  Map Space Exploration is the problem of finding optimized mappings of a Deep
Neural Network (DNN) model on an accelerator. It is known to be extremely
computationally expensive, and there has been active research looking at both
heuristics and learning-based methods to make the problem computationally
tractable. However, while there are dozens of mappers out there (all
empirically claiming to find better mappings than others), the research
community lacks systematic insights on how different search techniques navigate
the map-space and how different mapping axes contribute to the accelerator's
performance and efficiency. Such insights are crucial to developing mapping
frameworks for emerging DNNs that are increasingly irregular (due to neural
architecture search) and sparse, making the corresponding map spaces much more
complex. In this work, rather than proposing yet another mapper, we do a
first-of-its-kind apples-to-apples comparison of search techniques leveraged by
different mappers. Next, we extract the learnings from our study and propose
two new techniques that can augment existing mappers -- warm-start and
sparsity-aware -- that demonstrate speedups, scalability, and robustness across
diverse DNN models.
