COMSOL Multiphysics™

femsolver
ADVANCED SOLVER PARAMETERS
The section “Advanced Solver Parameters” on page 435 in the COMSOL
Multiphysics User’s Guide describes the features corresponding to the properties
Blocksize, Complexfun, Conjugate, Keep, Method, Nullfun, Rowscale,
Solfile, and Uscale.
The property Assemtol affects the assembled matrices, see assemble for details.
By default, COMSOL Multiphysics gives an error message if the solver encounters
an undefined mathematical operation when solving the model, for instance 0/0 or
log(0). If you instead want the solver to proceed, put the property Matherr=off.
Then 0/0=NaN (not a number) and log(0)=-Inf.
The Symmetric and Conjugate properties correspond to the Solver Parameters
dialog box settings Matrix symmetry and Use Hermitian transpose in constraint matrix
and in symmetry detection according to the following table:
Matrix
symmetry
Use Hermitian
transpose...
Automatic Automatic Nonsymmetric Nonsymmetric Symmetric Hermitian
cleared selected cleared selected n.a. n.a.
Symmetric auto auto off off on on
Conjugate off on off on off on
The property Keep corresponds to the manual control of reassembly feature. Its
value can be a string containing the letters D, E, K, L, M, N or the string auto. These
letters have the following meaning: E=constant mass, D=constant damping,
K=constant Jacobian, L=constant load, M=constant constraint, N=constant constraint
Jacobian (see “Manual Control of Reassembly” on page 439 in the COMSOL
Multiphysics User’s Guide).
For the Nullfun property, flnullorth is the orthonormal null-space function, and
flspnull is the sparse null-space function.
If Solfile=on, the solution is stored on a temporary file. The Solfilename
property can be used to give the full path name of the file. A part of the solution is
stored in memory in a few blocks (usually 1-5 blocks reside in memory). The
maximum block size (in megabytes) can be controlled with the property
Solfileblock.
The property Uscale determines a scaling of the degrees of freedom that is applied
in order to get a more well-conditioned system; see “Scaling of Variables and
152 | CHAPTER 1: COMMAND REFERENCE