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How to calculate/export left eigenvectors within the eigenvalue solver?
Posted Apr 23, 2020, 4:49 p.m. EDT Acoustics & Vibrations, LiveLink for MATLAB, Studies & Solvers Version 4.4 0 Replies
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Dear COMSOL users/employees,
after quite some research, I still haven't found a way to calculate and export the left eigenvector to Matlab when performing an eigenvalue study in COMSOL.
Some background on the issue: Currently I am trying to perform reduced order model simulations in time domain for acoustic wave propagation. The governing equations are implemented using the Weak Form PDE Physics in COMSOL 4.4 (newer releases are available but rarely used). Therefore, in a first step I execute an eigenvalue study and extract the system matrices, the eigenvalues and the (right) eigenvectors via the COMSOL LiveLink for Matlab using the functions mphmatrix and mphgetu. The model order reduction is then performed in a second step in Matlab. However, for the model order reduction the right AND left eigenvectors are required but only the right eigenvector can be extracted in a straightforward manner. So far, transposing the system matrices in Matlab and returning them to COMSOL via mphinputmatrix did the trick to get the left eigenvector. For systems with large numbers of degrees of freedom, however, the function mphinputmatrix fails due to limitations of the Java Heap Memory (OutOfMemoryError: Java heap space) in Matlab, although the Java heap space was already increased to a maximum value of 8GB. As the manipulation of the load vector is more convenient to do in Matlab, the reduced order model simulations are preferred to also being performed in Matlab.
Long story short: Is there any possibility to extract the left eigenvector calculated in COMSOL to Matlab? Do you have any other suggestions to solve that issue?
Any help is kindly appreciated.
Best regards, Gerrit
Hello Gerrit Heilmann
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