Ok, thanks :) On Fri, Jul 12, 2013 at 8:36 PM, Ondřej Čertík <[email protected]> wrote: > Hi Cristóvão, > > Excellent. Let us know if you need help with submitting a PR. > > Ondrej > > On Fri, Jul 12, 2013 at 1:32 PM, Cristóvão Sousa <[email protected]> wrote: >> Ok, I've added CSE of Add and Mul arguments (only commutative terms): >> http://nbviewer.ipython.org/5986996 >> >> It runs faster compared to current sympy.cse, even more if applying it to >> large expressions. >> However, it still lacks a lot of features, which I'll try to address using >> sympy.cse unit tests. >> >> >> On Wednesday, July 3, 2013 2:52:13 PM UTC+1, Cristóvão Sousa wrote: >>> >>> Forwarded from PyDy mailing list, >>> https://groups.google.com/forum/#!topic/pydy/PjZ9SP8PYDA . >>> >>> >>> >>> Hi, >>> >>> I'm posting here because of one of GSoC 2013 ideas, "Efficient Code >>> Generation". >>> >>> You stated that "Common subexpression elimination (cse) takes a long time >>> (>1 hour) to run on systems of equations that are derived in a very short >>> period of time (< 1 minute). This needs to be improved." >>> [https://pydy.org/gsoc_2013_ideas#efficient_code_generation] >>> >>> Indeed, I've verified that myself on my work on SymPyBotics >>> (https://github.com/cdsousa/sympybotics), a tool I'm developing to help me >>> on my PhD studies. >>> So, I've developed a kind of CSE, faster than SymPy CSE though less >>> general and with some quirks. >>> Such CSE functionality is implemented in SymCode package >>> (https://github.com/cdsousa/symcode). >>> >>> Be aware that both SymPyBotics and SymCode are badly documented and >>> probably reimplement some functionalities which could be taken from >>> SymPy/PyDy (and I probably implement them in worse ways :) >>> >>> The cse core function is "fast_cse()" which can be found in >>> symcode/subexprs.py >>> (https://github.com/cdsousa/symcode/blob/master/symcode/subexprs.py.) >>> (It uses Subexprs class, which can be used alone to store intermediate >>> variables in recursive computations). >>> >>> I've profiled SymPy cse and noticed that the main time consumption is due >>> to "count" and "subs" functions, so I tried a different approach. >>> First, fast_cse function reversely parses the expression tree and recreate >>> each unique operation with non-atom arguments substituted by temporary >>> symbols (this is the "collect" phase). >>> Each unique operation is stored on an "unique_op:tmp_symbol" dictionary. >>> For example, >>> a + b*c + cos(b*c) >>> is transformed into >>> t2 >>> while the dictionary holds >>> a + t0 + t1 : t2 >>> cos(t0) : t1 >>> b * c : t0 >>> Additional, match of multiple argument Mul and Add operations is made, in >>> a similar way to SymPy cse, although argument commutativity is always >>> assumed. >>> Then, in the "get" phase, the expression tree is recreated from the >>> dictionary while temporary "used more than once" symbols are maintained. >>> The example output will be >>> ( [(t0, b*c)], a + t0 + cos(t0) ) >>> This is much faster than SymPy CSE although output is generally different. >>> Also, it still doesn't work with "iterable" arguments, and, as said, >>> non-commutativity is not respected . >>> >>> >>> I would love to have time to work on this, or to work on SymPy CSE >>> optimization directly, but I'm currently in work overload. >>> Nevertheless, I'm showing you this since some ideas can be useful. >>> >>> Best regards, >>> Cristóvão Sousa >>> >> -- >> 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. >> For more options, visit https://groups.google.com/groups/opt_out. >> >> > > -- > You received this message because you are subscribed to a topic in the Google > Groups "sympy" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/sympy/mNsEVVLFVGU/unsubscribe. > To unsubscribe from this group and all its topics, 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. > For more options, visit https://groups.google.com/groups/opt_out. > >
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