#
eigs

**eigs**,
a Fortran90 code which
calculates the eigenvalues of a real matrix.

In cases like MATLAB, Octave, and Python, there is a standard
built-in function for computing eigenvalues which is appropriate
for this task, and we simply supply a code eigs_test() to demonstrate
its use.

In other cases, particularly C, C++, Fortran77 and Fortran90,
pre-existing eigenvalue software has been rearranged and packaged
to form a simple function of the form eigs(n,A,lambda), which
saves the user from the usual trouble of arranging a proper call.

Here, the Fortran90 version of eigs() relies on a call to the lapack()
function dgeev() to produce its results. It is assumed that a
precompiled copy of the lapack() library is available at link time.

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Licensing:

The information on this web page is distributed under the MIT license.

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Languages:

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Related Data and Programs:

eigs_test

arpack,
a Fortran90 code which
uses Arnoldi iteration to compute eigenvalues for large matrices.
It includes a reverse communication (RC) feature.
It is Richard Lehoucq, Danny Sorensen, Chao Yang;

eispack,
a Fortran90 code which
carries out eigenvalue computations.
It includes a function to compute the singular value decomposition (SVD)
of a rectangular matrix.
superseded by lapack();

jacobi_eigenvalue,
a Fortran90 code which
implements the Jacobi iteration for the iterative determination
of the eigenvalues and eigenvectors of a real symmetric matrix.

lapack_test,
a Fortran90 code which
calls lapack(), which
is a standard linear algebra package for solving linear systems,
computing matrix factorizations, and solving eigenvalue problems.
A precompiled copy of the lapack() library is often available
on most scientific computing systems.

power_method,
a Fortran90 code which
carries out the power method for finding a dominant eigenvalue
and its eigenvector.

test_eigen,
a Fortran90 code which
defines various eigenvalue test cases.

test_matrix,
a Fortran90 code which
defines test matrices, some of
which have known eigenvalues and eigenvectors.

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Source Code:

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Last revised on 05 June 2024.
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