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Equal indexed expressions
by Vladimir Kisil 26 Apr '05

26 Apr '05

Hi, I am wondering how to convince GiNaC that the following to expressions are equal: [[-1,0],[0,1]~mu~mu * a~mu [[-1,0],[0,1].nu~mu * a~nu Thanks for an advice, Vladimir -- Vladimir V. Kisil email: kisilv(a)maths.leeds.ac.uk -- www: http://maths.leeds.ac.uk/~kisilv/

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Two remarks.
by Chris Dams 22 Apr '05

22 Apr '05

Dear GiNaCers, (1) Once upon a time, not even that long ago, it was possible to browse the GiNaC CVS by clicking on "CVS tree" on the homepage. At the moment this gives the text: "/home/cvs not found! The server on which the CVS tree lives is probably down. Please try again in a few minutes." (2) Could somebody explain why there is a non-trivial method idx::match_same_type? This method makes it impossible to match varidx(mu,4-delta) using the pattern varidx(wild(1),wild(2)), which could be useful sometimes. Best wishes, Chris

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simplify_indexed and inheritance
by mdias＠ift.unesp.br 21 Mar '05

21 Mar '05

Hi guys, I have a simple question. I would like to construct a derived class of indexed type, folowing the final part of tutorial. How can I inherit simplify_indexed()? For example: class Myclass : public indexed{ .... } Myclass(ex b, idx a), indexed(b,a) { ... } Myclass::simplify_indexed() { I don't know!!! } Thanks in advance, Marco ------------------------------------------------- This mail sent through IMP: http://horde.org/imp/

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Ginac and scilab
by Galassi Luca 11 Mar '05

11 Mar '05

Hello, I'am a student that i need to implement inside scilab a symbolic derivative. I see that the ginac library implements what i need. But I don't know if anyone have already implement this function inside scilab.If not, please,can you help me to create an unique object ginac.o to load better your library inside Scilab?I've tried to edit the makefile, but I don't understand a lot of that. Thank you in advance. Luca Galassi

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let_op() and index
by mdias＠ift.unesp.br 01 Mar '05

01 Mar '05

Hi guys, Wrinting the code below I can define op() function, but I cant define let_op() (I now, it seems to be a very simple problem...) #include <iostream> #include <ginac/ginac.h> using namespace std; using namespace GiNaC; class covdiff : public indexed{ GINAC_DECLARE_REGISTERED_CLASS(covdiff,indexed) public: idx index; ex arg; covdiff(const ex, idx) ; ex & let_op(size_t i); size_t nops() const; } ex covdiff::op(size_t i) const { switch (i){ case 0: return arg; case 1: return index; default: throw std::range_error("covdiff::op(): no such operand"); } } ex & covdiff::let_op(size_t i) { ensure_if_modifiable(); switch (i){ case 0: return arg; case 1: return index; <--------error occur here default: throw std::range_error("covdiff::op(): no such operand"); } } test.cpp: In member function `virtual GiNaC::ex& covdiff::let_op(unsigned int) ': test.cpp:88: error: invalid initialization of reference of type 'GiNaC::ex&' from expression of type 'GiNaC::idx' Thanks, Marco ------------------------------------------------- This mail sent through IMP: http://horde.org/imp/

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indexed structure, is possible???
by mdias＠ift.unesp.br 22 Feb '05

22 Feb '05

Hi, I am working in a kind of covariant derivative. I started with a structure, like in page 81 of tutorial: covdiff(argument,index) I implemented distributive, Leibniz rule, etc.. But I would like to make GiNac threat this structure like a indexed object ( metric tensor could rise indexes, etc). Is there a function option in the definition of structure or a TINFO option? Thanks for all Marco ------------------------------------------------- This mail sent through IMP: http://horde.org/imp/

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Mixed index simmetry
by mdias＠ift.unesp.br 21 Feb '05

21 Feb '05

Hi, I am new in Ginac,and have a stupid question. I dont know how to get all possible permutations of the four index pairs (sigma, l), (mu,m), (nu,n) and (rho,o). (Its a QCD vertex...) in the expression: ex four = color_f(a,b,c)*color_f(a,d,e)*(delta_tensor(l,b)*delta_tensor(m,c)*d elta_tensor(n,d)*delta_tensor(o,e)*metric_tensor(alpha,sigma)*metric_tensor(beta ,mu)*metric_tensor(nu,alpha.toggle_variance())*metric_tensor(beta.toggle_varianc e(),rho): I can make somethink like four.symmetrize((sigma,l),(mu,m),(nu,n),(rho,o))? I've looked at the archives and didn t find. Thanks a lot, Marco ------------------------------------------------- This mail sent through IMP: http://horde.org/imp/

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ginac ./configure doesn't find CLN installation...
by Kim Lux 13 Feb '05

13 Feb '05

$./configure ... an error occured: checking for cln-config... /usr/local/bin/cln-config checking for CLN - version >= 1.1.0... no *** Could not run CLN test program, checking why... *** The test program compiled, but did not run. This usually means *** that the run-time linker is not finding CLN or finding the wrong *** version of CLN. If it is not finding CLN, you'll need to set your *** LD_LIBRARY_PATH environment variable, or edit /etc/ld.so.conf to point *** to the installed location. Also, make sure you have run ldconfig if that *** is required on your system. ... So... cd /usr/local/bin $ ls cln-config ... $./cln-config --version 1.1.9 $ ./cln-config --libs -L/usr/local/lib -lcln -lgmp $ ./cln-config --cppflags -I/usr/local/include $ ./cln-config --exec-prefix /usr/local $ echo $LD_LIBRARY_PATH <nothing> What do I do to make configure work ? -- Kim Lux, Diesel Research Inc.

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Integration
by Jason Dusek 08 Feb '05

08 Feb '05

Hi, I read that someone has recently added symbolic integration to GiNaC. Can it do this integrand: (x - 1)/(x*sqrt(x^3 + 1) or q / ||r|| dV ? Is it good enough for use, or should I wait a bit? -- _jason

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Fwd: Performance problem with series
by Frieder Kalisch 03 Feb '05

03 Feb '05

Hi, here is a very odd performance behaviour of ginac/series: The operation ex e = 1/(a+sqrt(b*b+x*x)); e = e.series(x==1, 21); is more than a factor of 10^4(!) faster then outputting the result using cout << e << endl; I have measured these times using clocks(). You find the source of the program at the end of this email. What does this mean? This means, that series is very efficient (both time- and space-wise), because it reuses intermediate results heavily. On the other hand the result is nearly useless, because it is actually _very_ complicated, which shows up in any subsequent usage. In this specific example, a hand-written taylor-series using derivatives was 2 orders of magnitude slower (for 60th order) to compute the series, but the series (20th order) still was printed 1000 times faster than the standard series. In the light of this finding, something needs to be done. I suggest to essentially revert the logic of series, namely to compute series by differentiation and to fall back to an explicit composition if it does not work. Mathematica does it that way according to its documentation. At least ginac should provide this mode as an option, either by an additional taylor() method for ex or by means of series_options. Do You agree with this analysis and my conclusions? Are there any other ways to solve this problem? Regards Frieder Kalisch #include <ginac/ginac.h> #include <iostream> #include <ctime> using namespace GiNaC; using namespace std; int main(int argc, char **argv) { time_t t0, t1, t2; t0 = clock(); symbol x("x"), a("a"), b("b"); ex e = 1/(a+sqrt(b*b+x*x)); e = e.series(x==1, 21); t1 = clock(); cout << e << endl; t2 = clock(); double res = CLOCKS_PER_SEC; cerr << (t1-t0)/res << endl << (t2-t1)/res << endl; return 0; } // int main(int argc, char **argv) -- Frieder Kalisch Institut für theoretische Physik kalisch(a)tphys.uni-heidelberg.de Philosophenweg 19 +49-6221-549-433 D-69120 Heidelberg

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