human: Given a node-centered hypergraph: <hypergraph>, where nodes represent papers and hyperedges represent sets of papers co-cited by a source paper.

Details of the hypergraph:
Center node: "a parallel sweeping preconditioner for heterogeneous 3d helmholtz equations"
  Abstract: A parallelization of a sweeping preconditioner for three-dimensional Helmholtz equations without large cavities is introduced and benchmarked for several challenging velocity models. The setup and application costs of the sequential preconditioner are shown to be $O(\gamma^2 N^{4/3})$ and $O(\gamma N \log N)$, where $\gamma(\omega)$ denotes the modestly frequency-dependent number of grid points per perfectly matched layer. Several computational and memory improvements are introduced relative to using black-box sparse-direct solvers for the auxiliary problems, and competitive runtimes and iteration counts are reported for high-frequency problems distributed over thousands of cores. Two open-source packages are released along with this paper: Parallel Sweeping Preconditioner (PSP) and the underlying distributed multifrontal solver, Clique.

Connected through hyperedge HE-1 (induced by source paper "a multigrid solver to the helmholtz equation with a point source based on travel time and amplitude"):
  with members:
    - "complex additive geometric multilevel solvers for helmholtz equations on spacetrees"
    - "full waveform inversion guided by travel time tomography"
    - "jinv a flexible julia package for pde parameter estimation"
    - "a fast marching algorithm for the factored eikonal equation"
    - "julia a fresh approach to numerical computing"

Connected through hyperedge HE-2 (induced by source paper "a unified 2d 3d large scale software environment for nonlinear inverse problems"):
  with members:
    - "julia a fresh approach to numerical computing"
    - "automated derivation of the adjoint of high level transient finite element programs"
    - "robust inversion dimensionality reduction and randomized sampling"

Connected through hyperedge HE-3 (induced by source paper "full waveform inversion guided by travel time tomography"):
  with members:
    - "complex additive geometric multilevel solvers for helmholtz equations on spacetrees"
    - "a fast marching algorithm for the factored eikonal equation"

Question: Please tell me which class the center node belongs to. The 40 classes are: cs.NA(Numerical Analysis), cs.MM(Multimedia), cs.LO(Logic in Computer Science), cs.CY(Computers and Society), cs.CR(Cryptography and Security), cs.DC(Distributed, Parallel, and Cluster Computing), cs.HC(Human-Computer Interaction), cs.CE(Computational Engineering, Finance, and Science), cs.NI(Networking and Internet Architecture), cs.CC(Computational Complexity), cs.AI(Artificial Intelligence), cs.MA(Multiagent Systems), cs.GL(General Literature), cs.NE(Neural and Evolutionary Computing), cs.SC(Symbolic Computation), cs.AR(Hardware Architecture), cs.CV(Computer Vision and Pattern Recognition), cs.GR(Graphics), cs.ET(Emerging Technologies), cs.SY(Systems and Control), cs.CG(Computational Geometry), cs.OH(Other Computer Science), cs.PL(Programming Languages), cs.SE(Software Engineering), cs.LG(Machine Learning), cs.SD(Sound), cs.SI(Social and Information Networks), cs.RO(Robotics), cs.IT(Information Theory), cs.PF(Performance), cs.CL(Computation and Language), cs.IR(Information Retrieval), cs.MS(Mathematical Software), cs.FL(Formal Languages and Automata Theory), cs.DS(Data Structures and Algorithms), cs.OS(Operating Systems), cs.GT(Computer Science and Game Theory), cs.DB(Databases), cs.DL(Digital Libraries), cs.DM(Discrete Mathematics). Directly output the class name.

gpt: cs.NA(Numerical Analysis)