Comment #11 on issue 3516 by [email protected]: gcd for Rationals is much slower than it should be
http://code.google.com/p/sympy/issues/detail?id=3516
From what I have been able to determine, when gcd is called on SymPy Rationals, it ends up with a call to igcd on numerators and ilcm on denominators (just what happens in _rgcd).
There are many function calls and these cause the gcd to perform bad IMO because the end procedure is the same as _rgcd. For example, 4 function calls to calculate numer and denom in case of Rationals.
In any case, the procedures for determining which gcd to use depends upon domain definitions in polys/domains/. I think that it would require too many changes, and would just cause more confusion later on, to just add an extra special case for Rationals. But that's just my opinion. If indeed in the long term we plan on increasing speed, I suppose we can have an implementation.
But, I believe it would require changing too many things and probably would break lots of things too. So, perhaps the EasyToFix label should be removed?
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