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Problems with linking GiNaC
by paul81＠webb.de 24 Sep '03

24 Sep '03

Hello, I'm new to GiNaC. In fact I've just installed the Debian package. But when I tried to compile the examples given in the section "A Tour of GiNaC" in the info pages it won't work. The object file is correctly made; but the linking process just returns a lot of errors. I used the command g++ $(ginac-config --libs) example.c++ ld returns many error messages (too much to send them). Basicly there two types. First many messages like example.o(.text+0x47): In function `main': : undefined reference to `GiNaC::symbol::symbol[in-charge](std::basic_string<char, std::char_traits<char>, std::allocator< char> > const&)' And for (I think) every reference in the object file. And second there also messages like: /usr/lib/libginac.so: undefined reference to `cerr' /usr/lib/libginac.so: undefined reference to `cln::compare(cln::cl_R const &, cln::cl_R const &)' (Very much of them, too). I have checked ginac-config. It seems to report the right libraries. When I tried static linking some of the messages disappeared, but only a few. Can anyone tell me, how I can get those examples run? Thank in advance, Paul PS: My systems configuration: g++ (GCC) 3.2.3 20030309 (Debian prerelease) GiNaC 1.0.11-1 (the debian packages: libginac-dev 1.0.11-1 & libginac0 1.0.11-1) CLN 1.1.5-1 (Debian: libcln2 1.1.5-1) and Debian GNU/Linux 2.4.17

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Subscribe
by hadi＠kmkl.ocean.itb.ac.id 27 Aug '03

27 Aug '03

Helo Moderator, I want to join this club,so bring me in to the millist! Thanks!

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symbol non-commutative?
by Kent-Andre Mardal 25 Aug '03

25 Aug '03

Hi, I wonder if it is possible to make symbols non-commutable. The reason is that I want to invert systems of matrices, [[A B], [C D]] where A, B, C and D are matrices. The matrices are invertible, but I do not want to say anything about their structure. I have made a subclass mystring of basic as described in sec. 6.3. and redefined return_type: unsigned return_type(void) const { return return_types::noncommutative; } and it works fine: (a+b)*(a+b) = a*a+a*b+b*a+b*b However, when I make a matrix of and try to solve it, the program abort. I have also tried to make a subclass of symbol, but this class does not seem to be as easy to subclass as basic. Any hints ? Kent-Andre Mardal

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GiNaC 1.1.3 released
by Christian Bauer 22 Aug '03

22 Aug '03

Hello! Desparate for an excuse to open a bottle of wine (because Booze really satisfies: Booze takes a dull coding session and makes it better. A day without Booze is like a day without sunshine. This GiNaC release is brought to you by the National Booze Council. Remember: Booze makes you popular and heals all wounds.) we decided to release GiNaC 1.1.3, featuring: - New symbolic functions for better integration with nestedsums: (multiple) polylogarithm Li(), Nielsen's generalized polylogarithm S(), harmonic polylogarithm H(), and multiple zeta value mZeta(). - A new exhashmap<T> template intended as a drop-in replacement for std::map<ex, T, ex_is_less> using GiNaC's hashing algorithms. It should come as no surprise to you that you can download it from ftp://ftpthep.physik.uni-mainz.de/pub/GiNaC/ Have a nice weekend, Christian -- / Physics is an algorithm \/ http://www.uni-mainz.de/~bauec002/

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GiNaC 1.1.2 now available
by Christian Bauer 11 Aug '03

11 Aug '03

Hello! We haven't had an update in a while, and the radical new features of GiNaC 1.2 are taking a bit longer, so I've packed up the latest fixes of the 1.1 line in a nice release: GiNaC 1.1.2 - Fixed a bug in the unarchiving of sums and products: terms were not reordered in a canonical way. - Fixed a bug in normal()/numer_denom(): denominator was not made unit normal if it was a simple number. - Improved the speed of subs() in some cases. As usual, it's on ftp://ftpthep.physik.uni-mainz.de/pub/GiNaC For oldskool fans, there's also a GiNaC 1.0.15 that contains the same two bug fixes. Bye, Christian (who has nearly completed liquefaction; what's the boiling point of human tissue?) -- / Physics is an algorithm \/ http://www.uni-mainz.de/~bauec002/

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Re: C++ code generation: any way of deflating large expressions?
by hugo_lec＠club-internet.fr 21 Jul '03

21 Jul '03

Hello, I also worked on such a program : I have to convert huge expressions in optimized C++ code (to automate design of finite element code). I tried to make something which does not calculate two times the same thing. There's an algorithm to use the less temporary variables as possible (in order to help the compiler to optimize). It also looks for factorizations with * and + (A=x*y; B=sin(x*y*z) -> B=sin(A*z)... ) and for the cost of operations (A=x/y; B=z/y; gives double tmp0=1/y; A=x*tmp0; B=z*tmp0)... It can generate code for huge expressions in a few seconds. It is a bit crappy because it does not use the internal representation given by GiNaC. But if someone wants to clean it... For now it is usable enough for me. A simple example : Optimized_ex_output mm("float"); symbol x ("x"), y ("y"), z ("z"), u("u"), v("v"); mm.add ("A{1]", x/u*v, true); mm.add ("B", (x+y)/u*v+cos((x+y+z)*y), false); mm.write(std::cout,2); // 2 spaces before each line mm.display_tree(); // graph output produces : float reg0 = v; float reg1 = z; float reg2 = u; float reg3 = x; float reg4 = y; float reg5 = reg3; reg3 += reg4; reg2 = 1 / reg2; float reg6 = reg2; reg2 *= reg3; reg2 *= reg0; reg0 *= reg6; reg3 += reg1; reg4 *= reg3; reg0 *= reg5; A{1] += reg0; reg4 = cos( reg4 ); reg4 += reg2; float B = reg4; (and a nice dot graph) In the near future, I've planed to allow generation of vectorial code to produce 4x the same calculi on different data. I've also planed to generate code for GPUs but not for the near future. Hugo LECLERC.

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Changing symbol string names on-the-fly
by Dr. Vassilis S. Vassiliadis 11 Jul '03

11 Jul '03

Is it possible to change on-the-fly the string names used in a symbol? For example, I am considering programs with several thousands of variables and wish to output the code for the expressions in csrc-format. The names used internally utilize the object-partitioning of my code e.g. : symbol x("system[1].composition.x[2]") The output in raw C++ form is desired to be a simple counting scheme e.g. for the above symbol: "var[101]" will be substituted. I have tried to use an auxiliary vector list with new symbols and then substitute the new symbols for the old, using .subs(). However, when the number of substitutions is beyond say a couple of hundred even a 2.5 GHz machine cannot run the problem efficiently. I proceeded to test further abstract examples of substitutions and found that the .subs() method can indeed be extremely slow (inefficient?) in general. Without resorting to brute force outputing and replacing of strings, I wonder if there is an elegant and economical way to do the above in GiNaC. Vassilis. ----------------------------------------------------------------- Dr. Vassilis S. Vassiliadis, Lecturer, UNIVERSITY OF CAMBRIDGE, DEPARTMENT OF CHEMICAL ENGINEERING Pembroke Street, Cambridge CB2 3RA, UK. Tel: (reception): +44 1223 334777 Fax: (departmental): +44 1223 334796 WWW: www.cheng.cam.ac.uk/~vsv20 e-mail: vsv20(a)cheng.cam.ac.uk -----------------------------------------------------------------

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how to subs t.i with i*t.i
by Yong Xiao 11 Jul '03

11 Jul '03

Hi, it seems that the following lines ex e1 = indexed(t,i); e1.subs(indexed(t,idx(i_,3))==idx(i_,3).get_value()*indexed(t,idx(i_,3))); ,where i and i_ are idx and wildcard objects respectively, doesn't substitute t.i with i*t.i. t.i still remains it's original form. Is there any way I can do such subs: t.i-->i*t.i? Thank you. Yong

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The speed of subs()
by Christian Bauer 10 Jul '03

10 Jul '03

Hi! Prompted by the recent discussion I've done some timings and experiments with subs(). Two benchmarks were used: a) "Binary tree" constructs a binary expression tree (alternating sums and products) of depth N with symbols as the leaves (e.g. N=3 leads to (a1+a2)*(a3+a4)+(a5+a6)*(a7+a8)), then substitutes all 2^N symbols by a set of new symbols (using one subs() call). b) "Linear polynomial" constructs an expression of the form "1+a1+a1*a2+ a1*a2*a3+...+a1*...*aN" of length N and also substitutes all N symbols by new ones. The time measured was only the time for the subs() step, excluding the expression and list set-up time. All tests were done on an Athlon XP 2000+ machine with 768MB of RAM. Results: GiNaC 1.0 --------- With default options: Binary tree, 2^N symbols.... N: 8 9 10 11 time/s: 0.17 1.33 13.269 129.4 Linear polynomial, N symbols...... N: 100 200 300 400 500 600 time/s: 0.13 1.39 6.32 18.539 49.429 109.64 With no_pattern = true: Binary tree, 2^N symbols.... N: 8 9 10 11 time/s: 0.17 1.31 12.29 129.629 Linear polynomial, N symbols...... N: 100 200 300 400 500 600 time/s: 0.08 1.03 4.879 15.429 41.77 99.43 GiNaC 1.0 wastes its time in the inefficient lst::op(). no_pattern isn't of much help here. GiNaC 1.1 --------- With default options: Binary tree, 2^N symbols..... N: 8 9 10 11 12 time/s: 0.01 0.05 0.17 0.739 5.06 Linear polynomial, N symbols...... N: 100 200 300 400 500 600 time/s: 0.05 0.4 1.34 3.149 6.15 10.92 With subs_options::subs_no_pattern: Binary tree, 2^N symbols..... N: 8 9 10 11 12 time/s: 0 0 0.029 0.17 2.25 Linear polynomial, N symbols...... N: 100 200 300 400 500 600 time/s: 0 0.04 0.1 0.25 0.479 0.81 Much better. subs_no_pattern significantly speeds up the second case. GiNaC 1.2 (i.e. what's currently in CVS) --------- Performs about 5% better than GiNaC 1.1 but shows the same scaling behavior, so I've omitted the results. GiNaC 1.2 with basic::subs() using a map<ex,ex,ex_is_less> instead of two lists --------- Default options: Binary tree, 2^N symbols..... N: 8 9 10 11 12 time/s: 0.01 0.029 0.13 0.55 3.899 Linear polynomial, N symbols...... N: 100 200 300 400 500 600 time/s: 0.059 0.39 1.29 3.12 5.919 10.46 With subs_options::subs_no_pattern: Binary tree, 2^N symbols..... N: 8 9 10 11 12 time/s: 0 0.01 0.029 0.13 1.53 Linear polynomial, N symbols...... N: 100 200 300 400 500 600 time/s: 0 0.02 0.04 0.059 0.1 0.149 A significant speedup, especially with subs_no_pattern. In the general case, subs() still has to iterate through the list of substitutions to apply match() to every single one. Only with subs_no_pattern can it use map::find(). But wait, there's more: I've noticed that expairseq::subschildren() scans the substitution list and uses a different algorithm depending on whether the list contains products or not. This step should be done only once, and the result passed on as a subs_options flag. Preliminary tests indicate that doing so speeds up the "binary tree" test by two orders of magnitude, and the "linear polynomial" test by 10%). Should these changes go into GiNaC 1.2? basic::normal() should then probably also be altered to take a map<> instead of two lists. What about match(), to_rational() and to_polynomial()? Also, this will break the API for class implementors (again), and Stefan Weinzierl will beat me. :-) (ok, it's broken in 1.2 anyway since basic::copy() and basic::destroy() are gone) Bye, Christian -- / Physics is an algorithm \/ http://www.uni-mainz.de/~bauec002/

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C++ code generation: any way of deflating large expressions?
by Dr. Vassilis S. Vassiliadis 10 Jul '03

10 Jul '03

I wonder if someone has run into the following and has found a easy way out: In generating C-source code from symbolic expressions it is always possible to run into trouble with large size expression output. For example, if one stores in an ex variable something like: ex SUM; `` SUM = \sum_{i=1}^{10000} x[i] ; '' then printing this out as csrc will generate a huge line. The best way is to see if there is an easy algorithmic construct (perhaps within GiNaC, or hints provided for its efficient implementation) so that at each level of the tree all operation-containing nodes are assigned a dummy variable (e.g. those of arithmetic operations or implementing a function). Then upon exhaustion, to reverse the procedure from the leaves of the tree to the root and thus generate a C++ code fragment with all necessary steps & intermediate variables to finally get the value of the root. ----------------------------------------------------------------- Dr. Vassilis S. Vassiliadis, Lecturer, UNIVERSITY OF CAMBRIDGE, DEPARTMENT OF CHEMICAL ENGINEERING Pembroke Street, Cambridge CB2 3RA, UK. Tel: (reception): +44 1223 334777 Fax: (departmental): +44 1223 334796 e-mail: vsv20(a)cheng.cam.ac.uk -----------------------------------------------------------------

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