Hi, Ithink that the topic is more suited for PETSc-developers than its users; therefore, I move it to the dev list. Continuing the discussion on implementing a variable-block size BILU preconditioner, would it be possible to change the block size parameter (bs) on BAIJ format such that it can handle variable block sizes? (i.e., instead of it being a scalar, it can be an array). Although BILU does not necessarily require rectangular blocks, I think, it leads to less messy code. Also, being a newbie on PETSc code, I do not understand some parts of the code, especially distributed matrix storage and some of the implemented numerical algorithms. Is there any reference that I can use for this? -- Ali Reza Khaz’ali Assistant Professor of Petroleum Engineering, Department of Chemical Engineering Isfahan University of Technology Isfahan, Iran