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: "an empirical study of speculative concurrency in ethereum smart contracts"
  Abstract: We use historical data to estimate the potential benefit of speculative techniques for executing Ethereum smart contracts in parallel. We replay transaction traces of sampled blocks from the Ethereum blockchain over time, using a simple speculative execution engine. In this engine, miners attempt to execute all transactions in a block in parallel, rolling back those that cause data conflicts. Aborted transactions are then executed sequentially. Validators execute the same schedule as miners. #R##N#We find that our speculative technique yields estimated speed-ups starting at about 8-fold in 2016, declining to about 2-fold at the end of 2017, where speed-up is measured using either gas costs or instruction counts. We also observe that a small set of contracts are responsible for many data conflicts resulting from speculative concurrent execution.

Connected through hyperedge HE-1 (induced by source paper "on exploiting transaction concurrency to speed up blockchains"):
  with members:
    - "blockchains and distributed databases a twin study"
    - "the security reference architecture for blockchains towards a standardized model for studying vulnerabilities threats and defenses"
    - "hotstuff bft consensus in the lens of blockchain"
    - "a concurrent perspective on smart contracts"
    - "adding concurrency to smart contracts"
    - "blockbench a framework for analyzing private blockchains"
    - "untangling blockchain a data processing view of blockchain systems"

Connected through hyperedge HE-2 (induced by source paper "dipetrans a framework for distributed parallel execution of transactions of blocks in blockchain"):
  with members:
    - "achieving greater concurrency in execution of smart contracts using object semantics"
    - "security and privacy on blockchain"
    - "a true concurrent model of smart contracts executions"
    - "an efficient framework for optimistic concurrent execution of smart contracts"
    - "chainspace a sharded smart contracts platform"
    - "adding concurrency to smart contracts"
    - "the miner s dilemma"
    - "majority is not enough bitcoin mining is vulnerable"

Connected through hyperedge HE-3 (induced by source paper "empirically analyzing ethereum s gas mechanism"):
  with members:
    - "decentralization in bitcoin and ethereum networks"
    - "an efficient framework for optimistic concurrent execution of smart contracts"
    - "chainspace a sharded smart contracts platform"
    - "adding concurrency to smart contracts"
    - "an empirical analysis of smart contracts platforms applications and design patterns"
    - "new kids on the block an analysis of modern blockchains"
    - "optimal selfish mining strategies in bitcoin"
    - "bitcoin transaction graph analysis"

Connected through hyperedge HE-4 (induced by source paper "achieving greater concurrency in execution of smart contracts using object semantics"):
  with members:
    - "hyperledger fabric a distributed operating system for permissioned blockchains"
    - "an efficient framework for optimistic concurrent execution of smart contracts"
    - "a concurrent perspective on smart contracts"
    - "adding concurrency to smart contracts"
    - "an innovative approach to achieve compositionality efficiently using multi version object based transactional systems"
    - "non interference and local correctness in transactional memory"

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.DC(Distributed, Parallel, and Cluster Computing)