<div dir="ltr">I have a parallel matrix and I want to extract parts of it locally to create small local matrices. <div><br></div><div>I use PETSC_COMM_SELF for the ISs, but that does not seem to be enough to tell MatCreateSubMatrix that I want a <span style="background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">PETSC_COMM_SELF (sub)matrix.</span></div><div><span style="background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline"><br></span></div><div><span style="background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">How should I do this?</span></div><div><span style="background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline"><br></span></div><div><span style="background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">I am not doing any communication in this process. Could I just wrap the local part of the parallel matrix into a <span style="text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">PETSC_COMM_SELF matrix?</span></span></div><div><span style="background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline"><span style="text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline"><br></span></span></div><div><span style="background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline"><span style="text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">Thanks,</span></span></div><div><span style="background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline"><span style="text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">Mark</span></span></div></div>