December 2006 - GiNaC-devel

release 1.3.6
by Jens Vollinga 14 Dec '06

14 Dec '06

Dear all, I am about to release 1.3.6 this evening (or later ... ;-) ). Please have a look at the NEWS file and the last minute submissions I did and tell me if you find something missing or wrong. @Alexei: I had to apply two of your patches manually, because the format was somehow broken. I hope I did everything correctly. @Richy: I'd like to include Chris' numerical evaluation of tgamma and friends. It's just another class added, so I think it is okay to be included because the ABI doesn't change. But because of bad experience in the past I'd like to ask you again to be sure. Regards, Jens

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Release of GiNaC 1.3.6
by Jens Vollinga 13 Dec '06

13 Dec '06

Hello everybody, GiNaC 1.3.6 is out and available. The changes are: - Better worst case behavior in heuristic gcd. - Improved collecting for sparse multivariate polynomials. - Improved collect_common_factors. - Fixed bug in numerical evaluation of multiple polylogs. - Fixed numerical integration of complex functions. - Fixed bug in tensor::replace_contr_index(). As always, this release can be downloaded from http://www.ginac.de/Download.html Best wishes, Jens

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New bug in symmetrization?
by Jens Vollinga 12 Dec '06

12 Dec '06

Hi, 'make check' gives me a failure for the paranoia exam number 17. That exam is concerned with the symmetrization of indices. Can anybody reproduce that finding? It didn't fail before I did an cvs update (my local version was rather old), so either the bug must be really new or it is one of the bugs that appear only when the ordering of expressions is disadvantageous due to the memory layout. Regards, Jens

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Numerical evaluation for tgamma, lgamma and beta.
by Chris Dams 12 Dec '06

12 Dec '06

Dear all, I added numerical evaluation for the functions tgamma, lgamma and beta to the CVS. The method employed is the Lanczos approximation as described on Wikepedia: http://en.wikipedia.org/wiki/Lanczos_approximation . (I also corrected some small errors on that page.) This method uses a fixed precision and tables are used to store coefficients. Currently the tables available are for maximally 20, 50, 100 and 200 digits. If Digits exceeds 200, no numerical evaluation is available. Best wishes, Chris

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Bugfix for numerical integration.
by Chris Dams 11 Dec '06

11 Dec '06

Dear all, I discovered that the numerical integration routine that I wrote does not handle complex functions. The inequalities in the error checking are the problem. Therefore, I added some abs-function to the code. BTW, maybe it would be a good idea to include the numerical evalution for the gamma function that I comitted last friday in 1.3 as well? Maybe it could also go into release today? Bye, Chris

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Upcoming release
by Jens Vollinga 11 Dec '06

11 Dec '06

Dear all, due to a newly discovered bug in the numerical evaluation of multiple polylogs I feel the strong urge to do a new GiNaC release very soon. Are there any unresolved issues or pending submissions that call for a delay of this release beyond the oncoming Monday? Regards, Jens

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[PATCH] gcd: fix heuristics to chose main variable properly
by Alexei Sheplyakov 03 Dec '06

03 Dec '06

Hello! Heuristic code in gcd [very] often makes bad choice of the main variable. In particular, if one of polynomials (say, p2) does not contain the variable x which _is contained_ in another one (say, p1), than gcd(p1, p2) will use such a variable as a main, so subsequent calculation becomes unnecessary complicated. Fixing this substantially improves worst case performance (less than minute versus infinity). Best regards, Alexei -- All science is either physics or stamp collecting. --- ginac/normal.cpp | 46 +++++++++++++++++++++++++++++++++++++++++++--- 1 files changed, 43 insertions(+), 3 deletions(-) diff --git a/ginac/normal.cpp b/ginac/normal.cpp index b2a4e8c..1cbf3c2 100644 --- a/ginac/normal.cpp +++ b/ginac/normal.cpp @@ -1589,11 +1589,51 @@ factored_b: } } + if (is_exactly_a<numeric>(aex)) { + numeric bcont = bex.integer_content(); + numeric g = gcd(ex_to<numeric>(aex), bcont); + if (ca) + *ca = ex_to<numeric>(aex)/g; + if (cb) + *cb = bex/g; + return g; + } + + if (is_exactly_a<numeric>(bex)) { + numeric acont = aex.integer_content(); + numeric g = gcd(ex_to<numeric>(bex), acont); + if (ca) + *ca = aex/g; + if (cb) + *cb = ex_to<numeric>(bex)/g; + return g; + } + // Gather symbol statistics sym_desc_vec sym_stats; get_symbol_stats(a, b, sym_stats); - // The symbol with least degree is our main variable + // The symbol with least degree which is contained in both polynomials + // is our main variable + sym_desc_vec::iterator vari = sym_stats.begin(); + while ( (vari != sym_stats.end()) && + (((vari->ldeg_b == 0) && (vari->deg_b == 0)) || + ((vari->ldeg_a == 0) && (vari->deg_a == 0)))) + vari++; + + // No common symbols at all, just return 1: + if (vari == sym_stats.end()) { + // N.B: keep cofactors factored + if (ca) + *ca = a; + if (cb) + *cb = b; + return _ex1; + } + // move symbols which contained only in one of the polynomials + // to the end: + rotate(sym_stats.begin(), vari, sym_stats.end()); + sym_desc_vec::const_iterator var = sym_stats.begin(); const ex &x = var->sym; @@ -1607,14 +1647,14 @@ factored_b: } // Try to eliminate variables - if (var->deg_a == 0) { + if ((var->deg_a == 0) && (var->deg_b != 0)) { ex bex_u, bex_c, bex_p; bex.unitcontprim(x, bex_u, bex_c, bex_p); ex g = gcd(aex, bex_c, ca, cb, false); if (cb) *cb *= bex_u * bex_p; return g; - } else if (var->deg_b == 0) { + } else if ((var->deg_b == 0) && (var->deg_a != 0)) { ex aex_u, aex_c, aex_p; aex.unitcontprim(x, aex_u, aex_c, aex_p); ex g = gcd(aex_c, bex, ca, cb, false); -- 1.4.3.3

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