/usr/include/gmm/ is in libgmm++-dev 5.2+dfsg1-6.
This file is owned by root:root, with mode 0o755.
..
/usr/include/gmm/getfem_arch_config.h
/usr/include/gmm/gmm.h
/usr/include/gmm/gmm_MUMPS_interface.h
/usr/include/gmm/gmm_algobase.h
/usr/include/gmm/gmm_blas.h
/usr/include/gmm/gmm_blas_interface.h
/usr/include/gmm/gmm_condition_number.h
/usr/include/gmm/gmm_conjugated.h
/usr/include/gmm/gmm_def.h
/usr/include/gmm/gmm_dense_Householder.h
/usr/include/gmm/gmm_dense_lu.h
/usr/include/gmm/gmm_dense_matrix_functions.h
/usr/include/gmm/gmm_dense_qr.h
/usr/include/gmm/gmm_dense_sylvester.h
/usr/include/gmm/gmm_domain_decomp.h
/usr/include/gmm/gmm_except.h
/usr/include/gmm/gmm_inoutput.h
/usr/include/gmm/gmm_interface.h
/usr/include/gmm/gmm_interface_bgeot.h
/usr/include/gmm/gmm_iter.h
/usr/include/gmm/gmm_iter_solvers.h
/usr/include/gmm/gmm_kernel.h
/usr/include/gmm/gmm_lapack_interface.h
/usr/include/gmm/gmm_least_squares_cg.h
/usr/include/gmm/gmm_matrix.h
/usr/include/gmm/gmm_modified_gram_schmidt.h
/usr/include/gmm/gmm_opt.h
/usr/include/gmm/gmm_precond.h
/usr/include/gmm/gmm_precond_diagonal.h
/usr/include/gmm/gmm_precond_ildlt.h
/usr/include/gmm/gmm_precond_ildltt.h
/usr/include/gmm/gmm_precond_ilu.h
/usr/include/gmm/gmm_precond_ilut.h
/usr/include/gmm/gmm_precond_ilutp.h
/usr/include/gmm/gmm_precond_mr_approx_inverse.h
/usr/include/gmm/gmm_range_basis.h
/usr/include/gmm/gmm_real_part.h
/usr/include/gmm/gmm_ref.h
/usr/include/gmm/gmm_scaled.h
/usr/include/gmm/gmm_solver_Schwarz_additive.h
/usr/include/gmm/gmm_solver_bfgs.h
/usr/include/gmm/gmm_solver_bicgstab.h
/usr/include/gmm/gmm_solver_cg.h
/usr/include/gmm/gmm_solver_constrained_cg.h
/usr/include/gmm/gmm_solver_gmres.h
/usr/include/gmm/gmm_solver_idgmres.h
/usr/include/gmm/gmm_solver_qmr.h
/usr/include/gmm/gmm_std.h
/usr/include/gmm/gmm_sub_index.h
/usr/include/gmm/gmm_sub_matrix.h
/usr/include/gmm/gmm_sub_vector.h
/usr/include/gmm/gmm_superlu_interface.h
/usr/include/gmm/gmm_transposed.h
/usr/include/gmm/gmm_tri_solve.h
/usr/include/gmm/gmm_vector.h
/usr/include/gmm/gmm_vector_to_matrix.h