- GiNaC-list - ginac.de

extending the symbol
by Krishna Mohan Gundu 27 Oct '08

27 Oct '08

Hi, I am adding a light weight support for vector algebra in ginac. I am aware that it can be done through Clifford algebra, but the output is almost incomprehensible to debug. My problem is this. When a request like inner_product(lhs, rhs) is made, where one of lhs and rhs is not a vector, I would like to replace the inner_product with a regular product. How can I achieve this? I am planning to do it as follows 1) extend a symbol to a vector 2) determine if both lhs and rhs have a hanging vector by traversing the expressions in lhs and rhs and by testing for is_a<vector> Is there a better way to test if a symbol is a vector? If not what is the simplest way to extend symbol? thanks, Krishna.

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a few simple useful features
by Krishna Mohan Gundu 26 Oct '08

26 Oct '08

Hello All, 1) I find something like GINAC_DECLARE_REGISTERED_CLASS_INLINE to be very useful to define virtual member functions like archive, unarchive etc. inside the class definition. (This macro should not declare these functions, ofcourse) 2) Should numeric and ex have constructors that take std::complex<double> to initialize a complex number? This makes integration of GiNaC into other libraries simpler. cheers, Krishna.

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GiNaC Licensing
by Graham Hemingway 22 Oct '08

22 Oct '08

Hello, I am working on an open source 3D solid modeling kernel ( http://wildcat-cad.blogger.com and http://wildcat-cad.googlecode.com) It allows users to sketch 2D profiles and extrude them into 3D to form mechanical parts. The 2D sketches are constrained with dimensions (lengths, angles, etc.) and these constraints naturally form a system of equations. An unrelated project (http://code.google.com/p/psketcher) has developed a very nice solver for these systems of equations. The psketcher project uses GiNaC as its mathematical engine. I would like to incorporate the psketcher solver into my kernel, but there may be a conflict in licenses. My project is released under the BSD license, while I understand GiNaC to be under the GPL. Is there any way to reconcile this problem other than changing to a different license? I would love to use GiNaC for a couple of other purposes within my project also. Any help would be appreciated. Cheers, Graham

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spcializing print function
by nomad 04 Oct '08

04 Oct '08

Hello, I am trying to define a new algebraic class the easy way. The documentation is a bit confusing in this regard. It mentions typedef structure<sprod_s> sprod; and then proceeds with void sprod::print(const print_context & c, unsigned level) const { ... } How is this possible as structure<> already defines print() member function? Can someone give more specific details? thanks, Krishna. -- View this message in context: http://www.nabble.com/spcializing-print-function-tp19809899p19809899.html Sent from the Ginac - General mailing list archive at Nabble.com.

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multiplying a matrix with 0 makes it become a scalar 0
by dummy-address＠web.de 21 Sep '08

21 Sep '08

Hi! symbol a("a"), b("b"), c("c"); matrix blah(3,1); blah = a,b,c; cout << "blah: " << blah << endl; //output: // blah: [[a],[b],[c]] cout << "3*blah: " << 3*blah << endl; //output: // 3*blah: 3*[[a],[b],[c]] cout << "(3*blah).evalm(): " << (3*blah).evalm() << endl; // output: // [[3*a], [3*b], [3*c]] cout << "0*blah: " << 0*blah << endl; // output: // 0 cout << "(0*blah).evalm(): " << (0*blah).evalm() << endl; // output: // 0 I don't like this behaviour. Is it supposed to be that way or is this a bug? Is there a nice way to prevent a matrix from losing its row and column information? Regards Al Capone

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solving differential equatrions symbolically or numerically with C++
by Alessandro Bernardini 01 Sep '08

01 Sep '08

Hello, I am looking for a C++ library for doing symbolic or numeric computations within C++ programs. I would like a class that provides usefull tools for scientific computing (symbolic and numeric computations). I woluld like tools like in Mathematica (or Maple), but in a C++ class library !! Of particular importance is the solution of differential equations (symbolically or numerically; for ODEs or PDEs), so as variable precision arithmetic. Of course symbolic sympflification is very important. Is GiNaC the right tool for me, for doing symbolic computing and solving differential equations ? Or SymbolicC++ ? Can this libraries be an alternative to the functionality of mathematica (when used in C++ programs of course ... ) ? Thank you very very much for a short answer ... Alex.

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FYI: CLN fork
by Alexei Sheplyakov 27 Aug '08

27 Aug '08

Hello! CLN is a great library, but it has a number of problems. 1. CLN can be built only with GNU C++ compiler. Even worse -- some bits of CLN (in particular, include/cln/modules.h) work only with specific versions of GCC, so CLN can break at any moment (this actually happens with every new [major] release of GCC). 2. The code is a bit obfuscated. 3. The build scripts are extremely user- and hacker-hostile. Since CLN developers keep [silently] refusing patches addressing these issues, I've decided to fork CLN. The code can be obtained from git repository: git://ffmssmsc.jinr.ru:443/varg/cln.git To view the repository on-line point your browser to http://ffmssmsc.jinr.ru/~varg/git/gitweb.cgi?p=varg/cln.git Best regards, Alexei -- All science is either physics or stamp collecting.

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GiNaC as the symbolic manipulation engine in Sage
by Burcin Erocal 21 Aug '08

21 Aug '08

Hello, This e-mail is going to two lists (sage-devel and ginac-list), so there will be some redundant information. I hope you still take the time to read it to the end, where you can see some cool benchmarks. :) William often states that Sage is now capable of fully supporting his research. Unfortunately, for my research in symbolic summation & integration Sage lacks some of the very basic facilities. If Sage is to become a "viable alternative to Maple and Mathematica", it needs to be able to support research in symbolic computation, and development of new algorithms. At a bare minimum this means providing support for fast symbolic manipulation and arithmetic as well as some form of pattern matching. Most people reading this e-mail are probably aware of the shortcomings of the symbolics code in Sage at the moment, but here are some timings to make the situation clear. MMA: In[1]:= a = (x+y)^2; In[2]:= Timing[Sum[a^i,{i,1,10000}];] Out[2]= {0.028001, Null} Maple: > a:=(x+y)^2: > st:=time(): t:=add(a^i,i=1..10000): time()-st; 0.024 Sage via the maxima interface didn't finish this task in < 5 minutes. Timings for some of the alternatives that were considered as a backend for symbolics: Sympy (version 0.6.0 in Sage-3.0.6) didn't complete the above operation in < 5 minutes. sympycore (SVN revision 1047): sage: from sympycore import Symbol sage: x, y = Symbol("x"), Symbol("y") sage: a = (x+y)^2 sage: %time t = sum( [a^i for i in xrange(10000)] ) CPU times: user 3.45 s, sys: 0.78 s, total: 4.23 s Wall time: 4.23 s Note that even with its highly optimized structures, sympycore is far from reaching Maple/MMA performance from pure Python. At the ACA'08 conference, I've met some physicists using GiNaC (http://www.ginac.de/) a C++ library that provides symbolic manipulation and pattern matching facilities. Its lastest release was on Apr 04 2008, it also has extensive documentation, and active mailing lists. I wrote a basic Cython wrapper to benchmark its performance. Here are the numbers: sage: var("x y z",ns=1) (x, y, z) sage: a = (x+y)^2 sage: %time t = sum( [a^i for i in xrange(10000)] ) CPU times: user 1.83 s, sys: 0.00 s, total: 1.83 s Wall time: 1.83 s And some more: sage: b = (y+z)^2 sage: %time t = sum( [a^i*b^j for i in xrange(1,200,5) for j in xrange (1, 300, 3)] ) CPU times: user 0.35 s, sys: 0.00 s, total: 0.35 s Wall time: 0.36 s Maple: > a := (x+y)^2: > b := (y+z)^2: > st := time(): S := 0: for i from 1 to \ > 200 by 5 do for j from 1 to 300 by 3 d\ > o S := S+a^i*b^j end do end do: time() - st; 3.464 MMA: In[1]:= a=(x+y)^2; In[2]:= b=(y+z)^2; In[3]:= S = 0; In[4]:= Timing[ Do[ Do[ S=S+a^i*b^j, {j, 1, 300, 3}], {i, 1, 200, 5}]; ] Out[4]= {11.0527, Null} Thinking that these timings might be off because I don't know the proper way to do this in Maple or MMA, here is a different python timing: sage: s = a.parent(0) sage: st = cputime() sage: for i in xrange(1,200,5): ....: for j in xrange(1,300,3): ....: s += a^i*b^j ....: sage: et = cputime() sage: et-st 0.42002600000000001 Like many other subsystems in Sage, the symbolic arithmetic / manipulation backend should consist of a c/c++ library with a wrapper which allows the user to implement more advanced algorithms such as substitutions/tree traversals in Sage/Cython. One can of course implement the arithmetic in pure C from Cython, but this goes very much against the Sage philosophy of not reinventing the wheel. I suggest GiNaC should be the library we use in Sage for this backend. Its performance is very impressive and it can get us to a competitive position in the short term. Once we have a stable symbolics interface, we can work on more advanced algorithms such as limits / integration and improving the backend at the same time. For those who want to try my wrapper, you need to install these two spkgs (in order): http://sage.math.washington.edu/home/burcin/spkg/cln-1.2.2.spkg http://sage.math.washington.edu/home/burcin/spkg/ginac-1.4.3.spkg And apply this patch: http://www.risc.jku.at/people/berocal/sage/ginac-wrapper.patch While GiNaC seems to be the best option for Sage, it has some problems (apart from the awkward capitalization of the name which is a pain to type). - It takes ages to build The packages above took ~25 minutes to build on my desktop machine (15 for cln, 9 for ginac) - cln seems to support on only gcc, which might be a problem for the windows port (which will be using ms compilers) - cln duplicates functionality which is provided by different libraries already distributed with Sage (mpfr, mpir, flint) at a considerable speed penalty. - Creating symbolic functions at runtime is not supported. I can probably work around this in the wrapper. I've done something similar in my SCrypt package which provides symbolic computation capabilities over characteristic 2 for experimenting in crypto. It relies on PolyBoRi for arithmetic, which is just a polynomial library, i.e. knows nothing about symbolics. It would still be better to have support for runtime creation of symbolic functions in GiNaC. - IIRC, GiNaC documentation suggests the printing order for the variables is stable between different sessions, regardless of creation order. However, running the doctests in the experimental wrapper reveals different results. We may need to write a custom pretty printer. - The gethash() function of GiNaC objects doesn't return stable results, which is probably the cause of the problem above. We need a stablehash() function. I think all these problems can be resolved with some effort, and even the speed of basic arithmetic in GiNaC can be improved with modifying it's data structures. Admittedly some of these tasks are much easier than others, but supporting an already stable and mature library like GiNaC is a much better approach than trying to write our own. Thoughts? Comments? Cheers, Burcin

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Fw: [sage-devel] Re: GiNaC as the symbolic manipulation engine in Sage
by Burcin Erocal 11 Aug '08

11 Aug '08

Can I get some help with these questions? I don't see a link to a bug tracker on the web site. Is there a list of known bugs? I guess the test code is placed under the directory check/ in the source tree? Thanks. Burcin Begin forwarded message: Date: Mon, 11 Aug 2008 08:24:52 -0700 From: "William Stein" <wstein(a)gmail.com> To: sage-devel(a)googlegroups.com Subject: [sage-devel] Re: GiNaC as the symbolic manipulation engine in Sage Burcin, 1. does Ginac (or the part we plan to use) have *any* known bugs at all? 2. does Ginac have a test suite? 3. does ginac have a bug tracker? 4. what does Valgrind say about the quality of the code when run on the test suite? memory leaks? -- William

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Re: [GiNaC-list] [sage-devel] Re: GiNaC as the symbolic manipulation engine in Sage
by Burcin Erocal 11 Aug '08

11 Aug '08

Hi, I forwarded your questions to the ginac list. I'll try to answer as much as I know. On Mon, 11 Aug 2008 08:24:52 -0700 "William Stein" <wstein(a)gmail.com> wrote: <snip> > Burcin, > > 1. does Ginac (or the part we plan to use) have *any* known bugs at all? I can't find a public bug tracker on the web site. They suggest sending bugs to the mailing list. > 2. does Ginac have a test suite? Some of the files under the check/ directory seems to verify correctness. > 3. does ginac have a bug tracker? > 4. what does Valgrind say about the quality of the code when run on > the test suite? memory leaks? I haven't run it through valgrind at all. Maybe mabshoff can lend a helping hand here? Burcin

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