July 2016 - GiNaC-devel

Toggling index covariance in simplify_indexed()
by Vladimir V. Kisil 12 Aug '16

12 Aug '16

Dear All, I am confused by the following. The routine simplify_indexed() calls reposition_dummy_indices(), which has the freedom to toggle dummy indices covariance to achieve canonical order. Leaving aside the question "does the position of an index have geometrical/physical significance and can be harmlessly toggled?", I come to the following unpredictability of the GiNaC output in the different runs of the same compiled programme: #include <ginac/ginac.h> #include <fstream> using namespace std; using namespace GiNaC; int main(){ realsymbol x("x"), y("y"); varidx mu(symbol("mu", "\\mu"), 2); ex e = clifford_unit(mu, diag_matrix(lst{-1,-1})); ex V = lst_to_clifford(lst{x,y}, e); cout << V << endl; // -> e~mu*[[x],[y]].mu cout << simplify_indexed(V) << endl; // in different runs can be either // (A) -> e~mu*[[x],[y]].mu (as above) or // (B) -> e.mu*[[x],[y]]~mu cout << canonicalize_clifford(V*V) << endl; // depanding on the above outcomes: // (A) -> (e~mu*e~symbol6)*[[x],[y]].symbol6*[[x],[y]].mu // (B) -> -2*ONE*y^2-[[x],[y]]~symbol6*[[x],[y]]~mu*(e.symbol6*e.mu)-2*x^2*ONE cout << canonicalize_clifford(simplify_indexed(V)*simplify_indexed(V)) << endl; // (A) -> (e~mu*e~symbol10)*[[x],[y]].mu*[[x],[y]].symbol10 // (B) -> -(e~symbol13*e~mu)*[[x],[y]].mu*[[x],[y]].symbol13-2*ONE*y^2-2*x^2*ONE cout << canonicalize_clifford(simplify_indexed(V)*V) << endl; // (A) -> -[[x],[y]]~symbol14*(e.symbol14*e~mu)*[[x],[y]].mu-2*ONE*y^2-2*x^2*ONE // (B) -> -2*ONE*y^2-[[x],[y]]~mu*[[x],[y]]~symbol20*(e.symbol20*e.mu)-2*x^2*ONE cout << canonicalize_clifford(expand_dummy_sum(simplify_indexed(V)*V)) << endl; // (A) -> -y^2*ONE-x^2*ONE // (B) -> y^2*(e.1*e~1)+x^2*(e.0*e~0)+x*y*(e.0*e~1)-x*y*(e~0*e.1) return 0; } Any advice on usability/necessity of this behaviour? Best wishes, Vladimir -- Vladimir V. Kisil http://www.maths.leeds.ac.uk/~kisilv/ Book: Geometry of Mobius Transformations http://goo.gl/EaG2Vu Software: Geometry of cycles http://moebinv.sourceforge.net/

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[SCM] GiNaC -- a C++ library for symbolic computations branch, master, updated. release_1-4-0-564-g33a92d5
by git＠ginac.de 21 Jul '16

21 Jul '16

This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GiNaC -- a C++ library for symbolic computations". The branch, master has been updated via 33a92d56aeaadfe8dad246ae17b091e14b220e82 (commit) from 55d29b0d5bad410574358f54bf0f760d0cc79ae7 (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- commit 33a92d56aeaadfe8dad246ae17b091e14b220e82 Author: Richard Kreckel <kreckel(a)ginac.de> Date: Thu Jul 21 08:55:44 2016 +0200 [bugfix] Fix crash in basic::subs(). A regression in 1.7.0 was introduced with 1b8bcb06 in function basic::subs_one_level(): implicitly casting *this to an ex first for finding *this in m and later in the function's return statement caused a crash in the second cast because *this was deleted in the first one. After all, *this was dynamically allocated in basic::subs(). This bug was reported and hunted down by Mario Prausa. ----------------------------------------------------------------------- Summary of changes: ginac/basic.cpp | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) hooks/post-receive -- GiNaC -- a C++ library for symbolic computations

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is_a<function>: C++11 compiler issue?
by Vladimir V. Kisil 10 Jul '16

10 Jul '16

Dear All, I am trying to compile the following code: #include <ginac/ginac.h> using namespace GiNaC; using namespace std; int main () { symbol x("x"); ex a=exp(x); cout << is_a<symbol>(x) << endl; cout << is_a<function>(a) << endl; } If a compiler option -std=gnu++11 is used, I got errors like this: test-g.cpp:9:26: error: no matching function for call to 'is_a(GiNaC::ex&)' cout << is_a<function>(a) << endl; (see the full log at the end of my message). Compiler complains about is_a<symbol> but is happy with is_a<function>(a). The code can be compiled and run well if -std=gnu++11 is omitted. Any suggestions? Best wishes, Vladimir -- Vladimir V. Kisil http://www.maths.leeds.ac.uk/~kisilv/ Book: Geometry of Mobius Transformations http://goo.gl/EaG2Vu Software: Geometry of cycles http://moebinv.sourceforge.net/ ===================================================================== test-g.cpp: In function 'int main()': test-g.cpp:9:10: error: parse error in template argument list cout << is_a<function>(a) << endl; ^ test-g.cpp:9:26: error: no matching function for call to 'is_a(GiNaC::ex&)' cout << is_a<function>(a) << endl; ^ In file included from /usr/include/ginac/registrar.h:27:0, from /usr/include/ginac/basic.h:29, from /usr/include/ginac/ginac.h:28, from test-g.cpp:1: /usr/include/ginac/print.h:181:13: note: candidate: template<class T> bool GiNaC::is_a(const GiNaC::print_context&) inline bool is_a(const print_context & obj) ^ /usr/include/ginac/print.h:181:13: note: template argument deduction/substitution failed: test-g.cpp:9:26: error: template argument 1 is invalid cout << is_a<function>(a) << endl; ^ In file included from /usr/include/ginac/ginac.h:28:0, from test-g.cpp:1: /usr/include/ginac/basic.h:311:13: note: candidate: template<class T> bool GiNaC::is_a(const GiNaC::basic&) inline bool is_a(const basic &obj) ^ /usr/include/ginac/basic.h:311:13: note: template argument deduction/substitution failed: test-g.cpp:9:26: error: template argument 1 is invalid cout << is_a<function>(a) << endl; ^ In file included from /usr/include/ginac/ginac.h:30:0, from test-g.cpp:1: /usr/include/ginac/ex.h:930:13: note: candidate: template<class T> bool GiNaC::is_a(const GiNaC::ex&) inline bool is_a(const ex &obj) ^ /usr/include/ginac/ex.h:930:13: note: template argument deduction/substitution failed: test-g.cpp:9:26: error: template argument 1 is invalid cout << is_a<function>(a) << endl; ^

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