FlexScore: Quantifying Flexibility

Domain-specific accelerators achieve high performance and efficiency at the cost of reduced adaptivity to functionality changes, i.e., flexibility. Balancing efficiency and flexibility is important for accelerator designing. There is not, however, a commonly accepted metric for flexibility. We propose FlexScore as a flexibility metric based on the relationship between flexibility and goodness metrics, such as performance. FlexScore does not incorporate domain-specific or hardware-specific knowledge and, thus, is applicable to general accelerator design. We present FlexScores of three well-known DNN accelerators and observe that there is 45 percent FlexScore difference among them and show how architectural changes could improve FlexScore by up to 21 percent, demonstrating the usefulness of FlexScore in evaluating, comparing, and trading-off different architectures.