subs is slower and replace/xreplace should be used in places that need exact matches of sub-expressions or nodes.
There could be pitfalls if the code relies on the features of subs. Replacing the dummy symbols in linsolve sounds like a job for xreplace, not subs. I'm not sure why the matrix class doesn't have an xreplace method. My guess is we'd accept a pull request that adds one. Jason moorepants.info +01 530-601-9791 On Tue, Nov 17, 2015 at 7:50 PM, Jack Kemp <jack.kemp...@gmail.com> wrote: > On profiling my code I found it spent a lot of time in subs, particularly > the subs call at the end of linsolve where it substitutes in your given > free variables for the dummy parameters from gauss_jordan_solve. If I > replace subs with xreplace I get a 10x speedup in the substitution process > (250x without fastcache!). > > Are there any possible pitfalls in doing this? My understanding is the > advantage of subs over xreplace is that it is mathematically aware, so > (x**4).subs(x**2, y) will yield y**2 for example, while the same would not > work for xreplace. But if one is always replacing just a free symbol, such > as replacing the dummy symbol in linsolve, surely the two are equivalent? > If so, should linsolve just use xreplace? > > On the subject, why does the matrix class not have an xreplace method > which applies xreplace to its elements, like it has for subs? > > -- > 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 sympy+unsubscr...@googlegroups.com. > To post to this group, send email to sympy@googlegroups.com. > 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/da51f89a-b686-459d-a590-37049e42335d%40googlegroups.com > <https://groups.google.com/d/msgid/sympy/da51f89a-b686-459d-a590-37049e42335d%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 sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. 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/CAP7f1Agf47sdtH8W-s0VZ6EYXDQrq%2BvJuhfnr%2BcmeE3tt49JOw%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
