- GiNaC-devel - ginac.de

patch for subs_algebraic
by Chris Dams 05 Mar '03

05 Mar '03

Hello, I discovered that the subs_algebraic subs_option does not yet go into subexpressions. The attached patch makes this happen. Furthermore nummatches was made into an int (it was an unsigned) because the unsigned was not used anyway and the static_cast to integer that was introduced in version 1.66.2.13 of mul.cpp completely kills subs_algebraic. I.e., it converts the maximum unsigned integer to -1, which is not good. Greetings, Chris Dams

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here we go...
by Richard B. Kreckel 01 Mar '03

01 Mar '03

This is to let folks know that Christian Bauer-san has just rolled the release of GiNaC-1.0.14 of which the only thing we know is that it works for him (tm). Can't ask him any more details. He just left the room. Hope he's fetching the champagne. Wait, I can do better and cite the NEWS file: * Improved the C-source output: complex numbers are printed correctly (using the STL complex<> template or cln::complex()), rational numbers use cl_RA() in the CLN output, and small integers are printed in a more compact format (e.g. "2.0" instead of "2.0000000e+00"). * function_options::set_return_type() and function_options::do_not_evalf_params() now actually work. Enjoy -richy. -- Richard B. Kreckel <Richard.Kreckel(a)GiNaC.DE> <http://www.ginac.de/~kreckel/>

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Yet another improvement for simplified_indexed
by Chris Dams 04 Feb '03

04 Feb '03

Hello everybody, I discovered that in the function rename_dummy_indices in indexed.cpp. The line for (unsigned i=0; i<global_size; i++) can be changed to for (unsigned i=0; i<local_size; i++) This makes the result of simplify_indexed more canonical. Reason: if I have in a sum terms in which two dummy indices occur and I also have terms in which one dummy index occurs, The terms in which one dummy index occurs always get the same one by dummy index renaming. This may make terms equal that would otherwise have been considered not to be equal. Bye, Chris Dams

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problem with simplify_indexed plus patch
by Chris Dams 04 Feb '03

04 Feb '03

Hello, I encountered the problem that after calling simplify_indexed, some of the symbols used in indices appeared three times in some of the terms. Before simplify_indexed was called this was not the case. The problem seems to be that in the function rename_dummy_indices, indices are compared by calling ex_is_equal on two of them. However, it may happen that the indices that are compared this way have the same value but different dimension. If that happens, they are considered not to be the same, but as far as dummy indices renaming is concerned but I think they should be considered the same. The attached patch is supposed to fix this. Greetings, Chris Dams

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xloops port
by Iain 01 Feb '03

01 Feb '03

Hi, What is happening with the port of xloops to GiNaC? Who, if anyone is working on it? -I __________________________________________________ Do you Yahoo!? Yahoo! Mail Plus - Powerful. Affordable. Sign up now. http://mailplus.yahoo.com

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GiNaC 1.0.13 now available
by Christian Bauer 27 Jan '03

27 Jan '03

Hello! The GiNaC Development Group (which is effectively reduced to one member now) wishes everybody a Happy New Year (belatedly) and a Happy <insert-your- favorite-religiously-motivated-around-new-year-celebration-here>, and is proud to present GiNaC 1.0.13, the latest in C++-based made-for-physicists- but-useful-for-other-people-too computer algebra library technology. Now with these exciting new features: * Contracting epsilon tensors with Euclidean indices now works. * Improved dummy index symmetrization in sums. * Added dirac_gammaL/R(), which can be used instead of dirac_gamma6/7() but are single objects, to allow for a more compact notation of Dirac strings. * Powers with negative numeric exponents are printed as fractions in the LaTeX output. * Added symbolic_matrix() for the convenient creation of matrices filled with symbols. * Added collect_common_factors() which collects common factors from the terms of sums. * simplify_indexed() converts "gamma~mu*p.mu" to "p\". As usual, it's available from our FTP server: ftp://ftpthep.physik.uni-mainz.de/pub/GiNaC Happy computing, Christian -- / Coding on PowerPC and proud of it \/ http://www.uni-mainz.de/~bauec002/

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improvement (hopefully) to subs and a patch included
by Chris Dams 27 Nov '02

27 Nov '02

Hello everybody, Here is a patch that is supposed to make substitutions, optionally, a bit more semantic (as opposed to syntactic). I also wrote a bit of documentation for it, so hava a look at the patch for a description. (Also corrected some spelling errors in the manual). This disadvantage of this patch is that it breaks compatibility of the interface. The subs method gets an extra optional argument like this ex subs(const lst & ls, const lst & lr, unsigned options = 0, bool no_pattern = false) const This is inconvenient if people have written subclasses. They will need to include this extra option everywhere. Furthermore if you use the no_pattern optional argument, you will also hava a problem. However, I think that the option-argument has the potential of being quite usefull, and the no_pattern-argument is probably only for people getting really deep into the internals of GiNaC, so I really think this is the correct order. Note that further additions to the subs-method would go into new subs_options, so that further breaking of the interface will not be necesary. However, for this reason, I guess this patch should not be included until the 1.1 release. I do not know whether diff -c -r --exclude=CVS is the most convenient format for a patch for you. If this is going to take you hours to do the patching, I will be happy to send some other format. Greetings, Chris Dams

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Error in my symmetrization patch.
by Chris Dams 21 Nov '02

21 Nov '02

Hello, Remember the symmetrization patch I sent about a week or so ago? Well it has an error and actually only works on terms of which the coefficient is not unity. On terms that have a coefficient equal to 1, it removes in a rather arbitrary way, one of the factors. Sorry for killing your library. Fortunately a patch is attached that is supposed to solve it. Greetings, Chris Dams

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problem with simplify_indexed() plus patch
by Chris Dams 11 Nov '02

11 Nov '02

Hello everybody, I have a problem with simplify_indexed(). This function tries, among other things, if some terms cancel after symmetrizing with respect to dummy indices. It then checks if the symmetrization really lessened the number of terms and if this is the case, returns the result of the symmetrization. However, this may miss opportunities for simplification. Imagine that we have a sum of four terms, say, T = t1 + t2 + t3 + t4, and that after symmetrization t1 and t2 cancel. However, it turns out that symmetrization yields six terms. We have T_symm = t3,1 + ... + t3,6 + t4,1 + ... + t4,6. This contains twelve terms, which is more than the original four ones, and therefore, is not accepted as a simplification. However, as a (more or less) intelligent human being I do not find it very difficult to use the just presented information to think of a simpler expression for T. Furthermore, even if, in such a case, symmetrization yields a smaller number of terms, the result may be somewhat awkward. What if I have objects carrying a three-dimensional index for which I use symbols a, b, c, etcetera and a four-dimensional index for which I use symbols mu, nu, sig, etcetera. The symmetrized result may have latin letters in places where I would normally expect greek ones and vice versa. Both problems sketched above are solved if one uses the symmetrized terms for determining what cancels but the original terms to get the, hopefully, simplified result. A patch is attached that is supposed to make this happen. Greetings, Chris Dams

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GiNaC 1.0.12 "Halloween Edition" now available
by Christian Bauer 30 Oct '02

30 Oct '02

Hello! Tired of cutting faces into pumpkins, preparing poisoned cookies for your neighbours' kids, and weeding out the spam from our mailing lists? :-) Why not try GiNaC 1.0.12 which comes with these exciting features: * Fixed a bug in power::expand() that could produce invalid expressions. * The input parser no longer ignores extra data following accepted input. * Improved the CLN C-source output (integers are printed as integers, and floating point numbers include the precision). * Fixed a problem in the LaTeX-output of negative fractions. * Added print_latex() and print_csrc() to ginsh. * The sprem() function is now public. Available now from your favorite FTP server: ftp://ftpthep.physik.uni-mainz.de/pub/GiNaC Have fun, Christian -- / Coding on PowerPC and proud of it \/ http://www.uni-mainz.de/~bauec002/

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