Yep. It's called cse(). Aaron Meurer
On Tuesday, June 7, 2016, Richard Fateman <[email protected]> wrote: > I think you are merely trying to find common subexpressions to speed up > evaluation. > There are lots of ways to do that. > The simplest is to precompute sin(t), cos(t), exp(t) or whatever > non-elementary > functions are involved. Then you can also consider using horner's rule or > something like factor. But there should be a common-subexpression > extraction > program around, no? > RJF > > > On Tuesday, June 7, 2016 at 11:39:20 AM UTC-7, brombo wrote: >> >> You might want to look at "New Foundations for Classical Mechanics" by >> David Hestenes and the rigid body rotor description of equations of motion. >> >> >> http://www.amazon.com/Foundations-Classical-Mechanics-Fundamental-Theories/dp/0792353021 >> >> Should be in your school library. >> >> >> >> On Tue, Jun 7, 2016 at 1:14 PM, Aaron Meurer <[email protected]> wrote: >> >>> On Tue, Jun 7, 2016 at 8:58 AM, Michi S <[email protected]> wrote: >>> > >>> > Thanks for the answers! For the purpose of my master thesis I am >>> trying to >>> > optimize the simulaion of helicopter dynamics. These dynamics are >>> pretty >>> > complicated, which leads to huge equations for most states. In order to >>> > speed up the calculation I need to detect functions that where already >>> > evaluated. The inner derivative that is produced due to the chain rule >>> is >>> > such a function, that I need to detect. >>> > >>> > factor() works only for the first derivative unfortunately. In the >>> second >>> > and higher derivatives it does not factorize the inner derivates >>> anymore: >>> > >>> > t = sym.symbols('t') >>> > diff( (sin(t)+exp(t))**5 , t ) >>> >>> (exp(t) + sin(t))**4*(5*exp(t) + 5*cos(t)) >>> > >>> > factor(diff( (sin(t)+exp(t))**5 , t )) >>> >>> 5*(exp(t) + sin(t))**4*(exp(t) + cos(t)) >>> > >>> > factor(diff( (sin(t)+exp(t))**5 , t, t )) >>> >>> 5*(exp(t) + sin(t))**3*(5*exp(2*t) + 8*exp(t)*cos(t) - sin(t)**2 + >>> >>> 4*cos(t)**2) >>> >>> What output were you expecting here? I don't think the second factor >>> can be factorized. Note however that it can be simplified slightly if >>> you call trigsimp() on it. >>> >>> Aaron Meurer >>> >>> > >>> > >>> > I think, writing my own differentiation programm will be a little bit >>> to >>> > hard to solve my issue. Is there no other way besides factor() and >>> wiriting >>> > my own programm? >>> > >>> > >>> > Thank for your help! >>> > >>> > >>> > Am Mittwoch, 1. Juni 2016 15:34:28 UTC+2 schrieb Michi S: >>> >> >>> >> Hello! >>> >> >>> >> Is there a way to turn off the automatic simplification by >>> calculating the >>> >> derivative of a function? For example >>> >> >>> >> t = sym.symbols('t') >>> >> sym.Derivative( (sin(t)+exp(t))**3 , t ).doit() >>> >> >>> >> gives: >>> >> (exp(t) + sin(t))**2*(3*exp(t) + 3*cos(t)) >>> >> >>> >> I need the result without any simplifications (in order to detect the >>> >> inner derivative for further calculations) >>> >> >>> >> Should be: >>> >> (exp(t) + sin(t))**2*3*(exp(t) + cos(t)) >>> > >>> > -- >>> > 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 https://groups.google.com/group/sympy. >>> > To view this discussion on the web visit >>> > >>> https://groups.google.com/d/msgid/sympy/c5e1f95e-d5e2-4334-b302-39bd6e2ebc9b%40googlegroups.com >>> . >>> > >>> > 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 https://groups.google.com/group/sympy. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/sympy/CAKgW%3D6J%3D%3Dq4K17wnEvJFagB3URSbJO9CHAjhDJ%3D6a6iQdbZ-gA%40mail.gmail.com >>> . >>> 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] > <javascript:_e(%7B%7D,'cvml','sympy%[email protected]');>. > To post to this group, send email to [email protected] > <javascript:_e(%7B%7D,'cvml','[email protected]');>. > Visit this group at https://groups.google.com/group/sympy. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/d5c4525a-207a-4561-8c8e-8ec397bef4c3%40googlegroups.com > <https://groups.google.com/d/msgid/sympy/d5c4525a-207a-4561-8c8e-8ec397bef4c3%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. 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