Method reserve

include/Eigen/Eigen/src/SparseCore/SparseMatrix.h:300–304

Preallocates \a reserveSize non zeros. * * Precondition: the matrix must be in compressed mode. */

      *
      * Precondition: the matrix must be in compressed mode. */
    inline void reserve(Index reserveSize)
    {
      eigen_assert(isCompressed() && "This function does not make sense in non compressed mode.");
      m_data.reserve(reserveSize);
    }
    
    #ifdef EIGEN_PARSED_BY_DOXYGEN
    /** Preallocates \a reserveSize[\c j] non zeros for each column (resp. row) \c j.