static void algo(const se3::JointModelBase<JointModel> & jmodel,
		     se3::JointDataBase<typename JointModel::JointData> & jdata,
		     const se3::Model& model,
		     se3::Data& data,
		     const bool & computeSubtreeComs )
    {
      using namespace Eigen;
      using namespace se3;

      const Model::Index & i      = jmodel.id();
      const Model::Index & parent = model.parents[i];

      data.com[parent]  += data.com[i];
      data.mass[parent] += data.mass[i];

      const Eigen::Matrix<double,6,JointModel::NV> & oSk
	= data.oMi[i].act(jdata.S());

      if( JointModel::NV==1 )
      	data.Jcom.col(jmodel.idx_v()) // Using head and tail would confuse g++
      	  = data.mass[i]*oSk.template topLeftCorner<3,1>() 
      	  - data.com[i].cross(oSk.template bottomLeftCorner<3,1>()) ;
      else
      	data.Jcom.template block<3,JointModel::NV>(0,jmodel.idx_v())
      	  = data.mass[i]*oSk.template topRows<3>() 
      	  - skew(data.com[i]) * oSk.template bottomRows<3>() ;

      if(computeSubtreeComs)
	data.com[i]       /= data.mass[i];
    }
    static void algo(const se3::JointModelBase<JointModel> & jmodel,
		     se3::JointDataBase<typename JointModel::JointData> & jdata,
		     const se3::Model& model,
		     se3::Data& data,
		     const Eigen::VectorXd & q)
    {
      using namespace Eigen;
      using namespace se3;

      const Model::Index & i      = jmodel.id();
      const Model::Index & parent = model.parents[i];

      jmodel.calc(jdata.derived(),q);
      
      data.liMi[i]      = model.jointPlacements[i]*jdata.M();
      if(parent>0) data.oMi[i] = data.oMi[parent]*data.liMi[i];
      else         data.oMi[i] = data.liMi[i];
      
      data.com[i]   = model.inertias[i].mass()*data.oMi[i].act(model.inertias[i].lever());
      data.mass[i]  = model.inertias[i].mass();
    }
    static void algo(const se3::JointModelBase<JointModel> & jmodel,
		     se3::JointDataBase<typename JointModel::JointData> & jdata,
		     const se3::Model& model,
		     se3::Data& data,
		     const Eigen::VectorXd & q,
		     const bool & computeSubtreeComs)
    {
      using namespace Eigen;
      using namespace se3;

      const std::size_t & i      = jmodel.id();
      const std::size_t & parent = model.parents[i];

      jmodel.calc(jdata.derived(),q);
      
      data.liMi[i]      = model.jointPlacements[i]*jdata.M();
      data.com[parent]  += (data.liMi[i].rotation()*data.com[i]
			    +data.mass[i]*data.liMi[i].translation());
      data.mass[parent] += data.mass[i];  

      if( computeSubtreeComs )
	data.com[i] /= data.mass[i]; 
    }