Dear PETSc developers: Hi, During the process of testing the program, I found some questions about SNES. These are some basic questions that I have overlooked. Please help me to answer them. 1. Because my program uses - snes_mf_operator, there is no Jacobian matrix. Linear and non-linear step residuals are different in petsc. The linear step residuals are r_linear = J*δx-f(x). Since I don't have a Jacobian matrix, I don't know how to calculate the relative residuals of linear steps provided in petsc. Do we use the finite difference approximation matrix vector product when calculating the residuals? 2. Read the user's manual for a brief introduction to the inexact Newton method, but I am very interested in the use of this method. I want to know how to use this method in petsc. 3. The default line search used by SNES in PETSc is bt, which often fails in program debugging. I don't know much about linesearch, and I'm curious to know why it failed. How can I supplement this knowledge?
Thanks, Yingjie
