April 2024 - GiNaC-list

bugs in indexed object
by Dr. Mithun Bairagi 14 Apr '24

14 Apr '24

Dear all ginac lovers, I have found simplify_indexed() is not working as expected. I have compiled and run the following c++ program using ginac 1.87 (mingw64 compiler, windows 10 os), #include <ginac/ginac.h> using namespace GiNaC; using namespace std; int main() { symbol A("A"), B("B"), C("C"), i_sym("i"),j_sym("j"); varidx i(i_sym, 3); varidx ic(i_sym, 3,true); varidx j(j_sym, 3); varidx jc(j_sym, 3,true); ex e = indexed(A, {i,i}) * indexed(B, {ic,ic})-indexed(A, {j,j}) * indexed(B, {jc,jc}); cout << (e).simplify_indexed() << endl; return 0; } the above program shows the following result: A.i.i*B~symbol16.symbol16-A.i.i*B~symbol17.symbol17 But I think the result should be zero. Please tell me what is the problem here? Best regards, Mithun Bairagi

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GPL v2 and v3 compatibility issues
by Diddens, Christian (UT-TNW) 13 Apr '24

13 Apr '24

Dear GiNaC team, first of all, thanks so much for your powerful projects GiNaC and CLN! Thanks so much for making them open to us all! Based on your projects (and others), I have developed a nice multi-physics finite element framework, which I would like to share with the world soon. Of course, I will also go for the GPL, but I get conflicts, since I also have another dependency (pygmsh) using GPL v3, which is not compatible with GPL v2 of GiNaC and CLN. I total, I have to satisfy BSD-3-Clause, BSD-2-Clause, MIT, LGPL-2.1-only, LGPL-2.1-or-later, GPL-2.0-or-later, GPL-2.0-only and GPL-3.0-only. This configuration is not compatible under any outbound licence, unless I leave out either the GPL-2.0-only dependencies (GiNaC & CLN) or the GPL-3.0-only dependency (pygmsh). Of course, I have read your statement in the FAQ: ---- I don't like the GPL. May I have another license, please? A: The idea to dual-license GiNaC has been proposed a number of times. It has, however, been squarely rejected by some developers. Asking for a permission to dual-license it is likely going to waste your valuable time. That being said: The GPL is a good license. Why not directly put derived work under the GPL, too? ---- I am not asking for a dual-license, I support the ideas of the GPL myself, but I just wonder whether there are any plans to go for GPL-2.0-or-later at any time? If not, I have to get rid of the GPL-3.0 dependency, i.e. write my own interface to gmsh, before I can publish my work under GPL-2.0-only as well. Thanks for any information, help or suggestions in this issue! Best regards, Christian

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bug in ex::ex(const std::string&, const ex&)
by Diego Conti 05 Apr '24

05 Apr '24

Hi, I think there is a bug in the functions that convert strings to ex. I attach a minimal program that segfaults on my machine. I am using gcc 13.2.0 on Ubuntu 23.10, x86_64, CPU Intel i9-12900H. The problem only arises if I compile GiNaC using the CMake script. The same program works if I compile with configure && make. The problem appears to be in parser/default_reader.cpp, where conversions between pointers to functions and integers are used. The code assumes that the integer underlylng a pointer to function is even, relying on the fact that functions are aligned; this latter condition appears to fail on my system when compiling with CMake. Indeed, inserting a pragma command inside parser/default_reader.cpp (see attached patch) fixes the problem. I do not know if this can be made portable across compilers; maybe it would be easier to modify the code by replacing reader_func with a class that handles the conversion in a type-safe way? Diego Conti

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