Thank you very much, moving around the endpoints of the interval did indeed solve my problem.
Best regards, --- Desforges Perceval Le 2018-09-17 17:51, Jose E. Roman a écrit : > This can happen sometimes when the chosen interval for spectrum slicing is to > large or the endpoints of the interval are too far away from the eigenvalues. > Try moving the endpoints of the interval closer to the eigenvalues. > > Jose > >> El 17 sept 2018, a las 17:24, Desforges Perceval >> <[email protected]> escribió: >> >> Hello PETSc developpers, >> >> I have been using SLEPc and PETSc for solving my sparse systems for a small >> time now, and have been very satisfied with everything. >> >> However, I have been running into an error lately, and I have been unable to >> find any online resource that talks about this specific error. >> >> I use SLEPc to find all the eigenvalues of certain tridiagonal and symmetric >> matrices. I set the solver to find all the eigenvalues in a large interval >> ([0;10] for example) using the spectrum splicing technique. I use MUMPS >> because I would like to perform this calculation in parallel later on, but >> for now I am doing it sequentially. >> >> While the solver works very well for small enough matrices (n=2000), when I >> increase the matrix size to around 10000, I get this error that I do not >> really understand: >> >> [0]PETSC ERROR: First shift renders no information >> >> Could someone please enlighten me as to what this error means? I don't know >> if it's relevant but I am using older version of PETSc (3.8.4) and SLEPc >> (3.8.2). >> >> I apologize in advance if this question has been answered somewhere already. >> >> Thank you very much, >> >> Sincerely, >> >> Desforges Perceval
