Re: [eigen] Thank you for creating Eigen!

Hi Alexander,

That is wonderful to hear! I would just like to point you to the Eigen Tensor module, which (at least for Eigen 3.3) supports a variety of tensor operations. It actually forms the computational basis for Google's opensource TensorFlow project, and we are a few people in the TensorFlow team helping to develop/maintain it, including the main author Benoit Steiner.

Take a look at the (not complete) documentation here:

https://bitbucket.org/eigen/eigen/src/c313894d14ea4aea129ffe82ad9c1cfec844c0dd/unsupported/Eigen/CXX11/src/Tensor/?at=default

The main interfaces are defined here:

https://bitbucket.org/eigen/eigen/src/c313894d14ea4aea129ffe82ad9c1cfec844c0dd/unsupported/Eigen/CXX11/src/Tensor/TensorBase.h?at=default&fileviewer=file-view-default

The unit tests here provide some usage examples:

https://bitbucket.org/eigen/eigen/src/c313894d14ea4aea129ffe82ad9c1cfec844c0dd/unsupported/test/?at=default

On Wed, Oct 19, 2016 at 3:57 AM, Alexander Voigt <alexander.voigt@xxxxxxxxxxxxxxxxxxxxxx> wrote:

Dear Eigen developers,

herewith I'd like to thank you very much creating the incredibly fast
and versatile Eigen package!

I am a physicist working in theoretical particle physics and I'm using
Eigen for one of my projects: FlexibleSUSY [1]. FlexibleSUSY is a
spectrum generator, a program that calculates the masses of elementary
particles in a very wide class of particle physics models.

For calculating the particle masses with high precision, one challenge
is to being able to calculate extremely complex matrix expressions
very efficiently (the so-called beta-functions [2]). These matrix
expressions are so complicated that they usually span multiple pages
and they need to be evaluated tens of thousands of times. Using
Eigen, we are able to evaluate these complicated expressions in an
incredibly short time, which gives us a big speed improvement over
other spectrum generators (SARAH/SPheno [3], SOFTSUSY [4]) and a high
speed is a premiss to study particle physics models at the LHC
experiment. Interestingly, the evaluation of the matrix expressions
in C++ using the Eigen library is much faster than the classic matrix
multiplication in Fortran (using Fortran's MatMul() function).

Best regards,
Alexander Voigt

P.S.: One Eigen feature which we're looking forward to is rank-3 and
-4 tensors, which appear in some extended particle physics models.
Thus, we cannot easily handle such models for now due to the missing
support of rank-3 and -4 tensors in Eigen 3.2.

P.P.S.: If you think FlexibleSUSY is relevant enough, I'd be happy if
it could be added to the list of "Projects using Eigen" in the section
"Science".

[1] https://flexiblesusy.hepforge.org
https://github.com/FlexibleSUSY
arXiv:1406.2319, arXiv:1609.00371
[2] arxiv:hep-ph/9311340, arxiv:1107.2670, arxiv:1310.7629
[3] http://sarah.hepforge.org/
[4] http://softsusy.hepforge.org/

--
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Dr. Alexander Voigt
Institute for Theoretical Particle Physics and Cosmology
RWTH Aachen
Sommerfeldstr. 14
52074 Aachen
Room: 28A408
Phone: +49 (0)241 80 27049
Fax : +49 (0)241 80 22187
E-Mail: alexander.voigt@xxxxxxxxxxx-aachen.de
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