December 2021 - GiNaC-list

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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