A Linear Frequency Principle Model to Understand the Absence of Overfitting in Neural NetworksSupported by the National Key R&D Program of China (Grant No. 2019YFA0709503), the Shanghai Sailing Program, the Natural Science Foundation of Shanghai (Grant No. 20ZR1429000), the National Natural Science Foundation of China (Grant No. 62002221), Shanghai Municipal of Science and Technology Project (Grant No. 20JC1419500), and the HPC of School of Mathematical Sciences at Shanghai Jiao Tong University. (March 2021)