Discovering the In-Memory Kernels of 3D Dot-Product Engines

The capability of resistive random access memory (ReRAM) to implement multiply-and-accumulate operations promises unprecedented efficiency in the design of scientific computing applications. While the use of two-dimensional (2D) ReRAM crossbar has been well investigated in the last few years, the design of in-memory dotproduct engines using three-dimensional (3D) ReRAM crossbars remains a topic of active investigations. In this paper, we holistically explore how to leverage 3D ReRAM crossbars with several (2 to 7) stacked crossbar layers. In contrast, previous studies have focused on 3D ReRAM with at most 2 stacked crossbar layers. We first discover the in-memory compute kernels that can be realized using 3D ReRAM with multiple stacked crossbar layers. We discover that matrices with different sparsity patterns can be realized by appropriately assigning the inputs and outputs to the perpendicular metal wires within the 3D stack. We present a design automation tool to map sparse matrices within scientific computing applications to the discovered 3D kernels. The proposed framework is evaluated using 20 applications from the SuitSparse Matrix Collection. Compared with 2D crossbars, the proposed approach using 3D crossbars improves area, energy, and latency with 2.02X, 2.37X, 2.45X, respectively.