October 2004 - GiNaC-list

code: extended gcd
by Ralf Stephan 20 Nov '04

20 Nov '04

Hello, please include the following snippet. Its application domain depends on that of quo() which is univariate, currently. It is tested but not heavily so. It is not optimized. Thanks, ralf Input: x,y rational polynomials Computes u,v,d such that ux+vy = gcd(x,y). /////////// Extended GCD ex xgcd (const ex& a, const ex& b, ex& u, ex& v, const symbol& s) { const ex& x = a.normal(); const ex& y = b.normal(); if (is_exactly_a<numeric>(x) && is_exactly_a<numeric>(y) && x.info(info_flags::integer) && y.info(info_flags::integer)) { cln::cl_I cu, cv, cr; cr = cln::xgcd (cln::the<cln::cl_I>(ex_to<numeric>(x).to_cl_N()), cln::the<cln::cl_I>(ex_to<numeric>(y).to_cl_N()), &cu, &cv); u = numeric(cu); v = numeric(cv); return numeric(cr); } if (is_exactly_a<numeric>(y) && y.info(info_flags::integer)) { u = 0; v = numeric(1)/y; return 1; } if (is_exactly_a<numeric>(x) && x.info(info_flags::integer)) { v = 0; u = numeric(1)/x; return 1; } if (x.info(info_flags::rational_polynomial) && y.info(info_flags::rational_polynomial)) { ex d, p, q; d = gcd (x, y); int dx = degree(x, s), dy = degree(y, s); if (dx < dy) { p = y; q = x; } else { p = x; q = y; } ex u1,u2,u3,v1,v2,v3,w1,w2,w3; u1 = p; u2 = 1; u3 = 0; v1 = q; v2 = 0; v3 = 1; while (!v1.is_zero()) { ex Q = quo (u1, v1, s); w1 = u1 - Q*v1; w2 = u2 - Q*v2; w3 = u3 - Q*v3; u1 = v1.expand(); u2 = v2.expand(); u3 = v3.expand(); v1 = w1.expand(); v2 = w2.expand(); v3 = w3.expand(); } u = (u2 / ((u1/d).normal())).expand(); v = (u3 / ((u1/d).normal())).expand(); //cerr << "CHK: " << (u*x+v*y).expand() << endl << flush; return d; } throw invalid_argument("xgcd(): not a rational polynomial"); }

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GiNaC 1.3.0
by Jens Vollinga 14 Nov '04

14 Nov '04

Hi, GiNaC 1.3.0 is out and available. The changes are: - No funny announcements anymore. - The Clifford classes have been generalized to allow working with Clifford algebras generated by arbitrary symmetric tensors or matrices. Also, a lot of new functions for Clifford algebras have been added, including automorphisms and Moebius transformations. [Contribution by V. Kisil] - Added some basic symbolic and numeric integration facilities. [Contribution by C. Dams] - The multiple polylogarithm Li() now evaluates numerically for arbitrary arguments. - New functions G(a,y) and G(a,s,y) added (another notation for multiple polylogarithms). As always, this release can be downloaded from ftp://ftpthep.physik.uni-mainz.de/pub/GiNaC/ Enjoy, Jens

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An Example of Clifford Algebras Calculations with GiNaC
by Vladimir Kisil 19 Oct '04

19 Oct '04

Hi, I put at arXiv.org 'An Example of Clifford Algebras Calculations with GiNaC'. The link to paper is http://arxiv.org/abs/cs.MS/0410044 and abstract is given below. Best wishes, Vladimir -- Vladimir V. Kisil email: kisilv(a)maths.leeds.ac.uk -- www: http://maths.leeds.ac.uk/~kisilv/ ------------------------------------------------------------------------------ \\ Title: An Example of Clifford Algebras Calculations with GiNaC Authors: Vladimir V. Kisil Comments: 20 pages, LaTeX2e, 12 PS graphics in one figure Report-no: LEEDS-MATH-PURE-2004-18 Subj-class: Mathematical Software; Computational Geometry; Graphics; Symbolic Computation \\ This example of Clifford algebras calculations uses GiNaC (http://www.ginac.de/) library, which includes a support for generic Clifford algebra starting from version~1.3.0. Both symbolic and numeric calculation are possible and can be blended with other functions of GiNaC. This calculations was made for the paper math.CV/0410399. Due to course described features of GiNaC should propagate into other software like GNU Octave (http://www.octave.org/) and gTybalt (http://www.fis.unipr.it/~stefanw/gtybalt.html) which uses GiNaC library as a back-end. \\

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GiNaC 1.2.4
by Jens Vollinga 12 Oct '04

12 Oct '04

Hi, GiNaC 1.2.4 is out and available. The changes are: - Added ex::unitcontprim() to compute the unit, content, and primitive parts of a polynomial in one go. - binomial(n, k) evaluates for non-integer arguments n. - Li(2,x) now evaluates for +-I. - Optimized Li(2,x). - Fixed bug in Li(n,x) (if Li(2,x) was calculated with high precision the enlargement of the look-up table caused a segmentation fault). - Fixed another bug in the series expansion of powers, and a bug in power::info(). As always, this release can be downloaded from ftp://ftpthep.physik.uni-mainz.de/pub/GiNaC/ Enjoy, Jens

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bug in series expansion of powers
by varg＠thsun1.jinr.ru 06 Oct '04

06 Oct '04

Hello! This simple program #include <iostream> #include <ginac/ginac.h> using namespace std; using namespace GiNaC; int main(int argc, char** argv) { symbol x("x"); symbol a("a"); symbol b("b"); ex test = pow(x+a,b); cout << test << " = " << test.series(x,3) << endl; return 0; } gives (x+a)^b = 1+Order(x^3) instead of (x+a)^b = (a^b)+(a^b*b*a^(-1))*x+(1/2*a^b*b^2*a^(-2)-1/2*a^b*b*a^(-2))*x^2+Order(x^3) Attached patch fix this bug.

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GiNaC Application: Ecco
by Kai Ludwig 06 Oct '04

06 Oct '04

Hi Folks, thanks to the GiNaC library, we developped the kinetic facilities of Ecco - A Compiler for (Electro-)Chemistry. GiNaC enables the support of so called 'generic rate laws' that can be used to model any rate expression for the simulation of chemical and/or electrochemical reaction kinetics. Thanks to you all!! Kai -- http://echempp.sourceforge.net Kai Ludwig Institut für Organische Chemie Auf der Morgenstelle 18 72076 Tübingen Tel.: 07071/29-73049 Mail: kai.ludwig(a)uni-tuebingen.de

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patch: put ginac.pc into libginac-dev
by varg＠thsun1.jinr.ru 06 Oct '04

06 Oct '04

Hello! This small patch slightly changes packaging rules to get ginac.pc included into libginac-dev. Best regards, Alexei.

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var list
by Ralf Stephan 05 Oct '04

05 Oct '04

This must be a faq: Is there a function that returns a lst of all variables in an ex? Or, what's wrong with the following (which leaves symbols empty)? class CollectSymbols_Visitor : public visitor, public symbol::visitor { public: lst symbols; CollectSymbols_Visitor() {} void visit (const symbol& x) { for (lst::const_iterator i = symbols.begin(); i != symbols.end(); i++) if (*i == x) return; symbols.append(x); } }; int main() { symbol x("x"); ex e = x - 2; CollectSymbols_Visitor collector; e.accept (collector); const lst& sym = collector.symbols; cout << sym << endl; }

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