COMSOL Multiphysics™

flnull
Purpose
flnull
Compute null space of a matrix, its complement, and the range of the matrix.
Syntax
Range = flnull(N,...)
[Null,Compl] = flnull(N,...)
[Null,Compl,Range] = flnull(N,...)
[...] = flnull('in',{...},'out',{...},...)
Description Range = flnull(N,...) computes the range of N.
[Null,Compl] = flnull(N,...) computes the null space of N and its
complement.
[Null,Compl,Range] = flnull(N,...) computes null space, its complement,
and the range of N.
[...] = flnull('in',{...},'out',{...},...) compute null space, its
complement, and the range of N.
The function flnull accepts the following property/value pairs:
TABLE 1-47: VALID PROPERTY/VALUE PAIRS
PROPERTY
NAME
PROPERTY VALUE DEFAULT DESCRIPTION
In N | NT N Input matrices
Nullfun flnullorth | auto
Null-space function
flspnull | auto
Out Null | Range |
Compl
Output variables
The property Nullfun selects the null-space algorithm. The algorithm flnullorth
computes a orthonormal basis for the null space by using singular value
decomposition in a block-wise pattern. The method flspnull handles constraint
matrices with non-local couplings by employing a sparse algorithm. The auto
method automatically selects the most appropriate of flnullorth and flspnull.
See the sections “Advanced Solver Parameters” on page 435 and “Constraint
Handling” on page 441 in the COMSOL Multiphysics User’s Guide for further
information on the use of these matrices.
Example
The Poisson Equation on the Unit Disk
Solve this problem by elimination. The example illustrates the way femstatic
handles the constraints internally by the default constraint handling method:
eliminate.
clear fem
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