1. Norwegian Research Center NORCE, Nygårdsgaten 112, 5008 Bergen, Norway.
2. Department of Mathematics, University of Oslo, 0316 Oslo, Norway.
3. Corresponding author. Henan Academy of Big Data, Zhengzhou University, Zhengzhou 450052, People’s Republic of China, and School of Mathematics and Statistics, Zhengzhou University, Zhengzhou 450001, People’s Republic of China.
4. LSEC, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China, and School of Mathematical Science, University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China.