Re: Simplifying complicated expressions

*To*: mathgroup at smc.vnet.net*Subject*: [mg110452] Re: Simplifying complicated expressions*From*: Harrie Kraai <hakraai at xs4all.nl>*Date*: Sat, 19 Jun 2010 07:47:08 -0400 (EDT)*References*: <hudci1$d68$1@smc.vnet.net>

I asked a similar question about a year ago, http://groups.google.com/group/comp.soft-sys.math.mathematica/msg/a95d4651a5634771 and got this as the best answer: http://groups.google.com/group/comp.soft-sys.math.mathematica/msg/7cca617e1b4928c6 leading me to Experimental`OptimizeExpression But, also look at http://www.wolfram.com/technology/guide/CommonSubexpressionDetectionCollection/ perhaps Mathematica is doing something behind the scenes already. Harrie S. B. Gray wrote: > Suppose I have a long complex expression in which terms like > (x^2+y^3-x^2y^2+Sqrt[z3+y2]) (for a simple example) appear many times > along with various powers and the reciprocals of it, etc. To make the > expression comprehensible and to make the computation faster, I would > like to substitute say "f1xyz" for it everywhere it appears. The normal > /. and -> substitutions and patterns are not adequate for this. Of > course at evaluation time I want to compute f1xyz only once and not have > the final formula revert to the original variables. How do I prevent that? > > Also a welcome addition to Mathematica would be the ability to find these > repeated expressions automatically and put them in, because doing it > manually is very error-prone and slow. > > Tips will be appreciated! > > Steve Gray > >