Gpu-based Model Of Photoionization And Chemistry In Ionosphere

The numerical model of the ionosphere has the characteristics of complex structure,wide variety of particles,and complicated physical and chemical processes.The calculation of the ionosphere model has the characteristics of large data scale and high time complexity.The theoretical model of the ionosphere is divided into grids according to the Earth's magnetic field coordinate system for calculation.It provides a theoretical basis for the parallel research of the model.The rise of the GPGPU computing field provides a computing platform for the study of the parallel model of the ionosphere.This thesis mainly uses CUDA as the programming platform to study the parallel calculation of photoionization and chemical reaction modes in the ionosphere on the GPU.The thesis mainly focuses on the construction and optimization of the parallel calculation mode of photoionization and chemical reaction as follows:One is the realization and analysis of the serial model of ionosphere photoionization and chemical reaction mode.First,in terms of the model framework,the eccentric tilt dipole coordinate system is selected to simulate the Earth's magnetic field coordinate system,and the geographic coordinate system is converted to the eccentric tilt dipole coordinate system;then the principles and data structure of the daytime mode and night mode of the photoionization mode are analyzed.,The programming logic of photoionization mode is given;finally,the compound process of ion reaction and ion electron is analyzed,and the solution process of chemical reaction mode is given.The second is the construction and optimization of the parallel computing model of the ionosphere photoionization mode.First,analyze the usage of resources such as registers and memory in the photoionization mode,design the data structure of the input and output variables and intermediate variables and the storage location on the GPU;according to the photoionization mode,it has the characteristics of large calculation amount of special functions and many program branches,Split the kernel function to calculate the zenith angle and ionization rate and design the calculation process of the CUDA kernel function;test the zenith angle kernel function and ionization rate kernel function on GPU TITAN Xp respectively Acceleration;finally analyze the data structure of the ionization rate kernel function and the storage structure of the calculation parameters,use Global Memory optimization to reduce the number of accesses to data such as particle density,use Shared Memory to reduce the bandwidth delay of ionization and other parameters,and use Block Size optimization Balanced instruction-level parallelism and thread-level parallelism.Combining the optimized two kernel functions together,the corresponding calculation results are given,and the final acceleration ratio of the photoionization mode is 56.51.The third is the construction and optimization of the chemical reaction model parallel computing model.First of all,according to the execution process of the serial chemical reaction program,the memory usage of a single thread and other resources are analyzed,and the data structure and storage location of related variables in Device and host are given;then the parallel calculation method of chemical reaction is analyzed and given The method of storing chemical reaction equations through two-dimensional arrays and the method of indexing with particle subscripts are used to realize the unification of the models of ion reaction and ion electron composite reaction;the design and implementation of nuclear functions are given according to the execution process of chemical reaction mode;The data scale realizes the test of the chemical reaction parallel computing model,and the average acceleration ratio is 63.8;Finally,the data usage and resource utilization of the parallel kernel function are optimized for Global Memory,Shared Memory,and Block Size,among which Global Memory optimization has been improved The array structure of variables,Shared Memory reduces the storage pressure of registers,and Block Size optimization makes the model balanced at the thread-level parallel and instruction-level parallel.The final acceleration ratio of the experiment is 82.23.Compared with the serial calculation model,the parallel model of photoionization and chemical reaction greatly improves the speed of operation,reduces the calculation resources and equipment costs,and is beneficial to the application of more sophisticated geophysical ionosphere complex models.At the same time,it has certain reference significance for the calculation of related physical models and the calculation of complex chemical reactions.