- GiNaC-devel - ginac.de

Newest version of my patches
by Chris Dams 05 Oct '05

05 Oct '05

Dear all, I discovered that in my patch there was is_a<whatever> that should have been an is_exactly_a<whatever>, so here's a new patch. Besides that, it contains all changes that I sent recently. Best wishes, Chris

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Substituting and dummy indices.
by Chris Dams 04 Oct '05

04 Oct '05

Dear GiNaCers, Substitution and dummy index renaming also seem to have some problems getting along with each others. Here's a patch that seems to solve it and also includes the changes I mailed last evening ("Another patch"). Best wishes, Chris

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Another patch
by Chris Dams 03 Oct '05

03 Oct '05

Dear all, The idea of renaming dummy indices when expressions are raised to a power or when this is necessary in the case of a subsitution, is a great idea. However, it seems rather inconsistently implemented. E.g., if you calculate x^2 as power(x,2) then dummy indices are renamed but not if you do it like x*x. The attached patch makes renaming work if multiplications are constructed using operator* or by the mul::mul (exvector) constructor. Furthermore, the function rename_dummy_indices_uniquely was not aware of the existence of spinidx. The patch also corrects this. Best wishes, Chris

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Speeding up simplify_indexed(): 2nd try
by Chris Dams 03 Oct '05

03 Oct '05

Dear all, Here is a new attempt at the patch. The problem with the previous one was that if one symmetrizes only amongst indices of precisely the same type, also renaming of indices should be done taking these types into account. Another advantage of this is that if a user uses for instance mu and nu for indices with a variance, these will no longer end up being used as indices without variance. I think this makes output more readable. Best, Chris

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patch for simplify_indexed.
by Chris Dams 01 Oct '05

01 Oct '05

Dear developers, When simplify_indexed() is called two symmetrizations w.r.t dummy indices are performed. In these two cases symmetrization w.r.t. all dummy indices is done. However, it is also possible to do symmetrization with respect to ordinary idx-es, varidx-es and spinidx-es seperately. The latter is potentially much faster. E.g. Today I had an example where some terms contained 5 ordinary dummy indices and 2 dummy indices with variance. In this case a factor of 21 fewer terms are generated by the latter option. (I.e. 7!/5!/2!=21). Therefore symmetrizing seperately can be much faster. A patch is attached. Best wishes, Chris

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Function & Power patch
by Vladimir Kisil 26 Sep '05

26 Sep '05

Dear All, There are many functions (abs, Heaviside, exp) which possess some power-simplification rules. I propose a patch to power.cpp and function.pl which allows to defines such rules in a way similar to derivative rules of functions. With the help of this I slightly improve the definition of abs() and it work now in this way: #include <ginac/ginac.h> using namespace GiNaC; int main(){ realsymbol a("a"); cout << pow(abs(a), 2) << endl; // -> a^2 cout << pow(abs(a), 3) << endl; // -> abs(a)^3 symbol r("r"); cout << pow(abs(r), 2) << endl; // -> abs(r)^2 cout << pow(abs(r), 3) << endl; // -> abs(r)^3 } i.e. pow(abs(a), 2*n) is simplified to pow(a, 2*n) for real a. I also delete a duplicated line from ginac.texi. If it will be useful to add a definition of Heaviside function to the GiNaC core, I can send a patch as well. Best wishes, Vladimir -- Vladimir V. Kisil email: kisilv(a)maths.leeds.ac.uk -- www: http://maths.leeds.ac.uk/~kisilv/

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Patch for adaptivesimpson.
by Chris Dams 15 Sep '05

15 Sep '05

Dear developers, Could you apply the attached patch to integral.cpp? It adds some checks to adaptivesimpson to see whether the boundaries of integration and the integration error really are numbers and, as discussed with Richy, it makes the lookup table take into account that adaptivesimpson may be called with the same integral but different precision. Best wishes, Chris

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Numerical integration in GiNaC
by Richard B. Kreckel 13 Sep '05

13 Sep '05

Hi Chris! I was playing with the adaptive Simpson function and found some problems evaluating numerically a (well-behaved) integral. I've a couple of questions: 1) Why the decision to *not* couple the precision to the value of Digits? Coupling it to Digits would make it available in Ginsh. Wouldn't it do the right thing in almost all cases? 2) Are variations of Simpson's rule really attractive for numerical evaluation? Have you considered/tried something funkier (maybe Romberg's method) or is that a particularly smart implementation? 3) Probably an oversight: the last argument to the adaptivesimpson function is unused. Instead, the code always uses the default. Best wishes -richy. -- Richard B. Kreckel <http://www.ginac.de/~kreckel/>

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patch for power::expand_mul
by Chris Dams 09 Sep '05

09 Sep '05

Dear developers, Could you change the line if (get_all_dummy_indices(m).size() > 0) { that occurs in the function power::expand_mul in power.cpp into if (get_all_dummy_indices(m).size() > 0 && n.is_positive()) { Reason: I sometimes use algebraic substitution for expressions involving indices. For instance using the pattern indexed(UL1inv,wildgen,wildgen2)*indexed(UL1,wildgen2,wildgen3) ==delta_tensor(wildgen,wildgen3) to cancel a matrix multiplied with its inverse. Internally, algebraic subsitution divides by the factors it wants to get rid of but since Vladimir Kisils patch this goes wrong if these factors contain a contraction. Best wishes, Chris

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TINFO policy (WAS: [GiNaC-devel] Another clifford patch)
by Vladimir V. Kisil 27 Jul '05

27 Jul '05

>>>>> "RK" == Richard B Kreckel <kreckel(a)ginac.de> writes: RK> This sounds like a helluvagood idea. The only thing I'm worried RK> about is I am also thinking about some kind of policy to choose a right TINFO for new homemade GiNaC classes. It will be good to avoid possible clashes in the case of all such examples collected in one place. Best, -- Vladimir V. Kisil email: kisilv(a)maths.leeds.ac.uk -- www: http://maths.leeds.ac.uk/~kisilv/

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