  The rising usage of AI and ML-based processing across application domains has
exacerbated the need for low-cost ML implementation, specifically for
resource-constrained embedded systems. To this end, approximate computing, an
approach that explores the power, performance, area (PPA), and behavioral
accuracy (BEHAV) trade-offs, has emerged as a possible solution for
implementing embedded machine learning. Due to the predominance of MAC
operations in ML, designing platform-specific approximate arithmetic operators
forms one of the major research problems in approximate computing. Recently
there has been a rising usage of AI/ML-based design space exploration
techniques for implementing approximate operators. However, most of these
approaches are limited to using ML-based surrogate functions for predicting the
PPA and BEHAV impact of a set of related design decisions. While this approach
leverages the regression capabilities of ML methods, it does not exploit the
more advanced approaches in ML. To this end, we propose AxOCS, a methodology
for designing approximate arithmetic operators through ML-based supersampling.
Specifically, we present a method to leverage the correlation of PPA and BEHAV
metrics across operators of varying bit-widths for generating larger bit-width
operators. The proposed approach involves traversing the relatively smaller
design space of smaller bit-width operators and employing its associated
Design-PPA-BEHAV relationship to generate initial solutions for
metaheuristics-based optimization for larger operators. The experimental
evaluation of AxOCS for FPGA-optimized approximate operators shows that the
proposed approach significantly improves the quality-resulting hypervolume for
multi-objective optimization-of 8x8 signed approximate multipliers.
