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Semialgebraic systems? http://www.singular.unikl.de/forum/viewtopic.php?f=10&t=2283 
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Author:  user [ Tue Sep 17, 2013 9:14 pm ] 
Post subject:  Semialgebraic systems? 
Is there any library able to solve semialgebraic polynomial systems? Or, at least, dealing with regular chains? Thanks. 
Author:  gorzel [ Fri Nov 08, 2013 2:42 pm ] 
Post subject:  Re: Semialgebraic systems? 
Singular offers no syntax to denote inequalities. So the answer is almost no, with the the exception of linear equations. This is, the simplex method is available: http://www.singular.unikl.de/Manual/la ... htm#SEC426 To answer the question in a wider range about real algebraic computations, Singular offers some libraries: realrad_lib for Computation of real radicals http://www.singular.unikl.de/Manual/la ... tm#SEC1336 Two libraries for Counting the number of real roots of uni and multivariate polynomial systems rootsur_lib http://www.singular.unikl.de/Manual/la ... tm#SEC1918 and rootsmr_lib http://www.singular.unikl.de/Manual/la ... tm#SEC1902 respectively. These implement: Descartes' rule of signs, the BudanFourier theorem, Sturm sequences and SturmHabicht sequences. The computation of the SturmHabicht sequences (subresultants) are imititated by Groebner basis calculations. Hence it does not perform as well as a proper implementation could do. (Although subresultants are implemented in the kernel of the factorization engines, these commands are not directly accessible to the user.) For those interested in usage of Groebner basis as a preprocces in semialgebraic computations, see for instance: David J. Wilson, Russell J. Bradford, James H. Davenport Speeding up Cylindrical Algebraic Decomposition by GrÃ¶bner Bases http://arxiv.org/abs/1205.6285 (Though, this work reports on calculations with Maple.) 
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