#13589: Controlling C3 to solve once for all the Method Resolution Order issues
for
category classes
----------------------------------------------------------+-----------------
Reporter: nthiery | Owner:
nthiery
Type: defect | Status:
needs_review
Priority: major | Milestone:
sage-5.11
Component: categories | Resolution:
Keywords: method resolution order, C3 | Work issues:
Report Upstream: N/A | Reviewers:
Simon King, Florent Hivert
Authors: Nicolas M. Thiéry | Merged in:
Dependencies: #12894, #12876, #11935, #12895, #10193 | Stopgaps:
----------------------------------------------------------+-----------------
Comment (by SimonKing):
In the computation of _cmp_key, it says:
{{{
atoms = ("FacadeSets", "Finite", "Infinite", "EnumeratedSets",
"FiniteDimensionalModulesWithBasis", "GradedModules", "ModulesWithBasis",
"AdditiveMagmas", "Magmas", "Semigroups", "Monoids",
"FinitePermutationGroups", "Rngs", "Domains")
classname = self.__class__.__name__
flag = 0
for i, axiom in enumerate(atoms):
if classname.startswith(axiom):
flag = flag | (1 << i)
}}}
First a Python question: Will the tuple `atoms` be constructed repeatedly
in this method? If this is the case, it might be better to move it to
module level.
Second question: With the exception of "Finite" and
"FiniteDimensionalModulesWithBases", the atoms are pairwise incompatible,
in the sense of "if classname starts with one of the atoms, then it will
certainly not start with any other atom". Hence, it seems possible to
rewrite it such that the `for` loop is quit after the first case in which
the `if` clause is true.
But again, probably a speed gain in a method that is called only once will
be negligible.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13589#comment:56>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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