Architectural Design Space Exploration (DSE) is a notoriously difficult problem due to the exponentially large size of the design space and long simulation times. Previously, many studies proposed to formulate DSE as a regression problem which predicts architecture responses (e.g., time, power) of a given architectural configuration. Several of these techniques achieve high accuracy, though often at the cost of significant simulation time for training the regression models. We argue that the information the architect mostly needs during the DSE process is whether a given configuration will perform better than another one in the presences of design constraints, or better than any other one seen so far, rather than precisely estimating the performance of that configuration. Based on this observation, we propose a novel ranking-based approach to DSE where we train a model to predict which of two architecture configurations will perform best. We show that, not only this ranking model more accurately predicts the relative merit of two architecture configurations than an ANN-based state-of-the-art regression model, but also that it requires much fewer training simulations to achieve the same accuracy, or that it can be used for and is even better at quantifying the performance gap between two configurations. We implement the framework for training and using this model, called ArchRanker, and we evaluate it on several DSE scenarios (unicore/multicore design spaces, and both time and power performance metrics). We try to emulate as closely as possible the DSE process by creating constraint-based scenarios, or an iterative DSE process. We find that ArchRanker makes 29.68% to 54.43 % fewer incorrect predictions on pair-wise relative merit of configurations (tested with 79,800 configuration pairs) than an ANN-based regression model across all DSE scenarios considered (values averaged over all benchmarks for each scenario). We also find that, to achieve the same accuracy as ArchRanker, the ANN often requires three times more training simulations.
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