<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="">Hi, </div><div class=""><br class=""></div><div class=""> I am currently accessing PETSc through libMesh where the matrices of type MPIAIJ are being initialized using the MatSetSizes, MatSetFromOptions, and MatMPIAISetPreallocation calls. </div><div class=""><br class=""></div><div class=""> I am interested in accessing the BDDC solver and have looked through the PDF manual that talks about BDDC setup through MATIS. However, it is not clear what would be the most efficient route to accessing BDDC for my unstructured FE code. </div><div class=""><br class=""></div><div class=""> Example 72 (<a href="https://www.mcs.anl.gov/petsc/petsc-3.10/src/ksp/ksp/examples/tutorials/ex72.c.html" class="">https://www.mcs.anl.gov/petsc/petsc-3.10/src/ksp/ksp/examples/tutorials/ex72.c.html</a>) seems to be calling MatConvert to make the conversion to MATIS. However, the documentation of MATIS says that <a href="https://www.mcs.anl.gov/petsc/petsc-3.10/docs/manualpages/Mat/MatSetLocalToGlobalMapping.html#MatSetLocalToGlobalMapping" style="font-family: -webkit-standard;" class="">MatSetLocalToGlobalMapping</a> should be called before initializing MATIS, which is not done in Example 72. I am also not sure if I need to setup any DM/DA constructs to aid in this process. </div><div class=""><br class=""></div><div class=""> I would appreciate if someone could provide an outline of steps required to make the conversion of MatMPIAIJ in order to use BDDC/FETI preconditioners. </div><div class=""><br class=""></div><div class="">Thanks,</div><div class="">Manav</div><div class=""><br class=""></div></body></html>