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Advertisement for GiNaC
by Chris Dams 19 Jul '05

19 Jul '05

Dear developers, At the moment I am finishing my PhD-thesis. The interesting thing about the promotion regulations at my university is that it allows PhD-theses to contain two pages for advertisement. I thought it was a good idea to spend such a page on the greatest computer algebra library that I know. So, you have an opportunity to get some free publicity ;-). You can find the page on http://www.theorphys.science.ru.nl/people/dams/ginacpage.ps . My questions: do you have a vector image of the logo? Do you have some other suggestions for the text? Now I have just cutted and pasted the text of the webpage. Best wishes, Chris

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Re: [GiNaC-list] Question
by Vladimir V. Kisil 18 Jul '05

18 Jul '05

Hi, >>>>> "JRG" == Javier Ros Ganuza <jros(a)unavarra.es> writes: JRG> I want to do algebra with cartesian (3x1) "vectors". Cartesian JRG> "vector"s are to be represented by a 3x1 Ginac vector (3-tuple) JRG> and a reference to a basis that tell us in which base the JRG> components have physical sense. Extension of GiNaC classes is not very difficult and you may implement from scratch. However it may be better to do this through the Clifford algebras in GiNaC. There are many references (e.g. books of Hestenes) on doing geometry with Clifford algebras. JRG> for example (in my particular jargon): JRG> vector1.expresion=matrix(3,1,lst(a1,b1,c1)); JRG> vector1.basis=basis_k; JRG> vector2.expresion=matrix(3,1,lst(a2,b2,c2)); JRG> vector1.basis=basis_l; This can be implemented as follows: varidx nu(symbol("nu", "\\nu"), 3), mu(symbol("mu", "\\mu"), 3); xi(symbol("xi", "\\xi"), 3), rho(symbol("rho", "\\rho"),3); basis1 = clifford_unit(mu, diag_matrix(lst(1, 1, 1))); basis2 = clifford_unit(nu, diag_matrix(lst(1, 1, 1))); vector1 = lst_to_clifford(lst(a1,b1,c1), xi, basis1); vector2 = lst_to_clifford(lst(a1,b1,c1), rho, basis2); Then the expression JRG> result=2*vector1+vector2; will be well defined and behave as expected even without reduction to the single basis. The reduction is needed only if someone try to extract its components in either basis1, basis2, or even another basis3. To this end values of all products like basis1[i]*basis2[j] (i.e. transition matrix) should be defined. Best wishes, Vladimir -- Vladimir V. Kisil email: kisilv(a)maths.leeds.ac.uk -- www: http://maths.leeds.ac.uk/~kisilv/

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Re: GiNaC 1.3.1
by Chris Dams 13 Jul '05

13 Jul '05

Dear Jens, You wrote: > - Fixed a library initialization problem. Why do you think so? The safety suggested by the library_init class is still nothing more than a sham. Best wishes, Chris

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matrix::solve(): how to use?
by mdias＠ift.unesp.br 12 Jul '05

12 Jul '05

Hi guys, I am tryng to solve a linear system with lsove(), with many variables being zero, so lsolve() tell that is indeterminate, but some of these entries are of interest. So, I am looking for matrix::solve and construct a matrix to solve this. Somebody have a piece of code how to make a linear system a matrix to matrix::solve ? Thanks, Marco

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GiNaC 1.3.2 release
by Jens Vollinga 11 Jul '05

11 Jul '05

Hi, GiNaC 1.3.2 is out and available. The changes are: - GCD avoids to produce expanded expressions. - Fixed bug in expanding expressions containing dummy indices. - Fixed static initialization order bug. - collect_common_factors now works with powers. - Modernized configuration scripts. Thanks to all the contributers, especially C.Dams, V.Kisil and A.Sheplyakov. As always, this release can be downloaded from ftp://ftpthep.physik.uni-mainz.de/pub/GiNaC/ Enjoy, Jens Vollinga

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[PATCH] small improvements of gcd and collect_common_factors
by varg＠theor.jinr.ru 08 Jul '05

08 Jul '05

Hello! collect_common_factors does not work with powers, e.g. (in ginsh) > collect_common_factors((a*x+a*y)^2); (a*x+a*y)^2 I don't like such a behaviour, so I made the patch. With that patch, the above code actually works: > collect_common_factors((a*x+a*y)^2); a^2*(y+x)^2 To guarantee mathematical correctness, this transformation is applied to polynomial expressions only: > collect_common_factors((a*x+a*y)^n); (a*x+a*y)^n Apart from collect_common_factors hack, this patch somewhat improves worst-case performance of gcd and sr_gcd. Best regards, Alexei -- ROOT: an octopus made by nailing extra legs onto a cat.

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[PATCH] build system: wipe deprecated autoconf macros
by varg＠theor.jinr.ru 30 Jun '05

30 Jun '05

Hello! This patch removes [some of the] obsolete autoconf macros, so auto* things do not complain any more. It also removes the `autogen.sh' script, since its job can be done with a simple autoreconf -i command (in fact, according to autoconf documentation, this is the recommended way to bootstrap a project). Best regards, Alexei -- ROOT: an octopus made by nailing extra legs onto a cat.

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lsolve
by mdias＠ift.unesp.br 28 Jun '05

28 Jun '05

Hi guys, I am tring to solve a system (in my tests) like that: 16*Fv==16*k*p-32*m^2+16*k^2+32*p*p1 -16*Ga==0 -24*Fm*m^2-24*Fm*p*p1==0 2*m^2*Fs+2*p*Fs*p1==32*m*k*p+32*m^3+64*m*p*p1 8*m^2*Gp+8*p*Gp*p1==0 8*m^2*Ge-8*Ge*p*p1==0 {Fv==Fv,Ga==Ga,Fm==Fm,Fs==Fs,Gp==Gp,Ge==Ge} I think Ga==0, Fv== (...)/16 , etc. How to instruct lsolve only to solve nonzero elements? Thanks in advance, Marco A. F. Dias

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Vector algebra from Clifford units
by Vladimir Kisil 24 Jun '05

24 Jun '05

Hi, In response to the previous request on vector algebra in different bases I include a simple illustration how to achieve principal vector operations from the Clifford algebra functionality in GiNaC. This is working with current CVS but will not work yet with the current release 1.3.1. Hope this can be useful, Vladimir -- Vladimir V. Kisil email: kisilv(a)maths.leeds.ac.uk -- www: http://maths.leeds.ac.uk/~kisilv/ #include <ginac/ginac.h> using namespace std; using namespace GiNaC; ex vector3D(const ex & list, const ex & basis, const ex & mu) { varidx nu((new symbol)->setflag(status_flags::dynallocated), 3); return indexed(matrix(1, 3, ex_to<lst>(list)), nu.toggle_variance())*basis.subs(mu == nu); } ex scalar_product(const ex & v1, const ex & v2) { return remove_dirac_ONE(canonicalize_clifford(expand_dummy_sum((v1*v2 + v2*v1)/2))); } ex vector_product(const ex & v1, const ex & v2, const ex & e_prod) { return canonicalize_clifford(expand_dummy_sum((v1*v2 - v2*v1)*e_prod/2)); } int main(){ realsymbol a1("a1"), b1("b1"), c1("c1"), a2("a2"), b2("b2"), c2("c2"), a3("a3"), b3("b3"), c3("c3"), t("t"); varidx nu(symbol("nu", "\\nu"), 3), mu(symbol("mu", "\\mu"), 3); ex M = diag_matrix(lst(1, 1, 1)), // Metrics of point spaces T = matrix (3, 3, lst(0, 0, 1, 0, 1, 0, -1, 0, 0)),// Transformation matrix basis1 = clifford_unit(mu, M, 0), // Main basis defined by Clifford units basis2 = basis1 * indexed(T, nu, mu.toggle_variance()), // Transformed basis e1_prod = basis1.subs(mu == 0)*basis1.subs(mu == 1)*basis1.subs(mu == 2), // Maps bivecors to vectors vect1 = vector3D(lst(a1, b1, c1), basis1, mu), // vector in the main basis vect2 = vector3D(lst(a2, b2, c2), basis2, nu), // vector in the transformed basis vect3 = vector3D(lst(a3, b3, c3), basis1, mu); // second vector in the main basis cout << canonicalize_clifford(expand_dummy_sum(2*vect1+t*vect2)) << endl; //-> -e~0*c2*t+a2*t*e~2+2*a1*e~0+2*c1*e~2+e~1*b2*t+2*b1*e~1 cout << clifford_to_lst(2*vect1+t*vect2, basis1) << endl; //-> {-c2*t+2*a1,b2*t+2*b1,2*c1+a2*t} cout << scalar_product(vect1, vect3) << endl; //-> b3*b1+c1*c3+a3*a1 cout << scalar_product(vect1, vect2) << endl; //-> a2*c1+b1*b2-a1*c2 cout << vector_product(vect1, vect3, e1_prod) << endl; //-> a3*b1*e~2-c1*a3*e~1+c1*b3*e~0-b1*e~0*c3+a1*e~1*c3-b3*a1*e~2 cout << clifford_to_lst(vector_product(vect1, vect3, e1_prod), basis1) << endl; //-> {-b1*c3+c1*b3,a1*c3-c1*a3,-b3*a1+a3*b1} cout << vector_product(vect1, vect2, e1_prod) << endl; //-> c1*e~1*c2+a2*a1*e~1-a1*b2*e~2-a2*b1*e~0+c1*e~0*b2-b1*c2*e~2 cout << clifford_to_lst(vector_product(vect1, vect2, e1_prod), basis1) << endl; //-> {c1*b2-a2*b1,c1*c2+a2*a1,-b1*c2-a1*b2} }

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ginsh as a subroutine?
by John Fletcher 23 Jun '05

23 Jun '05

I would like to be able to call a subroutine with a string e.g. "x+y" and receive back an ex object containing the expression and also a map mapping "x" and "y" strings to symbol objects. The example program ginsh does this internally. I think it could be added within the class for ex objects. Has anyone done this? Thanks John -- Dr John P. Fletcher Tel: (44) 121 204 3389 (direct line) Chemical Engineering and Applied Chemistry (CEAC), School of Engineering and Applied Science (SEAS), Aston University, Aston Triangle, BIRMINGHAM B4 7ET U.K. CEAC Web site http://www.ceac.aston.ac.uk/ FAX: (44) 121 204 3679

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