Re: using ublas to solve linear systems?

From: deane_yang (Deane_Yang_at_[hidden])
Date: 2002-11-12 09:09:23

Thanks for the helpful reply! I just have a few more comments and questions.

> > For example, why is B on both sides of the assignment operator?
> > Does this imply that "B = solve(A,B, tag)" causes B to be
> > replaced by A^{-1}B?
> 
> Oops. I've just looked into the sources (always recommended ;-) and 
noticed
> that this is a documentation bug. The corrected documentation should read
> 
> C = solve(A, B, tag)   <------>      C <- A^-1 B
> 
> Corresponding inplace "solvers" are used internally:
> 
> inplace_solve(A, B, ...)   <------>      B <- A^-1 B
> 
> Maybe I should add an appropriate dispatcher function and document it, 
too.

I'm not sure what this means, but having the in-place solver available publicly
sounds like a good idea.

> 
> > And is it standard lingo in some circles to say
> > "solve for a triangular matrix" for the act of replacing a vector
> > or matrix B by A^{-1}B, where A is triangular? I find this odd,
> > since when I say "solve for <something>", I mean that <something>
> > is an unknown object that needs to be found through a calculation.
> 
> Sorry, I'm not a native speaker. How would you correct this?
> 

This is, I admit, a little tricky. The best I can come up with is
"solve a triangular system of equations" or "invert a triangular matrix".

Deane