Eigen3 OpenMP Declaraction

example.hpp

  #pragma omp declare reduction( \
                  +: \
                  Matrix6d: \
                  omp_out= omp_out + omp_in) \
                  initializer(omp_priv=Matrix6d::Zero())
  #pragma omp declare reduction( \
                  +: \
                  Vector6d: \
                  omp_out = omp_out + omp_in) \
                  initializer(omp_priv=Vector6d::Zero())
  #pragma omp parallel for reduction(+: ATA) \
                           reduction(+: ATb)