Albert Rich schrieb: > > On Friday, June 20, 2014 9:38:45 PM UTC-10, clicl...@freenet.de wrote: > > > The Rubi 4.5 Utility Functions exhibit a typo in the error message > > "Warning: Unrecogized expression for expansion". > > > > I saw a handful of TimeConstraineds in this file, some evidently used > > to tame MMA's Simplify. But you also use this brutal means to protect > > the recursive FixSimplify rule set as well as the recursive functions > > NormalizeSumFactors and ContentFactorAux, all of which seem entirely > > under your control. Why is this necessary? Does Rubi have to be > > prevented from getting lost in the woods of its integration rules in > > this way too? > > > > PS: Another misprint: The integral sign is missing for Example 5 in > > Chapter 7 of Timofeev's integrals, as found on the Rubi website: > > Thank you for reporting the two typos. They have been corrected and > revised versions of the files posted on Rubi's website. > > Unfortunately as a last resort on integrands it does not recognize, > Rubi sometimes uses integration methods, like partial fraction > expansion, that can hang the system. Also the simplification of > recursively derived integrands can hang the system. Therefore, Rubi > uses the TimeConstrained function to regain control after a fixed, > somewhat arbitrary amount of time. Elimination of such hacks depends > on finding rules that clearly result in simpler integrands -- a never > ending and fascinating quest... >
Hmmm. How about checking the number of unevaluated Ints in your expression at some critical junctions and aborting when a preset limit is exceeded? Integrand leaf counts may also be considered.
Integration Example #75 from Chapter 5 of the Timofeev Test Suite ran into a 25-second timeout on Version 4.4. Does Rubi 4.5 resurface eventually, and what is the final result, or error message?
I am curious how far Rubi 4.5 allows one to go with Martin's integrals: