Re: [eigen] EigenLab: C++ run-time matrix math ala MATLAB.

[Ilja Honkonen <ilja.j.honkonen@xxxxxxxx>]

Hello
On 31/8/14, 10:18, Marcel Goldschen wrote:
> Hi all,
> I've created a header only library called
> EigenLab (https://github.com/marcel-goldschen-ohm/EigenLab
> <https://github.com/marcel-goldschen-ohm/EigenLab>) which provides
> run-time parsing/evaluation of matrix math expressions in C++ with a
....
> what you think. Also, if anyone knows how I could improve its
> performance by using Eigen's expression templates, I'd love to hear
> about it.

I finally had time to try it out and it seems quite nice except it's 
very slow compared to muparserx. Parsing a simple expression (i + 1) 1e6 
times on my laptop takes about 0.07 s with muparserx and 4.7 s with 
EigenLab using these test programs:
https://github.com/nasailja/pamhd/blob/master/tests/eigenlab/performance1.cpp
https://github.com/nasailja/pamhd/blob/master/tests/muparserx/performance1.cpp

The muparserx test only has to parse the expression once, would it be 
possible to do a similar optimization in eigenlab if the expression 
doesn't change but only the value(s) of variable(s)?

Also it would be nice to have a better error message for using a wrong 
index [v1(1) instead of v1(0)] in an expression than: Assertion failed: 
(a_startRow >= 0 && blockRows >= 0 && a_startRow <= xpr.rows() - 
blockRows && a_startCol >= 0 && blockCols >= 0 && a_startCol <= 
xpr.cols() - blockCols), function Block, file 
/Users/iljah/libraries/eigen/Eigen/src/Core/Block.h, line 146. This is 
far less important than performance though as currently I don't think I 
could use eigenlab in my program because even muparserx takes a few seconds.

Ilja