区块链智能合约交易并行执行模型综述

以太坊等区块链采用串行方式执行区块中的智能合约交易，虽能严格保障执行后节点间区块链状态的一致性，但这已成为目前制约区块链吞吐率的一个重要瓶颈.因此，采用并行方法优化智能合约交易的执行逐渐成为工业界和学术界关注的重点.总结了区块链智能合约并行执行方法的研究进展，提出了一个研究框架，该框架以智能合约并行执行的阶段为视角，凝练出4种智能合约并行执行模型，即基于静态分析的并行执行模型、基于动态分析的并行执行模型、节点间并行执行模型和分治并行执行模型，然后描述了每种模型下典型的并行执行方法.最后，对交易依赖图和并发控制策略等影响并行执行的因素进行了讨论，并提出了未来可研究的方向.

Overview on Parallel Execution Models of Smart Contract Transactions in Blockchains

Blockchains such as Ethereum serially execute smart contract transactions in a block, which can strictly guarantee the consistency of the blockchain state between nodes after execution, but it has become a serious bottleneck restricting the throughput of these blockchains. Therefore, the use of parallel methods to optimize the execution of smart contract transactions has gradually become the focus of industry and academia. This study summarizes the research progresses of the parallel execution methods of smart contracts in blockchains, and proposes a research framework. From the perspective of the phases of parallel execution of smart contracts, the framework condenses four parallel execution models of smart contracts, namely the parallel execution model based on static analysis, the parallel execution model based on dynamic analysis, the parallel execution model between nodes and the divide-and-conquer parallel execution model, and describes the typical parallel execution methods under each model. Finally, this study discusses the factors affecting parallel execution such as the transaction dependency graph and concurrency control strategies, and proposes future research directions.