const TimeType &timeType, const double &duration);
+      inline const TreeStatsDouble &getTimeStats (const TimeType &timeType);
 
       // nice ostream
       struct CPrintDim {
@@ -68,6 +69,7 @@ namespace otb {
       };
       CPrintTime printTime () const;
       friend ostream &operator << (ostream& out, const CPrintTime &cpt) { return cpt.print (out); }
+
     private :
 
       TreeStatsDim leavesStats[TreeTypeCard], compStats[TreeTypeCard];
diff --git a/include/TreeStats.tpp b/include/TreeStats.tpp
index dbd7ac5..b57edae 100644
--- a/include/TreeStats.tpp
+++ b/include/TreeStats.tpp
@@ -13,6 +13,11 @@ TreeStats::addTime (const TimeType &timeType, const double &duration) {
   timeStats[timeType] (duration);
 }
 
+inline const TreeStatsDouble &
+TreeStats::getTimeStats (const TimeType &timeType) {
+  return timeStats [timeType];
+}
+
 // ========================================
 
 
diff --git a/src/TreeStats.cpp b/src/TreeStats.cpp
index c9d1ef7..24aeda8 100644
--- a/src/TreeStats.cpp
+++ b/src/TreeStats.cpp
@@ -24,6 +24,17 @@ static string timeTypeLabels [TimeTypeCard] = {
 
 TreeStats globalTreeStats;
 
+// ========================================
+void
+TreeStats::reset () {
+  for (unsigned int i = 0; i < TreeTypeCard; ++i) {
+    leavesStats[i] = TreeStatsDim ();
+    compStats[i] = TreeStatsDim ();
+  }
+  for (unsigned int i = 0; i < TimeTypeCard; ++i)
+    timeStats[i] = TreeStatsDouble ();
+}
+
 // ========================================
 using namespace boost::chrono;
 inline string