Hi Chris, Thanks for the kind words.
At the moment Matrix Expressions in the main branch do not use assumptions while simplifying. IIRC they actually used to but I removed it so that I could approach this more cleanly. One lofty reason for this was so that this could be used as a model for the rest of sympy when it eventually jumps over to the new assumptions system. If other devs see this e-mail - what are your thoughts on `refine`, the simplify API suggested (but rarely used) by new assumptions? Should we start using this? Should we roll it into simplify? In general at what point should we appeal to new assumptions? At expression creation time? At simplify time? At another simplify-like api time (e.g. refine time)? I decided not to call upon new assumptions while creating expressions (e.g. X.T creates a Transpose(X) even if X is symmetric). I think that my reasoning at the time was performance. Chris, in general what you're asking for is easy for us to add. I would like to make sure that we add it correctly. Also, it's been some time since this was all in my head. I may have said some untrue things. Best, -Matthew On Mon, Mar 17, 2014 at 4:57 PM, Chris <[email protected]> wrote: > Hi all, > > > I stumbled upon the discussion on matrix assumptions and the bit of > history behind this sympy module: > > http://scicomp.stackexchange.com/questions/74/symbolic-software-packages-for-matrix-expressions > > First off all, thank you Matt, this is incredibly cool stuff! > > Now, I'm trying to do some matrix algebra while encoding knowledge about > the matrices involved. For instance, say my matrix U is unitary, i.e. U * > U.T = I. I've looked around in the documentation and source code, but > couldn't figure out, if the new assumption system can be used to simplify > matrix expressions. > > I was trying to exploit this using sympy as follows: > > from sympy import Q, symbols, MatrixSymbol, ask, simplify > from sympy.assumptions.assume import global_assumptions > > n = symbols('n', integer=True) > U = MatrixSymbol('U', n, n) > > global_assumptions.add(Q.unitary(U)) > > UU = U * U.T > > print UU > > simpleUU = simplify(UU) > print simpleUU > > > I was hoping that the second print would output the Identity, but somehow > this didn't work. Any suggestions, pointers, hints? > > > Cheers, > Chris > > -- > 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/31aaea36-675d-40b0-8d77-aec8828f6c31%40googlegroups.com<https://groups.google.com/d/msgid/sympy/31aaea36-675d-40b0-8d77-aec8828f6c31%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/CAJ8oX-F0tjgppY2Am3zxy43gWKGfESjYDkVRwd%2BFfBgCgXw_2Q%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
