- GiNaC-list - ginac.de

GiNaC 1.8.4 released
by Richard B. Kreckel 19 Sep '22

19 Sep '22

Hi, GiNaC 1.8.4 has been tagged and released with some unplanned git noise. The News: * Complete the support for sqrfree_parfrac(). * Add info methods for transcendental functions. -richy. -- Richard B. Kreckel <https://in.terlu.de/~kreckel/>

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Potential issue in comparator in test_antipode
by Yuri Gribov 06 Jun '22

06 Jun '22

Hi, The comparison in `node::operator<` in time_antipode.cpp seems to be missing a dereference operation in return statement: if (!(*vert==*n.vert)) return (vert<n.vert); This causes the comparator to be non-transitive: (gdb) p *keys[5] < *keys[4] $5 = true (gdb) p *keys[4] < *keys[8] $6 = true (gdb) p *keys[5] < *keys[8] $7 = false which violates the strict weak ordering requirements of std::map (https://en.cppreference.com/w/cpp/named_req/Compare) Such violations may in practice result in non-deterministic behavior or crashes. The issue was found with [SortChecker++ tool](https://github.com/yugr/sortcheckxx). Best regards, Yuri Gribov

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GiNaC 1.8.3 released
by Richard B. Kreckel 24 Mar '22

24 Mar '22

Hi, GiNaC 1.8.3 has been tagged. The News: * series_to_poly() can be used from ginsh. * Fix power::to_polynomial() for posint exponents. * Fix power::subs() in some special cases. As always, happy hacking, and a lovely UN International Day for the Right to the Truth Concerning Gross Human Rights Violations and for the Dignity of Victims! (24 March) -richy. -- Richard B. Kreckel <https://in.terlu.de/~kreckel/>

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a counterintuitive case with subs
by Feng Feng 23 Mar '22

23 Mar '22

Dear all, I got a problem with the function subs, and I am not sure it is a possible bug or not, but it seems counterintuitive. Here is the code to reproduce the case: //------------------------------------------------ #include "ginac/ginac.h" using namespace std; using namespace GiNaC; int main() { symbol s("s"); ex t = subs(1/s,s==1/s, subs_options::no_pattern); cout << t << endl; return 0; } //------------------------------------------------ The output is 1/s instead of s. PS: if I remove the subs_options::no_pattern, the output is s as expected. and I have a look at the source code of basic::subs, it seems it comes from the following code: that is, the final substitutions on the new object as a whole, //------------------------------------------------ // Perform substitutions on the new object as a whole return copy->subs_one_level(m, options); //------------------------------------------------ Thanks very much in advance. Best regards! Feng

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Add series_to_poly to ginsh
by Vitaly Magerya 07 Feb '22

07 Feb '22

Hi, all. Could we add "series_to_poly" to ginsh? It would make operating on series easier; as it stands there's no way to discard the Order() term in ginsh. The patch is attached (does this list accept attachments?).

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factorization bug
by Ivan Vasilyev 05 Feb '22

05 Feb '22

Hi! I believe there's an intermittent bug in GiNaC::factor() function. Sometimes it leaves uncancelled terms with seemingly random coefficients like: w*(w^2*(K^4*B^2+B^2-2*K^2*B^2)+196*w^2*K^4+196*w^2+C^2-196*w^2*(1+K^4-2*K^2)-392*w^2*K^2)*A The minimal code to reproduce the bug in GiNaC 1.8.2 is: #include <ginac/ginac.h> #include <iostream> int main() { std::string input("w^3*B^2*A-2*w^3*K^2*B^2*A+w*C^2*A+w^3*K^4*B^2*A"); while (true) { std::ostringstream s; GiNaC::parser reader; s << factor(reader(input)); if (s.str().length() <= input.length()) continue; std::cout << s.str() << '\n'; return 0; } } Also, this problem can be reproduced on https://daninet.github.io/ginac-wasm/ with the same expression being calculated several times in a row: factor(w^3*B^2*A-2*w^3*K^2*B^2*A+w*C^2*A+w^3*K^4*B^2*A); With best regards, Ivan.

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Re: [GiNaC-list] to_polynomial function does not return a polynomial
by Feng Feng 14 Jan '22

14 Jan '22

Dear Vladimir, Thanks so much for checking this, and thanks for the quick update on the git! Best regards! Feng 在 2022年1月13日 22:35，Vladimir V. Kisil<V.Kisil(a)leeds.ac.uk> 写道： Dear Feng, Thanks for spotting this typo. Indeed currently the following lines symbol x("x"); ex a = pow(x+1/x,2); cout << a << endl; exmap mp1, mp2; ex p = a.to_polynomial(mp1); cout << " = " << p << "\n with " << mp1 << endl; p = a.expand().to_polynomial(mp2); cout << " = " << p << "\n with " << mp2 << endl; produce the output with not a polynomial in the first instance: (x^(-1)+x)^2 = (x^(-1)+x)^2 with {} = 2+symbol3^2+x^2 with {symbol3==x^(-1)} If to_rational() is replaced by to_polynomial() as you suggested, then we do have (although slightly different) polynomial outputs in both cases: (x+x^(-1))^2 = (x+symbol3)^2 with {symbol3==x^(-1)} = 2+x^2+symbol4^2 with {symbol4==x^(-1)} I am attaching a one-line patch to fix this and copy the message to the developer list. Best wishes, Vladimir -- Vladimir V. Kisil http://www.maths.leeds.ac.uk/~kisilv/ Book: Geometry of Mobius Maps https://doi.org/10.1142/p835 Soft: Geometry of cycles http://moebinv.sourceforge.net/ Jupyter notebooks: https://github.com/vvkisil?tab=repositories >>>>> On Tue, 11 Jan 2022 07:10:40 +0000, Feng Feng <f.feng(a)outlook.com> said: FF> Dear Vladimir V. Kisil, FF> Thanks very much for suggestion to use expand() method on e3 FF> first. FF> And I have given a look at the source code at FF> power::to_polynomial FF> https://www.ginac.de/reference/normal_8cpp_source.html#l02688 FF> ... FF> and I wonfer if there is a typo on line 2691, the FF> basis.to_rational can be replaced with basis.to_polynomial? FF> Best regards! Feng

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Re: [GiNaC-list] to_polynomial function does not return a polynomial
by Feng Feng 13 Jan '22

13 Jan '22

Dear Vladimir V. Kisil, Thanks very much for suggestion to use expand() method on e3 first. And I have given a look at the source code at power::to_polynomial https://www.ginac.de/reference/normal_8cpp_source.html#l02688 2688 ex power::to_polynomial(exmap & repl) const 2689 { 2690 if (exponent.info(info_flags::posint)) 2691 return pow(basis.to_rational(repl), exponent); 2692 else if (exponent.info(info_flags::negint)) 2693 { 2694 ex basis_pref = collect_common_factors(basis); 2695 if (is_exactly_a<mul>(basis_pref) || is_exactly_a<power>(basis_pref)) { 2696 // (A*B)^n will be automagically transformed to A^n*B^n 2697 ex t = pow(basis_pref, exponent); 2698 return t.to_polynomial(repl); 2699 } 2700 else 2701 return pow(replace_with_symbol(pow(basis, _ex_1), repl), -exponent); 2702 } 2703 else 2704 return replace_with_symbol(*this, repl); 2705 } and I wonfer if there is a typo on line 2691, the basis.to_rational can be replaced with basis.to_polynomial? Best regards! Feng

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GiNaC 1.8.2 released
by Richard B. Kreckel 01 Jan '22

01 Jan '22

Happy New Year! GiNaC 1.8.2 has just been released. Here's what's new: * Fix elusive bug in comparing relational objects. * Ensure modular_form_kernel::series() includes an Order term. Happy hacking! -richy. -- Richard B. Kreckel <https://in.terlu.de/~kreckel/>

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to_polynomial function does not return a polynomial
by Feng Feng 28 Dec '21

28 Dec '21

Dear all, I am using the function to_polynomial to produce a polynomial from a expression, it seems that to_polynomial does not return a polynomial in some cases, as illustrated in the following example, note that it works well on expression e2, while it does nothing on e3 (e3=e2^2), and does not return a polynomial. #include "ginac/GiNaC.h" using namespace GiNaC; using namespace std; int main() { symbol x("x"), y("y"); auto e1 = x+y; auto e2 = e1+1/e1+pow(e1,4); auto e3 = pow(e2, 2); exmap mp2; ex p2 = e2.to_polynomial(mp2); cout << " = " << p2 << "\n with " << mp2 << endl; //= y+symbol4+x+(y+x)^4 // with {symbol4==(y+x)^(-1)} exmap mp3; ex p3 = e3.to_polynomial(mp3); cout << " = " << p3 << "\n with " << mp3 << endl; //= (y+(y+x)^(-1)+x+(y+x)^4)^2 //with {} return 0; } Best regards! Feng

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