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arXiv 2202.01869cs.LGstat.ME
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Hawkes过程建模的柔性触发核

Flexible Triggering Kernels for Hawkes Process Modeling

Duke University(杜克大学);Stanford University(斯坦福大学)

Yamac Alican Isik, Connor Davis, Paidamoyo Chapfuwa, Ricardo Henao

摘要:

最近提出的用于Hawkes过程建模的编码器-解码器结构使用transformer启发的架构,其通过嵌入和自注意机制对事件的历史进行编码。这些模型比基于RNN的模型提供更好的预测和拟合优度。然而,它们通常需要高计算和存储器复杂性要求,并且有时无法充分捕获底层过程的触发功能。因此,出于动机,我们引入了一个有效的和一般的编码的历史事件序列,通过替换复杂的(多层)注意结构与观察到的数据的触发内核。注意到点过程的触发内核和注意力分数之间的相似性,我们使用触发内核来取代用于构建历史表示的权重。我们对触发函数的估计配备了S形门控机制,该机制捕获了标准随时间衰减内核具有挑战性的本地触发效应。此外,将事件类型表示和时间嵌入作为输入,模型在给定事件类型对的情况下学习底层触发类型-时间内核参数。我们对竞争模型广泛使用的合成和真实数据集进行了实验,同时进一步包括COVID-19数据集,以说明纵向协变量可用的情况。结果表明,该模型优于现有的方法,同时更有效的计算复杂性,并通过直接应用新引入的内核产生可解释的结果。

英文摘要:

Recently proposed encoder-decoder structures for modeling Hawkes processes use transformer-inspired architectures, which encode the history of events via embeddings and self-attention mechanisms. These models deliver better prediction and goodness-of-fit than their RNN-based counterparts. However, they often require high computational and memory complexity requirements and sometimes fail to adequately capture the triggering function of the underlying process. So motivated, we introduce an efficient and general encoding of the historical event sequence by replacing the complex (multilayered) attention structures with triggering kernels of the observed data. Noting the similarity between the triggering kernels of a point process and the attention scores, we use a triggering kernel to replace the weights used to build history representations. Our estimate for the triggering function is equipped with a sigmoid gating mechanism that captures local-in-time triggering effects that are otherwise challenging with standard decaying-over-time kernels. Further, taking both event type representations and temporal embeddings as inputs, the model learns the underlying triggering type-time kernel parameters given pairs of event types. We present experiments on synthetic and real data sets widely used by competing models, while further including a COVID-19 dataset to illustrate a scenario where longitudinal covariates are available. Results show the proposed model outperforms existing approaches while being more efficient in terms of computational complexity and yielding interpretable results via direct application of the newly introduced kernel.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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