FPGA-Based Accelerator Architectures for Large-Scale Quantum Annealing with Fully-Connected Ising Models

Hasitha Muthumala Waidyasooriya, Masanori Hariyama, Masamichi J. Miyama +1 more

Hasitha Muthumala Waidyasooriya, Yuta Ohma, Masanori Hariyama

Quantum annealing (QA) is a probabilistic approx-imation method to find the global optimum of a combinatorial optimization problem. QA is done on quantum annealers such as D-wave using quantum properties. Since the number of qubits in quantum annealers is limited, it is difficult to use those to solve large-scale real-world problems. Therefore, quantum annealing simulation on digital computers is necessary. In this paper, we discuss an FPGA based quantum annealing simulator for sparse Ising model. Unlike a fully-connected Ising model, the number of connections among spins in sparse model is limited. Highly sparse Ising models require significantly low amount of computations while allowing more parallel operations. One the other hand, sparsity and the connections among spins are not the same for different Ising models, and it is difficult to propose one specific accelerator architecture for all. We propose a method to automatically generate an application specific accelerator archi-tecture for a given sparse Ising model. The proposed accelerator fully exploits the parallelism to increase the processing speed. We design an FPGA prototype of the proposed accelerator and confirmed the correct behavior. In future, we expect to extend the proposed method to execute large quantum annealing simulations using multiple FPGAs.

Evelina Forno

Mark W. Johnson

Dong Jiang, Xiangrui Wang, Zhanhong Huang +3 more

The Ising annealing processor has emerged as a promising approach to accelerate the discovery of the optimal solutions for a wide range of combinatorial optimization problems (COPs), by mapping various COPs into a unified Ising model. However, fixed computational strategies and inflexible architectures make previous designs suffer from a low hardware resource utilization rate when the numbers of the total required and real-time flipped spins vary across different COPs and iteration steps. In this paper, a novel spin scale-aware self-adaptive Ising annealing processing architecture (AIAPA) is proposed to address this problem, with an adaptive computational strategy, a custom instruction set, multi-traffic mode routers, and a fully-pipelined computing array. It can dynamically adapt to the varying scenarios during the Ising annealing process to maximize the performance of limited hardware resources. Its prototype, supporting 65k fully-connected spins, is implemented on an FPGA platform, operates at a clock frequency of 188 MHz. The AIAPA achieves up to a 24.22 times faster annealing speed compared to the state-of-the-art FPGA design on the max-cut optimization problem while maintaining a high convergence accuracy.

Chia-Yin Liu, Hasitha Muthumala Waidyasooriya, Masanori Hariyama

Quantum Annealing (QA) is a classical probabilistic algorithm that provides a heuristic to find the globally optimal solution for a combinatorial optimization problem by using quantum tunneling processes. Quantum annealing simulation can be implemented on Field Programmable Gate Arrays (FPGAs) using Quantum Monte Carlo (QMC) simulation in the transverse Ising model. Since input data of the QMC simulation increases exponentially with the problem size, we have to use the DRAM of an FPGA board to store these data. However, storing data in DRAM causes two problems. One is the limited data access bandwidth, and the other is the limitation of DRAM capacity. We propose a data-transfer-bottleneck-less FPGA-based accelerator for quantum annealing simulation and apply it to implement number partitioning problem, which is one of the combinatorial optimization problems. The critical idea of our architecture is not storing but computing the large data in FPGA kernels and eliminating the burden on data transfer. We implement the proposed architecture on Stratix 10 FPGA and achieve up to 39.6 times speed-up compared to CPU-based quantum annealing simulation. We also achieve up to 2.8 times speed-up and implement 262,144 spins, which is 64 times increase compared to the most recent FPGA implementation.