Recently, there has been a growing demand for the deployment of Explainable
Artificial Intelligence (XAI) algorithms in real-world applications. However,
traditional XAI methods typically suffer from a high computational complexity
problem, which discourages the deployment of real-time systems to meet the
time-demanding requirements of real-world scenarios. Although many approaches
have been proposed to improve the efficiency of XAI methods, a comprehensive
understanding of the achievements and challenges is still needed. To this end,
in this paper we provide a review of efficient XAI. Specifically, we categorize
existing techniques of XAI acceleration into efficient non-amortized and
efficient amortized methods. The efficient non-amortized methods focus on
data-centric or model-centric acceleration upon each individual instance. In
contrast, amortized methods focus on learning a unified distribution of model
explanations, following the predictive, generative, or reinforcement
frameworks, to rapidly derive multiple model explanations. We also analyze the
limitations of an efficient XAI pipeline from the perspectives of the training
phase, the deployment phase, and the use scenarios. Finally, we summarize the
challenges of deploying XAI acceleration methods to real-world scenarios,
overcoming the trade-off between faithfulness and efficiency, and the selection
of different acceleration methods.Comment: 15 pages, 3 figure