Paper:
Achieving faster execution with shorter compilation time can foster further diversity and innovation in neural networks. However, the current paradigm of executing neural networks either relies on hand-optimized libraries, traditional compilation heuristics, or very recently genetic algorithms and other stochastic methods. These methods suffer from frequent costly hardware measurements rendering them not only too time consuming but also suboptimal. As such, we devise a solution that can learn to quickly adapt to a previously unseen design space for code optimization, both accelerating the search and improving the output performance. This solution dubbed CHAMELEON leverages reinforcement learning whose solution takes fewer steps to converge, and develops an adaptive sampling algorithm that not only focuses on the costly samples (real hardware measurements) on representative points but also uses a domain-knowledge inspired logic to improve the samples itself. Experimentation with real hardware shows that CHAMELEON provides 4.45×speed up in optimization time over AutoTVM, while also improving inference time of the modern deep networks by 5.6%.

Review:
This paper proposes an optimizing compiler  for DNN's based on adaptive sampling and reinforcement learning, to drive the search of optimal code in order to reduce compilation time as well as potentially improve the efficiency of the code produced. In particular, the paper proposes to use PPO to optimize a code optimization "search" policy, and then use K-mean clustering over a set of different proposed compilation proposals, from which to perform adaptive sampling to reduce compilation time while still keeping a high diversity of the proposed solution pools during exploration. At the same time the authors claim that using RL will learn a better search strategy compared to random search - such as simulated annealing which is used by competing methods - thus producing faster and better solutions.
The paper show results of up to 4x speedup in compilation time (autotuning time) while obtaining a slightly better or similar efficiency of the generated code (in term of execution time). This is a well written extensive research with good results. The authors mention it is (will be) integrated in the open source code of TVM. However I could find no mention in the paper of whether the code will be released with this publication, and I would like to solicit the authors to clarify their code release strategy and timing.
My other question pertains to whether or not  compilation time is an key metric to target. It is important to some extent, but I would say that aside from exponential / super-polynomial behaviour of auto-tuning algorithms, a multiple hours / days process to create the best optimized code for a certain network / hardware platform might not be such a big hurdle for a community already used to multiple days / weeks / months to train the same models. I believe that focusing on the efficiency of the optimized code produced would probably be a better metric of success.