On 27 Aug 2013, at 16:25, Jose E. Roman <[email protected]> wrote: > > El 27/08/2013, a las 16:18, Jed Brown escribió: > >> John Travers <[email protected]> writes: >> >>> Hi all, >>> >>> I'm trying to use shift and invert to find interior eigenvalues using slepc. >>> I am using example 4 in slepc 3.41 which reads the matrix from a binary >>> file ('A' saved from Matlab). >>> >>> If I run just: >>> ./ex4 -file A -eps_nev 1 >>> the program runs fine, and correctly finds the largest eigenvalue (although >>> much slower than Matlab's eigs). >> >> You can't compare performance when running in debug mode. If the >> algorithm converges slower, we can figure out why. >> >>> However, if I run: >>> ./ex4 -file A -eps_nev 1 -st_type sinvert -st_shift 0.0,0.5 >>> to try and find an eigenvalue near 0.0+0.5i, it outputs the error message >>> below. >> >> Please just insert a value 0.0 along the diagonal of your matrix. >> MatShift would be more expensive and could hide memory performance bugs >> if it silently reallocated to add diagonal entries. > > Note that you should use -eps_target 0.0,0.5 instead of -st_shift.
OK, thanks for the heads up.
