December 2008 Archives

Matrix Eigenvalues in Perl Don't Get Much Easier

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The Matrix subsystem has really grown up in the last few days since the 0.16 release, including easy-to-use methods to calculate Matrix eigenvalues. All kinds of other methods are now available, like
my $det1 = $A->det;      # determinant
my $det2 = abs $A;       # determinant

my $inv = $A->inverse;  
my @eigs = $A->eigenvalues;

my ($eigenvalues, $eigenvectors) = $matrix->eigenpair;
my ($eig1,$eig2) = @$eigenvalues;
my ($u,$v)       = @$eigenvectors;
Compare this new script for calculating eigenvalues and eigenvectors of a nonsymmetric matrix to the old version. Yes, quite an improvement and quite pleasing to the eye now. Note that $A->eigenvalues; returns a list of Math::Complex objects because in general the eigenvalues of a real matrix can be complex. Only if your matrix is symmetric are you guaranteed real eigenvalues.
I just pushed Math::GSL 0.16 to CPAN, it should be showing up here Real Soon Now, depending on how much traffic the dump trucks hit on the intertubes

  • Fixed RT#40947: configure_requires ExtUtils::PkgConfig bug
  • Operator overloading for addition, multiplication and subtraction on Matrix objects (Thierry)
  • Fix an include bug in Histogram2D which caused the build to fail (Thierry)
  • Added reverse() and swap() methods to VectorComplex objects with tests and docs
  • as_list() and get() now work on VectorComplex objects
    • as_list() returns a list of Math::Complex objects
    • get() returns a list of Math::GSL::Complex objects
  • Math::GSL::Test::ok_status() now takes an optional message argument
  • Added KNOWN_BUGS
  • Added Math::GSL::Test::is_status_ok()
  • New subsytems: VectorComplex and MatrixComplex
  • Operator overloading for addition and subtraction with vectors
  • Added example: examples/matrix/nonsymmetric_eigen
    • Shows how to find the eigenvalues of a nonsymmetric matrix
  • Added copy() method to vectors
  • Improved Vector docs
  • Sped up vector dot products by 15x using BLAS function gsl_blas_ddot
    • NOTE: using gsl_blas_ddot($x->raw,$y->raw) directly is still about 10 times faster than $x * $y due to error checking and function call overhead
  • Separated POD and Perl code out of SWIG interface files, yay for proper syntax highlighting
  • Added stub test files for Heapsort, IEEEUtils, Multimin, Siman, Wavelet2D
  • All test files now keep track of how many tests should run

Back on track

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I haven't been able to add code to Math::GSL since about a month because of a tricky bug I had with the build process. Not only was it tricky, it was well hidden and pretty stupid to fix once I saw it.

Now that it's fixed I've been able to commit some code concerning overloading operators + and - in Math::GSL::Matrix. It's been tested and documented but it could still enjoy more documentation. End term exams are coming pretty fast to me so I won't finish overloading multiplication of matrices before one or two weeks.

Ho and Math::GSL 0.16 should be out soon, stay tuned!

Math::GSL 0.15_05

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I just pushed Math::GSL 0.15_05 to CPAN, which includes these fixes since 0.15_04 : 

  • Fixed RT#40947: configure_requires ExtUtils::PkgConfig bug 
  • Added reverse() method to VectorComplex objects with tests and docs 
  • as_list() and get() now work on VectorComplex objects 
    • as_list() returns a list of Math::Complex objects 
    • get() returns a list of Math::GSL::Complex objects


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