[Ktechlab-devel] Slowmatrix! =)

[P Zoltan]

On Wed, 08 Jul 2009 08:12:43 +0200, Alan Grimes <agrimes at speakeasy.net>  
wrote:

> Okay, Zoltan, you've taken an interest in my matrix and vector classes,
> now it's time for your final exam. =P
>
> I'm too lazy to do this myself, (actually, I urgently need to spend more
> time earning money!!!),

  Do that then, but try to keep with your email up to date ;)

> but here's the idea take the interface to class
> Matrix (the LU solver) and implement a simple Gauss-jordan matrix
> inverter and call it "slowmatrix" (don't change the class name so that
> the alternate implementation can be compiled based on how the source is
> configured). You will be graded based on how efficient your overall
> approach to implementing each of the interface functions is and how well
> you take advantage of the functionality in QuickMatrix to shave cycles
> off of an inherently slow algorithm. =P
>
> Naturally, this alternate version must permit ktechlab to operate
> normally. (this is also an exam of your ability to research gauss-jordan
> elimination and implement it correctly.)
>

  As I mentioned before, I'd like to take a different approach: use the  
Eigen library instead of custom impelementation. That won't have strange  
bugs. I want to test it and probably use it to validate the current LU  
implementation, by using a fuzzy tehnique. If Eigen is fast enough, I'd  
prefer to keep using it in ktechlab.

  About the fuzzy testing: generate a matrix and a vector with random  
elements; apply LU to them by our impelementation and also by Eigen. Then  
compare the two; in another step solve the equation Ax=b, compare the  
result again; if the error is too great, we have a bug and a testcase for  
that bug.

  About configuration options: we could provide multiple Matrix  
impelmenations this way, by using the preprocessor defines and setting  
those using configure.

  The first thing I want to do is to find the minimal interface for the  
Matrix class used by the rest of the program.

  Opinions, suggestions?