Spin-Hall-Effect-Based Stochastic Number Generator for Parallel Stochastic Computing

Stochastic computing (SC) is a promising technology that can be used for low-cost hardware designs. However, SC suffers from its long latency. Although parallel processing can efficiently shorten the latency, duplicated stochastic number generators (SNGs) are necessary, which cause substantial hardware overhead. This paper proposes a scalable SNG based on the spin-Hall-effect (SHE), which is capable of generating multiple independent stochastic streams simultaneously. The design takes advantages of the efficient charge-to-spin conversion from the Spin-Hall material and the intrinsic stochasticity of nanomagnets. Compared to previous spintronic SNGs, the SHE-SNG can reduce the area by <inline-formula> <tex-math notation="LaTeX">$1.6\times -7.8\times $ </tex-math></inline-formula> and the power by <inline-formula> <tex-math notation="LaTeX">$4.9\times -13\times $ </tex-math></inline-formula> while increasing the degree of parallelism from 1 to 16. Compared to CMOS-based SNGs, the proposed SNG obtained <inline-formula> <tex-math notation="LaTeX">$24\times -120\times $ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$53\times $ </tex-math></inline-formula> reduction in terms of area and power, respectively. Finally, three benchmarks were implemented, and the results indicate that SC implementations with the proposed SHE-SNG can achieve <inline-formula> <tex-math notation="LaTeX">$1.2\times -29\times $ </tex-math></inline-formula> reduction of hardware resources compared to implementations with previous CMOS- and spintronic-based designs while scaling the degree of parallelism from 1 to 64.