-> pas d'info sur la position... (si ce n'est peanokey StartKey)
TopNodes[no].Daughter == -1
--> pas cde cellules filles
struct topnode_data
{
int Daughter; /*!< index of first daughter cell (out of 8) of top-level node */
int Pstart; /*!< for the present top-level node, this gives the index of the first node in the concatenated list of topnodes collected from all processors */
int Blocks; /*!< for the present top-level node, this gives the number of corresponding nodes in the concatenated list of topnodes collected from all processors */
int Leaf; /*!< if the node is a leaf, this gives its number when all leaves are traversed in Peano-Hilbert order */
peanokey Size; /*!< number of Peano-Hilbert mesh-cells represented by top-level node */
peanokey StartKey; /*!< first Peano-Hilbert key in top-level node */
long long Count; /*!< counts the number of particles in this top-level node */