- GiNaC-list - ginac.de

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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Include Guards
by Jason Dusek 22 Jan '05

22 Jan '05

In the FAQ, they discuss a problem with multiple inclusions of a header where global symbols are defined: ================================================ Q: I have various modules, some global variables and... A: ...and you are getting weird results with symbols not being identical? Imagine this situation: A file globals.h declares symbol x("x"). Two other modules #include "globals.h", do something with symbol x and return an expression ex containing the symbol to the caller (e.g. to main()). When the caller combines the two expressions there are really two different symbols both with the same print-name x. This may cause terms like x-x to stay around which will never be simplified to 0 because the system has no knowledge that the two symbols are supposed to be the same. How should it? After all the declarations really happend in different compilation units! ================================================ Can include guards solve this problem? Do I *have* to make that evil factory initializer thingy? -- _jason

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pyginac: numeric vs. ex and a failing test case
by Matti Peltomäki 17 Jan '05

17 Jan '05

Hi, Although being mostly about PyGiNaC I send this message on this list since the problem itself has also to do with GiNaC and may be interesting. I've been playing around with PyGiNaC and I accidentally found out, that running bin/check_matricies.py sometimes shows a failing test case, which looks like below (the test case seems to be the same as the one in GiNaC's check/check_matrices.cpp with the same name) -- snip -- Running __main__.funny_matrix_determinants.__doc__ Trying: funny_matrix_determinants() Expecting: 'Funny' matrix determinant test passed. ***************************************************************** Failure in example: funny_matrix_determinants() from line #1 of __main__.funny_matrix_determinants Expected: 'Funny' matrix determinant test passed. Got: Determinant of 5 x 5 matrix [[0,25/9+100/81*a,0,-24/35-6/5*c,24/35+6/5*c],[-5/4*c**(-1)*a*(c+3*a)*(b+a),0,2,0,-5/4*c**(-1)*a*(c+3*a)*(b+a)],[8*b**3*(2.7182818284590452354+1/2*c)*a**(-1),8/49*c*a**(-1),0,0,8*b**3*(2.7182818284590452354+1/2*c)*a**(-1)],[0,0,0,c**(-1)*b**2,-c**(-1)*b**2],[0,0,c*b**(-2),0,0]] was not found to vanish! 'Funny' matrix determinant test failed. -- snip -- I traced this back to sparse_tree() generating sometimes (sub)expressions of the form cos(1), i.e. a function with an argument of type numeric. Trying this out gives >>> from ginac import *; >>> cos(numeric(1)) <cginac.numeric object at 0xb7dda4f4> >>> print cos(numeric(1)) 0.5403023058681397174 >>> so that numerically evaluating the cosine leads to truncation errors and the determinant is no more exactly zero. Now, this evaluation seems to be exactly what GiNaC does if a numeric is given as a parameter to a function. OTOH, if the parameter is an ex, no evaluation occurs, even if the exs wraps a numeric. The following code #include <iostream> #include <ginac/ginac.h> using namespace GiNaC; using namespace std; int main(void) { cout << cos(numeric(1)) << endl; cout << cos(ex(numeric(1))) << endl; return 0; } gives 0.5403023058681397174 cos(1) This does not cause the same failure in the GiNaC test case since sparse_tree returns an ex. However, in PyGiNaC the return value is unwrapped from ex to whatever type it is, and with a numeric, the problem above occurs. So, in the end, I'm left with the situation that I don't know how to symbolically present something like cos(1) in PyGiNaC. Is it possible in some way not obvious to me? Best regards, Matti -- Matti Peltomaki, Undergraduate Research Assistant Laboratory of Physics Helsinki University of Technology 040 7576977, room Y308B

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Python bindings to GiNaC
by Ondrej Certik 13 Jan '05

13 Jan '05

Hello all, I wrote new Python bindings to ginac, because PyGiNaC (http://cens.ioc.ee/projects/pyginac/) seems to be dead and I wasn't able to even compile it. Currently I only support classes: basic, symbol, numeric, ex. But more can be done quite easily, unfortunately I probably won't have time to continue on it. More info at: http://ondrej.certik.cz/pyginac.php Does anyone of you would like to use ginac in python, or does everybody use c++/cint? Yours, Ondrej Certik

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