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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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Re: [GiNaC-list] A strange behaviour while implementing archive in auser-defined class
by Feng Feng 20 Dec '21

20 Dec '21

Thanks very much for the patch! And again thanks a lot for the suggestions for Symbol::calchash, that is really what I am looking for! Best regards! Feng 在 2021年12月20日 16:57，Oleg Finkelshteyn<olegfink(a)gmail.com> 写道： i suspect this is actually due to a typo in relational::compare_same_type. (basic reality check: pathologic (e.g. constant) hash functions should lead to degraded performance, not different results) diff --git a/ginac/relational.cpp b/ginac/relational.cpp index 599a2635..dbc541a3 100644 --- a/ginac/relational.cpp +++ b/ginac/relational.cpp @@ -223,8 +223,8 @@ int relational::compare_same_type(const basic & other) const return (o < oth.o) ? -1 : 1; break; } - const int lcmpval = lh.compare(oth.rh); - return (lcmpval!=0) ? lcmpval : rh.compare(oth.lh); + const int lcmpval = lh.compare(oth.lh); + return (lcmpval!=0) ? lcmpval : rh.compare(oth.rh); } attached is also a shorter test along the same lines as Feng's. it prints the result of comparing two symbol==0 expressions to each other both ways. without the patch, the output is -1 -1 (which is inconsistent), and with the patch it's -1 1. a hash collision is needed to elicit this bug because basic::compare returns early without calling compare_same_type if hashes differ. Feng: regardless of this bug, i think you'll want something like following: unsigned Symbol::calchash() const { hashvalue = get_symbol(get_name()).gethash(); setflag(status_flags::hash_calculated); return hashvalue; } thanks On Sat, 18 Dec 2021, at 11:10, Vladimir V. Kisil wrote: >>>>>> On Sat, 18 Dec 2021 16:22:22 +0800, Feng Feng <f.feng(a)outlook.com> said: > FF> I got a strange behaviour while implementing the archive in > FF> user-defined class, to make the behaviour more explicitly, let > > If you will delete the method Symbol::calchash() from your class you > will get the expected behaviour. > -- > 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 Sat, 18 Dec 2021 16:22:22 +0800, Feng Feng <f.feng(a)outlook.com> said: > > FF> Dear all, > > > FF> I got a strange behaviour while implementing the archive in > FF> user-defined class, to make the behaviour more explicitly, let > FF> me post the C++ code here: > > > FF> #include <ginac/ginac.h> #include <fstream> > > > FF> using namespace GiNaC; using namespace std; > > > FF> class Symbol : public symbol { > FF> GINAC_DECLARE_REGISTERED_CLASS(Symbol, symbol) public: > FF> Symbol(const string &s); void archive(archive_node & n) const > FF> override; void read_archive(const archive_node& n, lst& sym_lst) > FF> override; unsigned calchash() const override; }; > FF> GINAC_DECLARE_UNARCHIVER(Symbol); > > > FF> GINAC_IMPLEMENT_REGISTERED_CLASS(Symbol, symbol) > FF> GINAC_BIND_UNARCHIVER(Symbol); > > > FF> const symbol & get_symbol(const string & s) { static map<string, > FF> symbol> dict; if (dict.find(s) == dict.end()) dict[s] = > FF> symbol(s); return dict[s]; } > > > FF> Symbol::Symbol() { } Symbol::Symbol(const string &s) : > FF> symbol(get_symbol(s)) { } int Symbol::compare_same_type(const > FF> basic &other) const { const Symbol &o = static_cast<const Symbol > FF> &>(other); int ret = get_name().compare(o.get_name()); > FF> if(ret==0) return 0; else if(ret<0) return -1; else return 1; } > > FF> void Symbol::archive(archive_node & n) const { > FF> inherited::archive(n); } > > FF> void Symbol::read_archive(const archive_node& n, lst& sym_lst) { > FF> inherited::read_archive(n, sym_lst); *this = Symbol(get_name()); > FF> } > > > FF> unsigned Symbol::calchash() const { static auto hash = > FF> symbol("_").gethash(); return hash; } > > > FF> int main() { Symbol k1("k1"), k2("k2"); auto garfn = "tmp.gar"; > > FF> { archive ar; ex val = lst{ k1*k1, k2*k2 }; > FF> ar.archive_ex(val, "key"); ofstream out(garfn); out << ar; > FF> out.close(); cout << "writed: " << val << endl; } { archive ar; > FF> ifstream in(garfn); in >> ar; in.close(); auto val = > FF> ar.unarchive_ex(lst{}, "key"); cout << "read: " << val << endl; > FF> } // console output is // writed: {k1^2,k2^2} // read: > FF> {k1^2,k2^2} > > FF> { archive ar; ex val = lst{ k1*k1==0, k2*k2==0 }; > FF> ar.archive_ex(val, "key"); ofstream out(garfn); out << ar; > FF> out.close(); cout << "writed: " << val << endl; } { archive ar; > FF> ifstream in(garfn); in >> ar; in.close(); auto val = > FF> ar.unarchive_ex(lst{}, "key"); cout << "read: " << val << endl; > FF> } // console output is // writed: {k1^2==0,k2^2==0} // read: > FF> {k1^2==0,k1^2==0} // Note that the last line above, both items > FF> are the same: k1^2==0 > > FF> return 0; } > > > FF> Here I want to introduce a class Symbol, when one defines Symbol > FF> a(“a”), b(“a”);, then a and b will be the same or equal, so I > FF> override the method compare_same_type. > > > > > FF> The last console output seems very strange to me, the both items > FF> are the same, while the expected result is "read: > FF> {k1^2==0,k2^2==0}”. > > > FF> Thanks very much! > > > FF> Best regards! Feng > > FF> ---------------------------------------------------- > FF> Alternatives: > > FF> ---------------------------------------------------- > FF> _______________________________________________ GiNaC-list > FF> mailing list GiNaC-list(a)ginac.de > FF> https://www.ginac.de/mailman/listinfo/ginac-list > _______________________________________________ > GiNaC-list mailing list > GiNaC-list(a)ginac.de > https://www.ginac.de/mailman/listinfo/ginac-list

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A strange behaviour while implementing archive in a user-defined class
by Feng Feng 20 Dec '21

20 Dec '21

Dear all, I got a strange behaviour while implementing the archive in user-defined class, to make the behaviour more explicitly, let me post the C++ code here: #include <ginac/ginac.h> #include <fstream> using namespace GiNaC; using namespace std; class Symbol : public symbol { GINAC_DECLARE_REGISTERED_CLASS(Symbol, symbol) public: Symbol(const string &s); void archive(archive_node & n) const override; void read_archive(const archive_node& n, lst& sym_lst) override; unsigned calchash() const override; }; GINAC_DECLARE_UNARCHIVER(Symbol); GINAC_IMPLEMENT_REGISTERED_CLASS(Symbol, symbol) GINAC_BIND_UNARCHIVER(Symbol); const symbol & get_symbol(const string & s) { static map<string, symbol> dict; if (dict.find(s) == dict.end()) dict[s] = symbol(s); return dict[s]; } Symbol::Symbol() { } Symbol::Symbol(const string &s) : symbol(get_symbol(s)) { } int Symbol::compare_same_type(const basic &other) const { const Symbol &o = static_cast<const Symbol &>(other); int ret = get_name().compare(o.get_name()); if(ret==0) return 0; else if(ret<0) return -1; else return 1; } void Symbol::archive(archive_node & n) const { inherited::archive(n); } void Symbol::read_archive(const archive_node& n, lst& sym_lst) { inherited::read_archive(n, sym_lst); *this = Symbol(get_name()); } unsigned Symbol::calchash() const { static auto hash = symbol("_").gethash(); return hash; } int main() { Symbol k1("k1"), k2("k2"); auto garfn = "tmp.gar"; { archive ar; ex val = lst{ k1*k1, k2*k2 }; ar.archive_ex(val, "key"); ofstream out(garfn); out << ar; out.close(); cout << "writed: " << val << endl; } { archive ar; ifstream in(garfn); in >> ar; in.close(); auto val = ar.unarchive_ex(lst{}, "key"); cout << "read: " << val << endl; } // console output is // writed: {k1^2,k2^2} // read: {k1^2,k2^2} { archive ar; ex val = lst{ k1*k1==0, k2*k2==0 }; ar.archive_ex(val, "key"); ofstream out(garfn); out << ar; out.close(); cout << "writed: " << val << endl; } { archive ar; ifstream in(garfn); in >> ar; in.close(); auto val = ar.unarchive_ex(lst{}, "key"); cout << "read: " << val << endl; } // console output is // writed: {k1^2==0,k2^2==0} // read: {k1^2==0,k1^2==0} // Note that the last line above, both items are the same: k1^2==0 return 0; } Here I want to introduce a class Symbol, when one defines Symbol a(“a”), b(“a”);, then a and b will be the same or equal, so I override the method compare_same_type. The last console output seems very strange to me, the both items are the same, while the expected result is "read: {k1^2==0,k2^2==0}”. Thanks very much! Best regards! Feng

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Re: [GiNaC-list] A strange behaviour while implementing archive in auser-defined class
by Feng Feng 18 Dec '21

18 Dec '21

Dear Vladimir, Thanks very much for the quick reply! Indeed, when I remove the calchash method, I get the expected result. So when writting to an archive, GiNaC will use the hash internally, and I still have a question, why does the first console output give the result: "read: {k1^2,k2^2}”? Thanks again! Best regards! Feng 在 2021年12月18日 19:10，Vladimir V. Kisil<V.Kisil(a)leeds.ac.uk> 写道： >>>>> On Sat, 18 Dec 2021 16:22:22 +0800, Feng Feng <f.feng(a)outlook.com> said: FF> I got a strange behaviour while implementing the archive in FF> user-defined class, to make the behaviour more explicitly, let If you will delete the method Symbol::calchash() from your class you will get the expected behaviour. -- 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 Sat, 18 Dec 2021 16:22:22 +0800, Feng Feng <f.feng(a)outlook.com> said: FF> Dear all, FF> I got a strange behaviour while implementing the archive in FF> user-defined class, to make the behaviour more explicitly, let FF> me post the C++ code here: FF> #include <ginac/ginac.h> #include <fstream> FF> using namespace GiNaC; using namespace std; FF> class Symbol : public symbol { FF> GINAC_DECLARE_REGISTERED_CLASS(Symbol, symbol) public: FF> Symbol(const string &s); void archive(archive_node & n) const FF> override; void read_archive(const archive_node& n, lst& sym_lst) FF> override; unsigned calchash() const override; }; FF> GINAC_DECLARE_UNARCHIVER(Symbol); FF> GINAC_IMPLEMENT_REGISTERED_CLASS(Symbol, symbol) FF> GINAC_BIND_UNARCHIVER(Symbol); FF> const symbol & get_symbol(const string & s) { static map<string, FF> symbol> dict; if (dict.find(s) == dict.end()) dict[s] = FF> symbol(s); return dict[s]; } FF> Symbol::Symbol() { } Symbol::Symbol(const string &s) : FF> symbol(get_symbol(s)) { } int Symbol::compare_same_type(const FF> basic &other) const { const Symbol &o = static_cast<const Symbol FF> &>(other); int ret = get_name().compare(o.get_name()); FF> if(ret==0) return 0; else if(ret<0) return -1; else return 1; } FF> void Symbol::archive(archive_node & n) const { FF> inherited::archive(n); } FF> void Symbol::read_archive(const archive_node& n, lst& sym_lst) { FF> inherited::read_archive(n, sym_lst); *this = Symbol(get_name()); FF> } FF> unsigned Symbol::calchash() const { static auto hash = FF> symbol("_").gethash(); return hash; } FF> int main() { Symbol k1("k1"), k2("k2"); auto garfn = "tmp.gar"; FF> { archive ar; ex val = lst{ k1*k1, k2*k2 }; FF> ar.archive_ex(val, "key"); ofstream out(garfn); out << ar; FF> out.close(); cout << "writed: " << val << endl; } { archive ar; FF> ifstream in(garfn); in >> ar; in.close(); auto val = FF> ar.unarchive_ex(lst{}, "key"); cout << "read: " << val << endl; FF> } // console output is // writed: {k1^2,k2^2} // read: FF> {k1^2,k2^2} FF> { archive ar; ex val = lst{ k1*k1==0, k2*k2==0 }; FF> ar.archive_ex(val, "key"); ofstream out(garfn); out << ar; FF> out.close(); cout << "writed: " << val << endl; } { archive ar; FF> ifstream in(garfn); in >> ar; in.close(); auto val = FF> ar.unarchive_ex(lst{}, "key"); cout << "read: " << val << endl; FF> } // console output is // writed: {k1^2==0,k2^2==0} // read: FF> {k1^2==0,k1^2==0} // Note that the last line above, both items FF> are the same: k1^2==0 FF> return 0; } FF> Here I want to introduce a class Symbol, when one defines Symbol FF> a(“a”), b(“a”);, then a and b will be the same or equal, so I FF> override the method compare_same_type. FF> The last console output seems very strange to me, the both items FF> are the same, while the expected result is "read: FF> {k1^2==0,k2^2==0}”. FF> Thanks very much! FF> Best regards! Feng FF> ---------------------------------------------------- FF> Alternatives: FF> ---------------------------------------------------- FF> _______________________________________________ GiNaC-list FF> mailing list GiNaC-list(a)ginac.de FF> https://www.ginac.de/mailman/listinfo/ginac-list

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Substitution and re-evaluation
by Gregor Kälin 10 Nov '21

10 Nov '21

Hi, I'm extending GiNaC by some new classes and ran into a problem with subs and eval. My class, representing an integral, inherits from basic and is essentially a container class containing several ex's itself. The subs method, inherited from basic, works as expected for the substitution step, but does not re-evaluate the expression (i.e. the eval function of my class is not called after the substitution happened). The tutorial states "All GiNaC methods that transform expressions, like subs() or normal(), automatically re-evaluate their results." and, hence, I would expect that the default subs method of the basic class calls eval somewhere in the process. Is this a bug in basic::subs or am I supposed to take care of a re-evaluation of my custom classes myself (i.e. essentially overriding subs and calling eval explicitly in the process)? Looking into the source code (I'm on commit 9197695fc, ginac version 1.8.1-1) I'd expect a call to eval on line 628 of basic.cpp after all operands have been substituted, and before subs_one_level is called. Best, Gregor

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GiNaC on the web
by Dani Biró 03 Nov '21

03 Nov '21

Hey GiNaC people! First of all, thank you for this great library! I'm working on a web-based interface for GiNaC as a hobby project and I wanted to share it with you. You can try a demo frontend here: https://daninet.github.io/ginac-wasm/ Source code: https://github.com/Daninet/ginac-wasm There is no operator overloading in JavaScript, so I had to implement functions like add(), mul() for the different operations. The GiNaC commands are batched for faster processing because WASM <=> JavaScript calls are too expensive. The demo frontend includes a PEG-based parser written in JavaScript, but the embedded parser is also exposed through the parse() function. At this moment, the JavaScript/TypeScript API looks like this: const GiNaC = await initGiNaC('./dist/ginac.wasm'); const g = getFactory(); GiNaC(g.mul(g.numeric('2'), g.pow(g.symbol('x'), g.numeric('2')))); GiNaC(g.series(g.atan(g.symbol('x')), g.symbol('x'), g.numeric('5'))); On my computer, the native ginsh is about 10x faster in estimating Pi with Machin’s formula compared to my WebAssembly port. That's because of the expensive C++ exception mocks generated by Emscripten, which compensate for the lack of native browser support for exceptions in WebAssembly. I estimate that the performance gap can be brought down to about 1/2 of native performance once the native exception instructions are getting wildly available in browsers. I plan to publish it on NPM (the JavaScript package library) when I manage to stabilize the API and implement the remaining features. What do you think? Do you have any suggestions or ideas? Best regards, Dani Biró

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