diff --git a/Addons/CKernelApi/Src/CScalfmmApi.h b/Addons/CKernelApi/Src/CScalfmmApi.h
index 29269af8bc224be36424547034a1f40432210cb9..92b033ed4ddecfb7d3612e45e0912fd2ffcb902c 100644
--- a/Addons/CKernelApi/Src/CScalfmmApi.h
+++ b/Addons/CKernelApi/Src/CScalfmmApi.h
@@ -170,7 +170,7 @@ typedef void (*Callback_copy_cell)(void * userDatas, FSize size, void * memoryAl
  * @param userData cell user data
  * @param userData Kernel user data
  */
-typedef void (*Callback_finalize_leaf)(int level, FSize nbParts, const FSize * idxParts, long long morton_index, double center[3],
+typedef void (*Callback_apply_on_leaf)(int level, FSize nbParts, const FSize * idxParts, long long morton_index, double center[3],
                                        void * cellDatas,void * leafDatas, void * userDatas);
 
 /**
@@ -608,7 +608,7 @@ typedef void (*Callback_P2PSym)(void * targetLeaf, FSize nbParticles, const FSiz
  * @param spatial_position double[3] center of the cell
  * @param usercell ptr to user's cell
  */
-typedef void (*Callback_reset_cell)(int level, long long morton_index, int* tree_position, double* spatial_position, void * userCell, void * userData);
+typedef void (*Callback_apply_on_cell)(int level, long long morton_index, int* tree_position, double* spatial_position, void * userCell, void * userData);
 
 /**
  * @brief Structure containing callbacks to fill in order to define
@@ -667,7 +667,7 @@ void scalfmm_execute_fmm(scalfmm_handle Handle);
  * called after insert_parts.
  * @param
  */
-void scalfmm_apply_on_leaf(scalfmm_handle Handle, Callback_finalize_leaf function);
+void scalfmm_apply_on_leaf(scalfmm_handle Handle, Callback_apply_on_leaf function);
 
 
 /////////////////////////////////////////////////////////////////////
@@ -689,11 +689,10 @@ void scalfmm_apply_on_leaf(scalfmm_handle Handle, Callback_finalize_leaf functio
 void scalfmm_dealloc_handle(scalfmm_handle handle, Callback_free_cell cellDestroyer);
 
 /**
- * @brief this function reset all the data of the tree. (i e multipole
- * and local development, forces and potentials)
+ * @brief This function apply the function param on each cell of the octree
  * @param Handle scalfmm_handle provided by scalfmm_init.
  */
-void scalfmm_reset_tree(scalfmm_handle handle, Callback_reset_cell cellReseter);
+void scalfmm_apply_on_cell(scalfmm_handle handle, Callback_apply_on_cell function);
 
 /////////////////////////////////////////////////////////////////////
 ///////////////       Monitoring functions          /////////////////
diff --git a/Addons/CKernelApi/Src/FInterEngine.hpp b/Addons/CKernelApi/Src/FInterEngine.hpp
index d2165dbf17792c19e03401acdb9beb1a6277caf3..499e74e1a6fb4942799b36ccc58fd7574c601d95 100644
--- a/Addons/CKernelApi/Src/FInterEngine.hpp
+++ b/Addons/CKernelApi/Src/FInterEngine.hpp
@@ -716,8 +716,9 @@ public:
     }
 
     //Simple call to FScalFMMEngine method with good template
-    void reset_tree(Callback_reset_cell /*not used*/){
-        FScalFMMEngine<FReal>::template generic_reset_tree<ContainerClass,InterCell,LeafClass>(octree);
+    void apply_on_cell(Callback_apply_on_cell /*not used*/){
+        //We used this one to clean the Cehb cell in the user defined cheb kernel situation.
+        FScalFMMEngine<FReal>::template generic_apply_on_cell<ContainerClass,InterCell,LeafClass>(octree);
     }
 
 
diff --git a/Addons/CKernelApi/Src/FScalFMMEngine.hpp b/Addons/CKernelApi/Src/FScalFMMEngine.hpp
index 2f1e97c20db8d119380508167a7832bb5b4c8e0e..a397fb7dfebc00b758f150a96ce1f3b20cc132fe 100644
--- a/Addons/CKernelApi/Src/FScalFMMEngine.hpp
+++ b/Addons/CKernelApi/Src/FScalFMMEngine.hpp
@@ -173,7 +173,7 @@ public:
     virtual void set_potentials_npart( int nbParts, int* idxOfParticles, FReal * potentialsToRead, PartType type){
         FAssertLF(0,"No tree instancied, exiting ...\n");
     }
-    virtual void apply_on_each_leaf(Callback_finalize_leaf function){
+    virtual void apply_on_each_leaf(Callback_apply_on_leaf function){
         FAssertLF(0,"No tree instancied, exiting ...\n");
     }
 
@@ -771,11 +771,11 @@ public:
         }
     }
 
-    virtual void reset_tree(Callback_reset_cell cellReset){
+    virtual void apply_on_cell(Callback_apply_on_cell function){
     }
 
     template<class ContainerClass, class CellClass, class LeafClass>
-    void generic_reset_tree(FOctree<FReal,CellClass,ContainerClass,LeafClass> * tree){
+    void generic_apply_on_cell(FOctree<FReal,CellClass,ContainerClass,LeafClass> * tree){
         //Reset forces and potentials
         tree->forEachLeaf([&](LeafClass * leaf){
                 ContainerClass * targets = leaf->getTargets();
@@ -1057,8 +1057,8 @@ extern "C" void scalfmm_utils_interactionPosition(int interactionPosition, int*
 }
 
 
-extern "C" void scalfmm_reset_tree(scalfmm_handle Handle, Callback_reset_cell cellReseter){
-    ((ScalFmmCoreHandle<double> * ) Handle)->engine->reset_tree(cellReseter);
+extern "C" void scalfmm_apply_on_cell(scalfmm_handle Handle, Callback_apply_on_cell function){
+    ((ScalFmmCoreHandle<double> * ) Handle)->engine->apply_on_cell(function);
 }
 
 extern "C" void scalfmm_print_everything(scalfmm_handle Handle){
@@ -1069,7 +1069,7 @@ extern "C" void scalfmm_set_upper_limit(scalfmm_handle Handle, int upperLimit){
     ((ScalFmmCoreHandle<double> * ) Handle)->engine->set_upper_limit(upperLimit);
 }
 
-extern "C" void scalfmm_apply_on_leaf(scalfmm_handle Handle, Callback_finalize_leaf function){
+extern "C" void scalfmm_apply_on_leaf(scalfmm_handle Handle, Callback_apply_on_leaf function){
     ((ScalFmmCoreHandle<double> * ) Handle)->engine->apply_on_each_leaf(function);
 }
 
diff --git a/Addons/CKernelApi/Src/FScalfmmApiInit.cpp b/Addons/CKernelApi/Src/FScalfmmApiInit.cpp
index b1fb350e74f860fb2d552e3cca1c952cd75d94fd..556467a0ad02a0471823022a0250fb6a44073d7a 100644
--- a/Addons/CKernelApi/Src/FScalfmmApiInit.cpp
+++ b/Addons/CKernelApi/Src/FScalfmmApiInit.cpp
@@ -386,7 +386,7 @@ void ChebKernel_P2P(FSize nbParticles, const FSize* particleIndexes, const FSize
     //Empty tree coordinate
     int coord[3] = {0,0,0};
 
-    inKernelStruct->kernel[id_thread]->P2P(FTreeCoordinate(coord),tempContTarget,nullptr,tempContSources,sourcePosition,size);
+    inKernelStruct->kernel[id_thread]->P2P(FTreeCoordinate(coord),tempContTarget,tempContTarget,tempContSources,sourcePosition,size);
 
     //get back forces & potentials
     double * forcesToFill = reinterpret_cast<UserData *>(inKernel)->forcesComputed[id_thread];
diff --git a/Addons/CKernelApi/Src/FUserKernelDistrEngine.hpp b/Addons/CKernelApi/Src/FUserKernelDistrEngine.hpp
index 7f6fbd153da7a2666fac6794fb8c3c78beed6f01..dba12ace23184eb84ebf61a35dea3d788b5049a0 100644
--- a/Addons/CKernelApi/Src/FUserKernelDistrEngine.hpp
+++ b/Addons/CKernelApi/Src/FUserKernelDistrEngine.hpp
@@ -637,7 +637,7 @@ public:
             });
     }
 
-    void apply_on_each_leaf(Callback_finalize_leaf function){
+    void apply_on_each_leaf(Callback_apply_on_leaf function){
         if(octreeDist){
             FUserKernelEngine<FReal,LeafClass>::template generic_apply_on_each_leaf<ContainerClass,CoreCellDist>(octreeDist,kernel->getUserKernelDatas(),function);
         }else{
diff --git a/Addons/CKernelApi/Src/FUserKernelEngine.hpp b/Addons/CKernelApi/Src/FUserKernelEngine.hpp
index 2f7d6bf8b40cda3d6c10209c79244dd197da84d6..9b267b4bca7198c344f206beb1e3f20614b57144 100644
--- a/Addons/CKernelApi/Src/FUserKernelEngine.hpp
+++ b/Addons/CKernelApi/Src/FUserKernelEngine.hpp
@@ -335,7 +335,7 @@ public:
         this->octree = new OctreeClass(TreeHeight,FMath::Min(3,TreeHeight-1),BoxWidth,FPoint<FReal>(BoxCenter));
     }
 
-    void reset_tree(Callback_reset_cell cellReset){
+    void apply_on_cell(Callback_apply_on_cell function){
         double boxwidth = octree->getBoxWidth();
         //apply user function reset on each user's cell
         octree->forEachCellWithLevel([&](CoreCell * currCell,const int currLevel){
@@ -347,7 +347,7 @@ public:
                     position[0] = boxCorner.getX() + currCoord.getX()*boxwidth/double(1<<currLevel);
                     position[1] = boxCorner.getY() + currCoord.getY()*boxwidth/double(1<<currLevel);
                     position[2] = boxCorner.getZ() + currCoord.getZ()*boxwidth/double(1<<currLevel);
-                    cellReset(currLevel,currMorton,arrayCoord,position,currCell->getContainer(),kernel->getUserKernelDatas());
+                    function(currLevel,currMorton,arrayCoord,position,currCell->getContainer(),kernel->getUserKernelDatas());
                 }
             });
     }
@@ -444,14 +444,14 @@ public:
         FScalFMMEngine<FReal>::template generic_set_positions_npart<ContainerClass,LeafClass,CoreCell>(octree,NbPositions,idxOfParticles,X,Y,Z,type);
     }
 
-    virtual void apply_on_each_leaf(Callback_finalize_leaf function){
+    virtual void apply_on_each_leaf(Callback_apply_on_leaf function){
         generic_apply_on_each_leaf<ContainerClass,CoreCell>(octree,kernel->getUserKernelDatas(),function);
     }
 
     template<class ContainerClass,class CellClass>
     void generic_apply_on_each_leaf(FOctree<FReal,CellClass,ContainerClass,LeafClass>* octreeIn,
                                     void * kernelUserData,
-                                    Callback_finalize_leaf function){
+                                    Callback_apply_on_leaf function){
         if(octreeIn){
             octreeIn->forEachCellLeaf([&](CoreCell * currCell, LeafClass * leaf){
                     int lvl = octreeIn->getHeight();
diff --git a/Addons/CKernelApi/Tests/testChebInterface.c b/Addons/CKernelApi/Tests/testChebInterface.c
index 0d59b21f946b31c39263aaf9e525191cdad48053..5c0cda316128d91493826c80f1f9b0413649ff87 100644
--- a/Addons/CKernelApi/Tests/testChebInterface.c
+++ b/Addons/CKernelApi/Tests/testChebInterface.c
@@ -99,13 +99,13 @@ void on_leaf(int level, FSize nbParts, const FSize * idxParts, long long morton_
  * @param number of particle (no default value)
  */
 int main(int argc, char ** av){
-    omp_set_num_threads(1);
+    //omp_set_num_threads(1);
     printf("Start\n");
     if(argc<2){
         printf("Use : %s nb_part (optionnal : TreeHeight) \nexiting\n",av[0]);
         exit(0);
     }
-    int nbPart= atoi(av[1]);
+    int nbPart= atoi(av[1]);;
     int treeHeight = 5 ;
     if(argc>2){
         int treeHeight = atoi(av[2]);
@@ -125,12 +125,9 @@ int main(int argc, char ** av){
         printf("Creating Particles:\n");
         FSize idxPart;
         for(idxPart = 0 ; idxPart < nbPart ; ++idxPart){
-            particleXYZ[idxPart*3]   = (random()/(double)(RAND_MAX))*boxWidth
-                - boxWidth/2 + boxCenter[0];
-            particleXYZ[idxPart*3+1] = (random()/(double)(RAND_MAX))*boxWidth
-                - boxWidth/2 + boxCenter[1];
-            particleXYZ[idxPart*3+2] = (random()/(double)(RAND_MAX))*boxWidth
-                - boxWidth/2 + boxCenter[2];
+            particleXYZ[idxPart*3]   = (random()/(double)(RAND_MAX))*boxWidth - boxWidth/2 + boxCenter[0];
+            particleXYZ[idxPart*3+1] = (random()/(double)(RAND_MAX))*boxWidth - boxWidth/2 + boxCenter[1];
+            particleXYZ[idxPart*3+2] = (random()/(double)(RAND_MAX))*boxWidth - boxWidth/2 + boxCenter[2];
             physicalValues[idxPart] = 1.0;
         }
     }
@@ -360,8 +357,8 @@ int main(int argc, char ** av){
         free(potentialsRef);
 
         //Reset
-        scalfmm_reset_tree(handle,cheb_resetCell);
-        scalfmm_reset_tree(handle_ref,NULL);
+        scalfmm_apply_on_cell(handle,cheb_resetCell);
+        scalfmm_apply_on_cell(handle_ref,NULL);
 
         printf("Internal resets done \n");