The two-volume set LNCS 11973 and 11974 constitute revised selected papers from the Third International Conference on Numerical Computations, NUMTA 2019, held in Crotone, Italy, in June 2019. The total of 53 full and 50 short papers presented in the proceedings was carefully reviewed and selected from 223 submissions. The papers of part I have been preselected by PC Members and organizers of special session before submission and revieweing to ensure high research standards of submissions for this volume. They were organized in the following topical sections: approximation: methods, algorithms, and applications; computational methods for data analysis; first order methods in optimization: theory and applications; high performance computing in modelling and simulation; numbers, algorithms, and applications.weiterlesen