- GiNaC-list - ginac.de

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

11 Aug '08

On Mon, 11 Aug 2008 02:37:40 -0700 "William Stein" <wstein(a)gmail.com> wrote: > > On Mon, Aug 11, 2008 at 1:30 AM, Burcin Erocal <burcin(a)erocal.org> wrote: <snip> > > > > 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 > > This benchmark might be lame. Even the current "insanely slow" > maxima-based symbolics in Sage seem to do better than what you > just wrote above: > > sage: var('x,y') > (x, y) > sage: a = (x+y)^2 > sage: time t = sum(a^i for i in xrange(10000)) > CPU times: user 0.51 s, sys: 0.03 s, total: 0.54 s > Wall time: 0.55 s > > and > > sage: var('y,z'); 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 0.30 s, sys: 0.01 s, total: 0.31 s > Wall time: 0.32 s > > That's because the benchmark is maybe testing nothing > but memory allocation. Your benchmark doesn't call maxima at all. When you quit Sage after these lines, there is no Exiting spawned Maxima process. notice printed. > I have seen a lot of *real* benchmarks involving symbolic calculus > when sad users and students come to me and ask why their code > is 1000 times slower than Mathematica. This happened a *few* times > today at Sage Days 9 today. It also comes up in sage-support all > the time. I really need to come up with a large list of specific examples > like this, since I'm getting way too confused by benchmarks. I couldn't find any standard benchmarks, and had to come up with the one above. I think it is reflects some aspect of performance, as the power operator is very similar to a symbolic function application, and the system has to do a basic simplification like ((x+y)^2)^i = (x+y)^(2*i) for each step. Cheers, Burcin

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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

> On Mon, Aug 11, 2008 at 1:30 AM, Burcin Erocal <burcin(a)erocal.org> wrote: <snip> > > 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. On Mon, 11 Aug 2008 11:39:42 +0200 Jens Vollinga <jensv(a)nikhef.nl> wrote: > It would be quite useful for ginac if the numeric class that wraps the > cln library would allow for other libraries as well, even pure C double > precision ones. The problem in realizing this idea was always that other > libraries were missing certain features (some functions, modular > arithmetic,...) and to make up for these would incur a lot of extra > work. It didn't seem like it was worth the hassle (yet). I also think that using other libraries instead of cln in the (subclasses of) numeric class is the way to go. With William's remarks below, this becomes essential for Sage. :) On Mon, 11 Aug 2008 02:37:40 -0700 "William Stein" <wstein(a)gmail.com> wrote: > > The single big question that needs to be answered that you don't > answer in your post is the following: > > Is it likely in your opinion that with a month of hard work by you (say), > would it be possible to create something based on Ginac that would > actually satisfy the following: > > 1. Does not depend on cln. > 2. Builds in less than 8 minutes. > > I mean this as a 100% technical questions (not social, etc.). > I just had a look at the source code directory for ginac, and it is about > 20,000 lines of pretty well documented C++ code total. I have > the strong impression that the use of cln is nearly completely > encapsulated in the file numeric.cpp, which is about 2000 lines. > I'm guessing a Sage version of Ginac could simply replace numeric.cpp > by our own implementation. Of course this is possible. I am willing to put in most of the work to make this happen. However, support from the GiNaC developers for such an effort is very important. They know their code base best, with their suggestions this could be accomplished much faster. > > cln will not be included standard in Sage ever. > I could definitely see a version of ginac that doesn't depend on cln > as possible for Sage... > > -- William> Cheers, Burcin

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website down?
by Burcin Erocal 11 Aug '08

11 Aug '08

Hello, The GiNaC web site seems to be down at the moment. Does anyone know when it will be back up? Thanks. Burcin

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bug with is_polynomial?
by Jonathan Cross 09 Aug '08

09 Aug '08

Hello, I'm using GiNaC 1.4.3 built on Mac OS X. I think I've found a problem with is_polynomial when powers are involved. When there is an expression involving a non-integer power---even when the expression is independent of the dummy variable of the polynomial--- then the expression is not considered a polynomial by GiNaC. The following code illustrates the problem: (or perhaps I don't fully understand "is_polynomial"?) ------------------------- #include <iostream> #include <ginac/ginac.h> using namespace std; int main() { GiNaC::symbol x("x"); GiNaC::symbol s("s"); // here are two expressions that are both polynomials with respect to s. GiNaC::ex expr1 = sin(x) + 2*s; GiNaC::ex expr2 = pow(2,x) + 2*s; // works as expected if (expr1.is_polynomial(s)) cout << expr1 << " is a polynomial with respect to " << s << endl; else cout << expr1 << " is NOT a polynomial with respect to " << s << endl; // reports 2^x + 2s is not a polynomial in s? if (expr2.is_polynomial(s)) cout << expr2 << " is a polynomial with respect to " << s << endl; else cout << expr2 << " is NOT a polynomial with respect to " << s << endl; return 0; } ------------------------ I'm not familiar enough with the internal workings of GiNaC to make a patch, but this seems like the changes required would be fairly small. Thanks!

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Re: [GiNaC-list] cl_F_idecode.cc line 30 ?
by Chris Bouchard 30 Jul '08

30 Jul '08

I've since been able to archive an expression whose length is ~1200 lines... I'm at a loss. The only difference between the expressions that generate the error and the ones that don't seems irrelevant, but here it is. Based on the code fragment: ... ex c = TwoLoop2Pt(...); // c.nops() = 2 ex numeric = c.op(0); //returned for numerical integration ex analytic = c.op(1); //returned for analytic use, f(eps,...) ex ana_series = analytic.series(eps==0,2); ex ana_0 = ana_series.coeff(eps,0); ex ana_1 = ana_series.coeff(eps,-1); ex ana_2 = ana_series.coeff(eps,-2); ... numeric doesn't work (~1200 lines) ana_0 doesn't work (~1200 lines) ana_1 works (~1200 lines) ana_2 works (~600 lines) I guess there's either something fundamentally different between ana_0 and ana_1 (seems unlikely since they come from the same expression, c.op(1)) or there's a critical expression length right around 1200 lines. Perhaps some knowledge about cl_F_idecode.cc would help? Sincerely, Chris Bouchard ---- Original message ---- >Date: Tue, 29 Jul 2008 16:08:22 -0500 (CDT) >From: Chris Bouchard <cbouchrd(a)illinois.edu> >Subject: [GiNaC-list] cl_F_idecode.cc line 30 ? >To: GiNaC discussion list <ginac-list(a)ginac.de> > >GiNaC mailing list, > >I've run across an error with a notification request. The >error occurs while trying to archive an expression. The >error and request are: > >"Internal error: statement in file >./float/misc/cl_F_idecode.cc, line 30 has been reached!! >Please send the authors of the program a description how you >produced this error!" > >The file cl_F_idecode.cc is in the cln library and a snippet >is given here, with a comment indicating line 30: > >... >namespace cln { > >const cl_idecoded_float integer_decode_float (const cl_F& x) >{ > floatcase(x > , return integer_decode_float(x); > , return integer_decode_float(x); > , return integer_decode_float(x); > , return integer_decode_float(x); > ); // this is line 30 >} >} > >After playing around with my archive code I'm beginning to >think the error occurs when the expression being archived >becomes too long. I haven't nailed down a critical >expression length but 27 lines works while ~1200 lines >generated the error. > >I can't think of anything else that's changing. > >The expressions are individual terms from series expansions >of expressions returned from xloops function calls (eg. >TwoLoop2Pt(...)) and don't contain any noticeably offensive >pieces. > >Sincerely, >Chris Bouchard >_______________________________________________ >GiNaC-list mailing list >GiNaC-list(a)ginac.de >https://www.cebix.net/mailman/listinfo/ginac-list

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cl_F_idecode.cc line 30 ?
by Chris Bouchard 29 Jul '08

29 Jul '08

GiNaC mailing list, I've run across an error with a notification request. The error occurs while trying to archive an expression. The error and request are: "Internal error: statement in file ./float/misc/cl_F_idecode.cc, line 30 has been reached!! Please send the authors of the program a description how you produced this error!" The file cl_F_idecode.cc is in the cln library and a snippet is given here, with a comment indicating line 30: ... namespace cln { const cl_idecoded_float integer_decode_float (const cl_F& x) { floatcase(x , return integer_decode_float(x); , return integer_decode_float(x); , return integer_decode_float(x); , return integer_decode_float(x); ); // this is line 30 } } After playing around with my archive code I'm beginning to think the error occurs when the expression being archived becomes too long. I haven't nailed down a critical expression length but 27 lines works while ~1200 lines generated the error. I can't think of anything else that's changing. The expressions are individual terms from series expansions of expressions returned from xloops function calls (eg. TwoLoop2Pt(...)) and don't contain any noticeably offensive pieces. Sincerely, Chris Bouchard

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Re: [GiNaC-list] comparing symbols
by Chris Bouchard 25 Jul '08

25 Jul '08

Hi, >try the code > >cout << tree << "x = " << x << "\n"; > >then we can see what is going on. x = lst @0x8a08c70, hash=0xc, flags=0x13, nops=2 0 (symbol) @0x8a3df40, serial=62607, hash=0x771ff4, flags=0x7, domain=0 1 (symbol) @0x8a2bde8, serial=62608, hash=0x771ff4, flags=0x7, domain=0 >Maybe r_sum is called with something like > symbol f1("0"); > symbol f2("1"); > r_sum(...,lst(f1,f2),...); Wouldn't that eliminate functional dependence on the variables represented by f1 & f2, making the return value a function of "0" and "1". The end user could handle this by manually simplifying the output, but that wouldn't be optimal. Sincerely, Chris Bouchard

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Re: [GiNaC-list] comparing symbols
by Chris Bouchard 25 Jul '08

25 Jul '08

Hi, >I don't think this situation is possible (modulo compiler bugs and >things like that). > >$ cat test.cc >#include <ginac/ginac.h> >#include <iostream> >using namespace GiNaC; >using namespace std; > >int main(int argc, char** argv) >{ > lst x; > x = ex(0), ex(1); > if (is_a<symbol>(x.op(0))) { > cerr << "Huh, 0 is a symbol?" << endl; > return 1; > } > return 0; >} >$ g++ test.cc -lginac >$ ./a.out >$ echo $? >0 Hmmm... that seems to make sense. For sake of clarity I've pasted code fragment below followed by associated output. Code fragment ------------- ... namespace xloops { static ex r_sum(const ex& t, const lst& b, const lst& x, const ex& eps, int order) { // class of arguments cout << "t is class mul?: " << is_a<mul>(t) << "\n"; cout << "b is class list?: " << is_a<lst>(b)<< "\n"; cout << "b.op(0) is class add?: " << is_a<add>(b.op(0)) << "\n"; cout << "b.op(1) is class numeric?: " << is_a<numeric>(b.op(1)) << "\n"; cout << "x is class list?: " << is_a<lst>(x) << "\n"; cout << "x.op(0) is class symbol?: " << is_a<symbol>(x.op(0)) << "\n"; cout << "x.op(0) is class mul?: " << is_a<mul>(x.op(0)) << "\n"; cout << "x.op(0) is class numeric?: " << is_a<numeric>(x.op(0)) << "\n"; cout << "x.op(0) is class add?: " << is_a<add>(x.op(0)) << "\n"; cout << "x.op(1) is class symbol?: " << is_a<symbol>(x.op(1)) << "\n"; cout << "x.op(1) is class mul?: " << is_a<mul>(x.op(1)) << "\n"; cout << "x.op(1) is class numeric?: " << is_a<numeric>(x.op(1)) << "\n"; cout << "x.op(1) is class add?: " << is_a<add>(x.op(1)) << "\n"; cout << "eps is class symbol?: " << is_a<symbol>(eps) << "\n"; // value of arguments cout << "t = " << t << "\n"; cout << "b = " << b << "\n"; cout << "x = " << x << "\n"; cout << "eps = " << eps << "\n"; ... } Output ------ t is class mul?: 1 b is class list?: 1 b.op(0) is class add?: 1 b.op(1) is class numeric?: 1 x is class list?: 1 x.op(0) is class symbol?: 1 x.op(0) is class mul?: 0 x.op(0) is class numeric?: 0 x.op(0) is class add?: 0 x.op(1) is class symbol?: 1 x.op(1) is class mul?: 0 x.op(1) is class numeric?: 0 x.op(1) is class add?: 0 eps is class symbol?: 1 t = -eps b = {-1/2+eps,1} x = {0,1} eps = eps Is there any other information I could provide to shed light on this? Sincerely, Chris Bouchard

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Re: [GiNaC-list] comparing symbols
by Chris Bouchard 24 Jul '08

24 Jul '08

Hello, >Is it this what you want: > > symbol x; > ex e1 = beta(x, lst(0,1)); > ex e2 = beta(x, lst(4,1)); > > if ( e1 == beta(x, lst(0,1)) ) cout << "e1 BINGO" << endl; > if ( e2 == beta(x, lst(0,1)) ) cout << "e2 BINGO" << endl; > >Otherwise I do not completely understand your problem yet. Could you >clarify it more, then? The x-loops function I'm working with is r_sum. It's definition is (from r.cpp): static ex r_sum(const ex& t, const lst& b, const lst& x, const ex& eps, int order) and I'm trying to flag the occurrence of a certain set of argument values. The boolean operation "is_a<symbol>(x.op(i));" returns 1 for i=0,1 so I think I'm working with a list of symbols, x. Additionally, "cout << x;" yields {0,1} making me think that the symbols have been assigned numerical value. >That is what confuses me. One cannot assign numerical values to symbols >in GiNaC. One can replace symbols by numbers, of course. Perhaps I'm not correctly using/interpreting is_a<class>(ex) and/or cout<<x? Sincerely, Chris Bouchard

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comparing symbols
by Chris Bouchard 24 Jul '08

24 Jul '08

GiNaC discussion list, I'd like to discern when arguments of a pre-defined function (from another library, xloops) attain a certain value. One of the arguments is type: lst x(symbol("a"), symbol("b")); cout << x yields {0,1} and these are the values I'm looking for. I'm unable to define a relational that accurately tests the values attained by a & b. I tried: if (a==0 && ...) if (a.is_equal(0) && ...) if (a.is_zero() && ...) if (match(a,0,lst placeholder) && ...) with no success. "Probably because a is type symbol", I reasoned. So I defined lst y(symbol("c"), symbol("d")); and used in-place modification y[0] = 0; y[1] = 1; to set symbols c and d to 0 and 1, resp. I then tried the conditionals if (x==y && ...) if (x.is_equal(y) && ...) if (match(x,y,lst placeholder) && ...) with no success. How does one set up a conditional for symbols that have been assigned numeric values? Any ideas? Thanks in advance! Sincerely, Chris Bouchard

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