Re: [petsc-users] [SLEPc] Best method to compute all eigenvalues of a MatShell

2024-05-13 Thread Sreeram R Venkat
I also just ran with cupy.linalg.eigvalsh (which wraps cuSOLVER), and it only took 3.1 seconds. I will probably use this, but it is good to know about the SLEPc cases if I don't need the full spectrum or have sparse matrices, etc. Thanks, Sreeram On Mon, May 13, 2024 at 2:13 PM Sreeram R Venkat

Re: [petsc-users] [SLEPc] Best method to compute all eigenvalues of a MatShell

2024-05-13 Thread Sreeram R Venkat
Apologies, I accidentally hit "reply" instead of "reply-all." Thank you for the reference. Actually, I just tested that N ~ 1e4 case where I had saved the dense matrix to a python-readable format. Using scipy.linalg.eigvalsh, I got the eigenvalues in ~1.5 minutes. They agree with the ones I got fr

Re: [petsc-users] [SLEPc] Best method to compute all eigenvalues of a MatShell

2024-05-13 Thread Jose E. Roman via petsc-users
Please respond to the list. The mpd parameter means "maximum projected dimension". You can think of the projected problem as the "sequential" part of the computation, that is not parallelized ("small" dense eigenproblem). When you run with ZjQcmQRYFpfptBannerStart This

Re: [petsc-users] [SLEPc] Best method to compute all eigenvalues of a MatShell

2024-05-13 Thread Jose E. Roman via petsc-users
Computing the full spectrum is always an unpleasant task. But if you cannot avoid it, I would suggest that you compute the eigenvalues in two runs: n/2 largest real eigenvalues and n/2 smallest real. If your matrix-vector product is cheap, ZjQcmQRYFpfptBannerStart This

Re: [petsc-users] [SLEPc] Best method to compute all eigenvalues of a MatShell

2024-05-13 Thread Matthew Knepley
On Mon, May 13, 2024 at 1:40 PM Sreeram R Venkat wrote: > I have a MatShell object that computes matrix-vector products of a dense > symmetric matrix of size NxN. The MatShell does not actually form the dense > matrix, so it is never in memory/storage. For my application, N ranges from > 1e4 to 1

[petsc-users] [SLEPc] Best method to compute all eigenvalues of a MatShell

2024-05-13 Thread Sreeram R Venkat
I have a MatShell object that computes matrix-vector products of a dense symmetric matrix of size NxN. The MatShell does not actually form the dense matrix, so it is never in memory/storage. For my application, N ranges from 1e4 to 1e5. I want to compute the full spectrum of this matrix. For an ex