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. Precise and rapid air quality simulations and forecasting arelimited by the computational performance of the air quality model used, andthe gas-phase chemistry module is the most time-consuming function in the airquality model. In this study, we designed a new framework for the widely usedthe Carbon Bond Mechanism Z (CBM-Z) gas-phase chemical kinetics kernel toadapt the single-instruction, multiple-data (SIMD) technology in next-generationprocessors to improve its calculation performance. Theoptimization implements the fine-grain level parallelization of CBM-Z byimproving its vectorization ability. Through constructing loops andintegrating the main branches, e.g., diverse chemistry sub-schemes, multiplespatial points in the model can be operated simultaneously on vectorprocessing units (VPUs). Two generation CPUs – Intel Xeon E5-2680 V4 CPU andIntel Xeon Gold 6132 – and Intel Xeon Phi 7250 Knights Landing (KNL) areused as the benchmark processors. The validation of the CBM-Z module outputsindicates that the relative bias reaches a maximum of 0.025 % after 10 hintegration with -fp-model fast  =1 compile flag. The results ofthe module test show that the Multiple-Points CBM-Z (MP CBM-Z) resulted in5.16 × and 8.97 × speedup on a single core of Intel Xeon E5-2680V4 and Intel Xeon Gold 6132 CPUs, respectively, and KNL had a speedup of3.69 × compared with the performance of CBM-Z on the Intel Xeon E5-2680V4 platform. For the single-node tests, the speedup on the two generationCPUs can reach 104.63 × and 198.50 × using message passinginterface (MPI) and 101.02 × and 194.60 × using OpenMP, and thespeedup on the KNL node can reach 175.23 × using MPI and 167.45 × using OpenMP. The speedup ofthe optimized CBM-Z is approximately 40 % higher on a one-socket KNLplatform than on a two-socket Broadwell platform and about 13 %–16 %lower than on a two-socket Skylake platform. We also tested athree-dimensional chemistry transport model (CTM) named Nested Air QualityPrediction Model System (NAQPMS) equipped with the MP CBM-Z. The testsillustrate an obvious improvement on the performance for the CTM afteradopting the MP CBM-Z. The results show that the MP CBM-Z leads to a speedupof 3.32 and 1.96 for the gas-phase chemistry module and the CTM on the IntelXeon E5-2680 platform. Moreover, on the new Intel Xeon Gold 6132 platform,the MP CBM-Z gains 4.90 × and 2.22 × speedups for the gas-phasechemistry module and the whole CTM. For the KNL, the MP CBM-Z enables a3.52 × speedup for the gas-phase chemistry module, but the whole modellost 24.10 % performance compared to the CPU platform due to the poorperformance of other modules. In addition, since this optimization seeks toimprove the utilization of the VPU, the model is more suitable for the newgeneration processors adopting the more advanced SIMD technology. The resultsof our tests already show that the benefit of updating CPU improved by about47 % by using the MP CBM-Z since the optimized code has betteradaptability for the new hardware. This work improves the performance of theCBM-Z chemical kinetics kernel as well as the calculation efficiency of theair quality model, which can directly improve the practical value of the airquality model in scientific simulations and routine forecasting.

MP CBM-Z V1.0: design for a new Carbon Bond Mechanism Z (CBM-Z) gas-phase chemical mechanism architecture for next-generation processors