## ichudov@algebra.com (Igor Chudov)11 Jul 2005 07:03:35 -0400

From comp.compilers

Related articles
Re: Advanced expression simplification marcov@stack.nl (Marco van de Voort) (2005-07-11)
Re: Advanced expression simplification haberg@math.su.se (2005-07-12)
Re: Advanced expression simplification eugene.ressler@frontiernet.net (Gene) (2005-07-17)
Advanced expression simplification drikosv@otenet.gr (Evangelos Drikos) (2005-07-17)
Re: Advanced expression simplification liekweg@ipd.info.uni-karlsruhe.de (F. Liekweg) (2005-07-17)
| List of all articles for this month |

 From: ichudov@algebra.com (Igor Chudov) Newsgroups: comp.compilers Date: 11 Jul 2005 07:03:35 -0400 Organization: Compilers Central Keywords: optimize, code, question Posted-Date: 11 Jul 2005 07:03:35 EDT

I am writing an algebra expression simplifier. It parses an expression
and then applies various rules to the parsed tree. It also produces
"work shown". Much of it already works (reduction of constants,
similar terms, similar factors, etc). It works with expressions of
arbitrary complexity, powers etc.

http://www.algebra.com/services/rendering/simplifier.mpl

Now I am approaching more difficult areas.

Specifically, in simplification, some approaches can be tried and
abandoned. For example:

(x^2-1)/(x-1) simplifies to x+1. GOOD

(1^100-1)/(x-1) "simplifies" to x^99+x^98+...+x+1. NOT GOOD.

If I do such things, I need to make sure that simplification does not
loop with endless tries, and that it takes a reasonable amount of
time. Some approaches can initially lead to bigger expressions, and
then to smaller ones. The typical example is use of associative
property.

I cannot expect all simplification approaches to always reduce the
size of expressions. And yet, I need to know "where to stop".

Are there any good treatises on expression simplification.

thanks

i

--

Post a followup to this message