This is typical behavior. Solving a 9 x 9 linear system will result in long expressions. If you want to print them it will take time to parse the tree because the expression is huge. Also, running the simplication routines on very large expressions will also take a long time and may never even finish depending on your computer's specs, the algorithm, etc.
Jason moorepants.info +01 530-601-9791 On Tue, Sep 2, 2014 at 10:42 AM, gundamlh <[email protected]> wrote: > Hi Aaron, > > I use Sympy to compute the solution of an inverse problem (Ax = b) > symbolically, where A is a 9-by-9 symbolic matrix. The computation is quite > fast, however the out-printing of the solution ''x'' vector is very slow, > even the first entry x[0] takes longer than 2 minutes. And the > sympy.ratsimp(x[0]) is also very slow.. I am confused... > > Hope for your kind response. Thanks in advance! > Hong > > > > 在 2012年3月4日星期日UTC+1下午9时49分06秒，Aaron Meurer写道： >> >> On Wed, Feb 29, 2012 at 9:28 AM, Vinzenz Bargsten <[email protected]> >> wrote: >> > Am 28.02.2012 06:41, schrieb Ondřej Čertík: >> > >> >> Hi Vinzenz, >> >> >> >> On Mon, Feb 27, 2012 at 4:27 PM, Vinzenz Bargsten<[email protected]> >> >> wrote: >> >> [...] >> >>> >> >>> Thank you very much. I think I get the point, but I will need some >> time >> >>> to >> >>> implement it. >> >>> If this is working, I can finally get rid of Mathematica and the >> complete >> >>> modeling procedure as well as the required model transformations >> >>> for a 7-axes robot (Kuka LWR) are carried out by sympy. >> >> >> >> That'd be really cool. Yes, the trigonometric simplification is pretty >> >> hard. >> >> Besides that, how is SymPy doing otherwise in terms of speed compared >> >> to Mathematica for your problem? >> >> >> >> >> >> Ondrej >> > >> > Hi Ondrej, >> > >> > your question is not easy to answer. It depends on the actual task and >> how >> > you implement it / the algorithm. The simplification problem is an >> example: >> > Using the expand()-replace()-solution is probably slower compared to >> > Mathematica's Simplify[], but using the monomial-based solution may be >> > faster. >> > On average, I would say sympy is at least as fast as Mathematica for my >> > application. >> >> Well, in general, you should be able to just call simplify() (or >> trigsimp()), and it should just work. So simplification (especially >> trig simplification) is one area where we can definitely use >> improvement. >> >> > >> > The advantages of sympy in my eyes compared to Mathematica are that >> sympy is >> > deterministic and you get error messages and the messages point to the >> > problem. >> >> This is the first time I've heard this particular reason for SymPy >> being better. How is Mathematica non-deterministic? I've never used >> it, except for WolframAlpha, because, as you noted, it's not free, and >> I don't own a copy. >> >> I suppose the better error messages are a result of Python including >> the traceback? >> >> > Besides the math functions (in many cases superior or unique) >> >> Cool. What functions are unique? I only know of one that I'm pretty >> sure is unique (or at least I couldn't find it in their docs), but >> it's part of the polys module. I guess maybe the code generation >> stuff? >> >> > it >> > has many convenient functions (such as the printing functions to >> generate >> > c-code of your expressions) and one can use all other python functions. >> -- >> > and sympy is free ;) >> > >> > Regards, >> > Vinzenz >> >> Aaron Meurer >> >> -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/sympy. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/65cd2d04-84ff-4eac-8a69-93c144061d83%40googlegroups.com > <https://groups.google.com/d/msgid/sympy/65cd2d04-84ff-4eac-8a69-93c144061d83%40googlegroups.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/CAP7f1Ahie8z6jX_%3DkXYNaD9BnP9o5ReUV9tz58xgmqB3pf%3D4jQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
