#include "slepcst.h" PetscErrorCode STSetMatMode(ST st,STMatMode mode)Logically Collective on ST
st | - the spectral transformation context | |
mode | - the mode flag, one of ST_MATMODE_COPY, ST_MATMODE_INPLACE or ST_MATMODE_SHELL |
With ST_MATMODE_INPLACE, the original matrix A is shifted at STSetUp() and unshifted at the end of the computations. With respect to the previous one, this mode avoids a copy of matrix A. However, a backdraw is that the recovered matrix might be slightly different from the original one (due to roundoff).
With ST_MATMODE_SHELL, the solver works with an implicit shell matrix that represents the shifted matrix. This mode is the most efficient in creating the shifted matrix but it places serious limitations to the linear solves performed in each iteration of the eigensolver (typically, only interative solvers with Jacobi preconditioning can be used).
In the case of generalized problems, in the two first modes the matrix A - s B has to be computed explicitly. The efficiency of this computation can be controlled with STSetMatStructure().
Location: src/st/interface/stset.c
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