January 2014 - GiNaC-devel

RFC: step function and Pauli matrices
by Matthias Dellweg 05 Feb '14

05 Feb '14

Dear all, please consider the attached patches: GiNaC is able to check whether expressions are sums of possymbols. We can use that to evaluate some step functions immediately: 0001-Evaluate-step-whenever-possible.patch This should be a generic transformation from an integral with a step function to step functions times integrals without: 0002-Integrate-when-integrand-is-a-product-with-a-step-fu.patch This patch implements Pauli matrices in the same manner as in color.cpp (shamelessly borrowed...): 0003-Implementation-of-Pauli-matrices.patch As opposed to the color algebra, a product of pauli objects can always be reduced to a linear combination of single pauli objects: 0004-New-function-pauli_normalize.patch Best wishes, Matthias Dellweg

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Ulrich, please add me to your LinkedIn network
by Jose Antonio Garcia Peiro via LinkedIn 29 Jan '14

29 Jan '14

LinkedIn ------------ Jose Antonio Garcia Peiro requested to add you as a connection on LinkedIn: ------------------------------------------ I'd like to add you to my professional network on LinkedIn. Accept invitation from Jose Antonio Garcia Peiro http://www.linkedin.com/e/-smpzss-hr0w89pg-4c/pQQaivesQERn6ZpSpQQtivesQEgGd… View profile of Jose Antonio Garcia Peiro http://www.linkedin.com/e/-smpzss-hr0w89pg-4c/rso/68581204/4MAI/name/172008… ------------------------------------------ You are receiving Invitation emails. This email was intended for Ulrich Loup. Learn why this is included: http://www.linkedin.com/e/-smpzss-hr0w89pg-4c/plh/http%3A%2F%2Fhelp%2Elinke… (c) 2012, LinkedIn Corporation. 2029 Stierlin Ct, Mountain View, CA 94043, USA.

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[SCM] GiNaC -- a C++ library for symbolic computations branch, master, updated. release_1-4-0-412-g5acfced
by git＠ginac.de 28 Jan '14

28 Jan '14

This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GiNaC -- a C++ library for symbolic computations". The branch, master has been updated via 5acfced77964d811d66f83e83b8fa06d77f3edd0 (commit) from ff604e21b9108236522fb59ba5f72ba1b88b374e (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- commit 5acfced77964d811d66f83e83b8fa06d77f3edd0 Author: Stefan Weinzierl <stefanw(a)thep.physik.uni-mainz.de> Date: Tue Jan 28 08:58:06 2014 +0200 Li_eval(): avoid the "numeric::operator>(): complex inequality" exception. Basically the problem is that 1 + 0.0*I is equal to 1, but checking if the former is positive results in the the "numeric::operator>(): complex inequality" exception. This behavior is definitely inconsistent and should be fixed. As a work around teach Li_eval and convert_parameter_Li_to_H to explicitly convert 1 + 0.0*I to 1 (and -1 + 0.0*I to -1, respectively). [Alexei Sheplyakov: comment the code a little bit, otherwise it looks weird] ----------------------------------------------------------------------- Summary of changes: ginac/inifcns_nstdsums.cpp | 19 +++++++++++++++++-- 1 files changed, 17 insertions(+), 2 deletions(-) hooks/post-receive -- GiNaC -- a C++ library for symbolic computations

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Floating complex numbers
by Stefan Weinzierl 21 Jan '14

21 Jan '14

Hi, I'm currently fixing some bugs in inifcns_nstdsums.cpp and came across the following strange behaviour: The GiNaC manual says "Complex numbers are automatically converted to real numbers if the imaginary part becomes zero". However, this does not seem to be the case, as the following lines show: ex w1 = numeric(3)+I*numeric(2); ex w2 = numeric(2)+I*numeric(2); ex w3 = w1-w2; if ( (w3 == 1) && ex_to<numeric>(w3).is_real() ) std::cout << "o.k., equal to one and real" << std::endl; ex z1 = numeric(3)+I*numeric("2.1"); ex z2 = numeric(2)+I*numeric("2.1"); ex z3 = z1-z2; if ( (z3 == 1) && !ex_to<numeric>(z3).is_real() ) std::cout << "bug, equal to one, but not real" << std::endl; The bug seems to be in CLN, as it does not downgrade z3 to an instance of cln::cl_R_ring. Currently this leads to an error in the file inifcns_nstdsums.cpp. In this file a variable z is first checked to be equal to +1 or -1, and later on a comparison z>0 is carried out. The comparison leads to the exception numeric::operator>(): complex inequality, since for the computer z is equal to +/- 1, but not real, similar to the last line in the code fragment above. I can work around this bug in the file inifcns_nstdsums.cpp, but the clean solution would be to fix this in CLN. Any chances for that ? Best wishes, Stefan

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[SCM] GiNaC -- a C++ library for symbolic computations branch, master, updated. release_1-4-0-411-gff604e2
by git＠ginac.de 12 Jan '14

12 Jan '14

This is an automated email from the git hooks/post-receive script. It was generated because a ref change was pushed to the repository containing the project "GiNaC -- a C++ library for symbolic computations". The branch, master has been updated via ff604e21b9108236522fb59ba5f72ba1b88b374e (commit) via 22dbae3e0d20ffd06e405100c295aeabfc0dfa5a (commit) via 9a69e9de24bc228830b5cdf02648edd860e04f8e (commit) via a4ad8cb5a89db1405fbdcaae12aef3c07904efd8 (commit) from 98433210d31a34b55c8283eb7fb7767d6c830e14 (commit) Those revisions listed above that are new to this repository have not appeared on any other notification email; so we list those revisions in full, below. - Log ----------------------------------------------------------------- commit ff604e21b9108236522fb59ba5f72ba1b88b374e Author: Stefan Weinzierl <stefanw(a)thep.physik.uni-mainz.de> Date: Sun Jan 12 22:31:22 2014 +0000 Fix S_num for arguments close to the sixth root of unity or its conjugate. The method S_num within the Nielsen polylogs used to map the region abs(x)<=1 && abs(x)>0.95 && abs(1-x)<=1 && abs(1-x)>0.95 infinitely many times onto itself. This infinite recursion is now avoided. This however reveals the next problem: The numerical convergence in this region is very slow. Within the Nielsen polylogs there is no transformation available to improve the convergence. However we can use the (1-x)/(1+x) transformation within the harmonic polylogs. In order to avoid another infinite recursion I have inserted a few hold()'s in the method H_evalf, otherwise we would fall back immediately again to Nielsen polylogs. The hold()s should have been there anyway. commit 22dbae3e0d20ffd06e405100c295aeabfc0dfa5a Author: Stefan Weinzierl <stefanw(a)thep.physik.uni-mainz.de> Date: Sun Jan 12 22:19:56 2014 +0000 Fix G3_evalf and G3_eval for real and negative x. The user supplied signs of the imaginary parts are only relevant for x real and positive. A negative sign in the case of x real and negative is irrelevant (there is no branch cut) and led to wrong results. This is now avoided. commit 9a69e9de24bc228830b5cdf02648edd860e04f8e Author: Stefan Weinzierl <stefanw(a)thep.physik.uni-mainz.de> Date: Sun Jan 12 22:07:28 2014 +0000 Within mLi_numeric, set signs of the imaginary parts correctly for G_numeric. commit a4ad8cb5a89db1405fbdcaae12aef3c07904efd8 Author: Stefan Weinzierl <stefanw(a)thep.physik.uni-mainz.de> Date: Sun Jan 12 21:58:12 2014 +0000 Avoid calling log(1-x) for x=1 in Li_projection. ----------------------------------------------------------------------- Summary of changes: ginac/inifcns_nstdsums.cpp | 62 ++++++++++++++++++++++++++++++++----------- 1 files changed, 46 insertions(+), 16 deletions(-) hooks/post-receive -- GiNaC -- a C++ library for symbolic computations

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Symbolic integration of trigonometric functions
by Jan 12 Jan '14

12 Jan '14

Hi, the Ginac documentation says: "GiNaC is not very good (yet?) at symbolically evaluating integrals" so I though I might help it along. Code for sin() and cos() is in this branch which is based on the current master: https://github.com/jrheinlaender/ginac/tree/jrheinlaender/integral and if you like it I might add more functions. Jan Rheinländer

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