#15289: Implement indexed monoids
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Reporter: tscrim | Owner: sage-combinat
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-6.3
Component: algebra | Resolution:
Keywords: days54 | Merged in:
Authors: Travis Scrimshaw | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
public/monoids/15289-indexed | 1ff1a0483f5e61959a432371b701f593a5dee599
Dependencies: #15309, #15169 | Stopgaps:
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Comment (by SimonKing):
Replying to [comment:36 tscrim]:
> Simon, so I've changed the `UniqueFactory` object `FreeMonoid` to a new
factory function since it returns a class which I've designed as a
`UniqueRepresentation`. However unpickling old `FreeMonoid` objects fails
because of the unpickling mechanism of `UniqueFactory` redirects to
`generic_factory_unpickle()` and has `FreeMonoid` from the global
namespace as the first object.
First thing I wonder: ''Why'' is that statically typed? Just to shave off
a little calling overhead?
> It is expecting it to be a `UniqueFactory` instance, so it errors out
here. Furthermore because of the structure of the pickle, I'm unable to
use `register_unpickle_override` or see anyway to redirect that specific
pickle without changing the behavior of `generic_factory_unpickle()`.
I don't really understand how `register_unpickle_override` is working. It
seems that it can only work if `unpickle_global` is involved---and it is
not clear to me if this is involved everywhere or only if there is no
`__reduce__` method around.
> I'm thinking the best thing to do is to change
`generic_factory_unpickle()` to accept a general object as input and if
the first input is no longer a `UniqueFactory`, then call it with the
arguments given as part of the pickle.
Makes sense to me. And I even think the following idiom would not be
slower in terms of calling overhead than the current implementation:
{{{
def generic_factory_unpickle(factory, *args):
cdef UniqueFactory F
try:
F = factory
except TypeError:
return factory(*args[1:])
return F.get_objects(*args)
}}}
Note that I wrote `factory(*args[1:])`, since the first argument is the
version information. So, either we need to shave it off here, or the new
class (or function) replacing the old factory is required to take care of
this.
> I'm also thinking we should change this behavior so we don't keep
running into this problem.
I think with my suggestion above, unpickling of using factory would work
as quickly as it used to, and it would relatively easily allow to replace
the factory by something else (provided that this "something else" takes
care of the argument mangling and the version information that is involved
in the factory pickle).
--
Ticket URL: <http://trac.sagemath.org/ticket/15289#comment:44>
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