Advanced

Handle advanced general solver properties.

model.sol(sname).feature(solv).create(fname,"Advanced")

model.sol(sname).feature(solv).feature(fname).set(pname,value)

Feature for a number of advanced solver settings and assembly settings.

Table 6-25: Valid General Property/value Pairs for Advanced
Property	Values	Default	Description
assemtol	0 or a positive double	1e-12	Drop tolerance for
autorescale	on \| off	on	Automatic rescaling of linear equations (for the Stationary solver).
blocksize	positive integer \| auto	auto	Assembly block size.
cachepattern	true \| false	false	Reuse sparsity pattern during assembly.
checkmatherr	on \| off	off	Check for undefined numerical values after each operation.
complexfun	on \| off	off	Use complex-valued functions with real input.
convinfo	on \| detailed \| off	on	Print info to log.
D, E, K, L, M, N	on \| off		Manual control of reassembly.
keep	on \| off		Manual control of reassembly.
logsampling	double, zero or positive	0.005	Minimum time (in seconds) for log sampling of time-dependent solvers.
matherr	on \| off	on	Error for undefined operations.
matrixformat	auto \| sparse \| filled \| matrixfree	auto	Matrix format.
orthonormallimit	double	1e7	Limit, as an estimate of the complexity (number of operations), for using the orthonormal method in the automatic null-space function.
nullfun	flnullorth \| flspnull \| auto\|explicitorth\| explicitsp	auto	Null-space function.
rowscale	on \| off	on	Equilibrate rows.
storeresidual	off \| solving \| solvingandoutput	off	Store the latest residual while solving or while solving and in the output.
symmetric	auto \| on \| off \| hermitian	auto	Symmetric matrices.

The Advanced section in the COMSOL Multiphysics Reference Manual, describes the functionality corresponding to the properties blocksize, complexfun, nullfun, and rowscale.

You can use the property symmetric to tell the solver that the model is symmetric or Hermitian, or you can use the automatic feature to find out (see Advanced in the COMSOL Multiphysics Reference Manual).

You can set convinfo=detailed to print more detailed information about the solver process in the log window. For example information about individual linear iterations or the scales per field computed by the automatic scaling algorithm. When convinfo=off, only minimal information about the solution process is printed.

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 properties keep and D, E, K, L, M, and N allow manual control of reassembly. If keep=on, each of the other properties controls reassembly of a specific matrix or vector. Setting the property value to on, means that the quantity is constant, and therefore can be assembled once and then kept. The letters have the following meaning: E=constant mass, D=constant damping, K=constant Jacobian, L=constant load, M=constant constraint, N=constant constraint Jacobian.

The autorescale property control if the automatically computed scales should be recomputed. This property only affects stationary nonlinear problems and fields that are using the automatic scaling method and for the constant damping technique. The initially computed scales are based on the initial assembled matrix. When autorescale=on the scales are recomputed in each nonlinear iteration based on the current solution.

You can use the property matrixformat to tell the solver which matrix format to store the system matrices in:

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sparse stores the matrix in a sparsely populated matrix format.

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filled stores the matrix in a densely populated format.

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matrixfree does not store matrices. The effects of matrix operations are assembled when needed.

When you specify auto (the default), the format is automatically determined based on the solver used.

By default, COMSOL does not check for undefined numerical values (for example, from numerical overflow) after each numerical operation. Set the property checkmatherr to on to make COMSOL check for such undefined numerical values, which will give more accurate error messages if such undefined numerical values occur.