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: "optimal sorting networks"
  Abstract: This paper settles the optimality of sorting networks given in The Art of Computer Programming vol. 3 more than 40 years ago. The book lists efficient sorting networks with n <= 16 inputs. In this paper we give general combinatorial arguments showing that if a sorting network with a given depth exists then there exists one with a special form. We then construct propositional formulas whose satisfiability is necessary for the existence of such a network. Using a SAT solver we conclude that the listed networks have optimal depth. For n <= 10 inputs where optimality was known previously, our algorithm is four orders of magnitude faster than those in prior work.

Connected through hyperedge HE-1 (induced by source paper "optimal metastability containing sorting via parallel prefix computation"):
  with members:
    - "optimal metastability containing sorting networks"
    - "on the complexity of hazard free circuits"
    - "metastability containing circuits"
    - "self stabilizing byzantine clock synchronization with optimal precision"

Connected through hyperedge HE-2 (induced by source paper "joint size and depth optimization of sorting networks"):
  with members:
    - "sorting networks to the end and back again"
    - "new bounds on optimal sorting networks"

Connected through hyperedge HE-3 (induced by source paper "optimal depth sorting networks"):
  with members:
    - "sorting networks to the end and back again"
    - "solving and verifying the boolean pythagorean triples problem via cube and conquer"
    - "new bounds on optimal sorting networks"
    - "computing the ramsey number r 4 3 3 using abstraction and symmetry breaking"
    - "applying sorting networks to synthesize optimized sorting libraries"
    - "sorting networks the end game"
    - "the quest for optimal sorting networks efficient generation of two layer prefixes"
    - "twenty five comparators is optimal when sorting nine inputs and twenty nine for ten"

Connected through hyperedge HE-4 (induced by source paper "an improved subsumption testing algorithm for the optimal size sorting network problem"):
  with members:
    - "sorting networks to the end and back again"
    - "new bounds on optimal sorting networks"
    - "the quest for optimal sorting networks efficient generation of two layer prefixes"
    - "twenty five comparators is optimal when sorting nine inputs and twenty nine for ten"

Connected through hyperedge HE-5 (induced by source paper "sorting networks to the end and back again"):
  with members:
    - "optimal depth sorting networks"
    - "new bounds on optimal sorting networks"
    - "applying sorting networks to synthesize optimized sorting libraries"
    - "sorting networks the end game"
    - "the quest for optimal sorting networks efficient generation of two layer prefixes"

Connected through hyperedge HE-6 (induced by source paper "applying sorting networks to synthesize optimized sorting libraries"):
  with members:
    - "new bounds on optimal sorting networks"
    - "sorting networks the end game"
    - "the quest for optimal sorting networks efficient generation of two layer prefixes"
    - "twenty five comparators is optimal when sorting nine inputs and twenty nine for ten"

Connected through hyperedge HE-7 (induced by source paper "sorting networks the end game"):
  with members:
    - "the quest for optimal sorting networks efficient generation of two layer prefixes"
    - "faster sorting networks for 17 19 and 20 inputs"
    - "twenty five comparators is optimal when sorting nine inputs and twenty nine for ten"

Connected through hyperedge HE-8 (induced by source paper "new bounds on optimal sorting networks"):
  with members:
    - "sorting networks the end game"
    - "the quest for optimal sorting networks efficient generation of two layer prefixes"

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.DM(Discrete Mathematics)