<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 have an application that uses the KSP solver and I am looking at the performance with increasing system size. I am currently running on MacBook Pro with 32 GB memory and Petsc obtained from GitHub (commit <span style="color: rgb(159, 160, 28); font-family: Monaco; font-size: 10px; background-color: rgba(0, 0, 0, 0.85);" class="">df0e43005dbe6ff47eff22a32b336a6c37d02c3a</span>). </div><div class=""><br class=""></div><div class=""> The application runs fine till about 2e6 DoFs using gamg without any problems. </div><div class=""><br class=""></div><div class=""> However, when I try a larger system size, in this case with 5.4e6 DoFs, the application hangs for an hour and I have to kill the MPI processes. </div><div class=""><br class=""></div><div class=""> I tried to use Xcode Instruments to profile the 8 MPI processes and I have attached a screenshot of the recorded results from each process. All processes are stuck inside MatAssemblyEnd, but at different function calls. </div><div class=""><br class=""></div><div class=""> I am not sure how to debug this issue, and would greatly appreciate any guidance. </div><div class=""><br class=""></div><div class=""> For reference, I am calling PETSc with the following options:</div><div class=""> <span style="color: rgb(16, 16, 16); font-family: Monaco; font-size: 10px; background-color: rgba(255, 255, 255, 0.85);" class="">-ksp_type gmres -pc_type gamg -mat_block_size 3 -mg_levels_ksp_max_it 4 -ksp_monitor -ksp_converged_reason</span></div><div class=""><br class=""></div><div class="">Regards,</div><div class="">Manav</div><div class=""><br class=""></div><img apple-inline="yes" id="7D54CA5B-4CB4-4D05-83ED-28DCCFC6F21A" src="cid:82916A27-7372-4663-A57E-3BE39C85527C" class=""><img apple-inline="yes" id="B1B6D50E-68C6-4474-98F1-77220A5A36D6" src="cid:AA5E7E79-A39C-45B3-9CF4-E22CA4A51F71" class=""><img apple-inline="yes" id="89AAD486-E7A0-4483-984A-EF3DDDC2DF7C" src="cid:80113EBA-8541-4B2D-B614-CA3816E47ABC" class=""><img apple-inline="yes" id="F7DCDCCF-D4A5-494B-A432-F85125EEB597" src="cid:9C2AC63A-7866-49A0-90EB-C8FCB52BE1FF" class=""><img apple-inline="yes" id="15A00772-D8C9-4B45-83FB-7F3C0E78624D" width="968" height="673" src="cid:075284F6-52F1-44AA-9E5D-44F078992AA5" class=""><img apple-inline="yes" id="0F434653-9CDC-4FE7-911B-1B0F551D4CF4" width="968" height="673" src="cid:CF513C2B-C410-4F77-AF13-C98A10D6F622" class=""><img apple-inline="yes" id="A9C63439-3A1B-45BD-B689-9247997E2AD5" width="968" height="673" src="cid:CF43FC07-669D-4721-BCF7-84C5800FEC60" class=""><img apple-inline="yes" id="4365EE4C-817A-46ED-ACE8-9FE87949A98C" width="1012" height="748" src="cid:94394194-204D-47E3-8865-EFBE71BDFA64" class=""></body></html>