Cythoned UniqueRepresentation

simon-king-jena commented 11 years ago

UniqueRepresentation provides a comfortable way to create unique parent structures, and automatically provides a hash and certain comparison methods.

Problems:

It relies on a metaclass, namely ClasscallMetaclass and thus has to be a Python class. That's bad for speed.
It combines two features, namely a cache and unique instance behaviour. But in many some cases we want a cache so that two distinct instances can still be equal.

Here, I suggest to

separate the two features, by creating a new class sage.unique_representation.CachedRepresentation as one base of UniqueRepresentation.
create a new cdef class sage.misc.fast_methods.WithRichCmpById, that provides hash and rich comparison, as expected for unique instance behaviour.

Apply

Depends on #14017 Depends on #6495 Depends on #14182 Depends on #14040 Depends on #14011

CC: @nthiery

Component: performance

Keywords: cython UniqueRepresentation

Author: Simon King

Reviewer: Travis Scrimshaw

Merged: sage-5.8.beta4

Issue created by migration from https://trac.sagemath.org/ticket/14054

simon-king-jena commented 11 years ago

Attachment: trac_14054_cythoned_unique_representation.patch.gz

simon-king-jena commented 11 years ago

comment:1

Note that the patch also needed to change some auxiliary class CartanType_simple_finite, which is used to unpickle some old data. It used to inherit from object, but for an incompatibility of Cython types it has to inherit from UniqueRepresentation instead.

For the timings, I use MatrixSpace, which inherits from UniqueRepresentation:

sage: isinstance(MatrixSpace(GF(3),2,3), UniqueRepresentation)
True

With sage-5.6.rc0 plus #14017:

sage: %time L = [MatrixSpace(GF(3),n) for n in range(10000)]
CPU times: user 1.94 s, sys: 0.05 s, total: 2.00 s
Wall time: 2.00 s
sage: %time D = dict(zip(L,range(len(L))))
CPU times: user 0.01 s, sys: 0.00 s, total: 0.01 s
Wall time: 0.01 s
sage: MS = MatrixSpace(GF(3),10000)
sage: MS in D
False
sage: timeit("MS in D", number = 10^6)
1000000 loops, best of 3: 552 ns per loop
sage: MS = L[5000]
sage: MS in D
True
sage: timeit("MS in D", number = 10^6)
1000000 loops, best of 3: 540 ns per loop

Adding the patch from here:

sage: %time L = [MatrixSpace(GF(3),n) for n in range(10000)]
CPU times: user 1.96 s, sys: 0.04 s, total: 2.00 s
Wall time: 2.00 s
sage: %time D = dict(zip(L,range(len(L))))
CPU times: user 0.01 s, sys: 0.00 s, total: 0.01 s
Wall time: 0.01 s
sage: MS = MatrixSpace(GF(3),10000)
sage: MS in D
False
sage: timeit("MS in D", number = 10^6)
1000000 loops, best of 3: 187 ns per loop
sage: MS = L[5000]
sage: MS in D
True
sage: timeit("MS in D", number = 10^6)
1000000 loops, best of 3: 176 ns per loop

Hence, the time drops by 2/3. I did run make ptest successfully. Needs review!

simon-king-jena commented 11 years ago

comment:2

Cc to Nicolas as the original author of UniqueRepresentation.

simon-king-jena commented 11 years ago

comment:3

I just did some experiments with the tp_hash function from Python's C-API: It is 1/3 faster than a cythoned hash. I'll try to do similar things with the comparison methods.

simon-king-jena commented 11 years ago

comment:4

While we are at speeding up UniqueRepresentation, I think we should actually refactor it. Namely, UniqueRepresentation serves two purposes, namely (1) caching, and (2) comparison and hash by identity.

Some classes misuse UniqueRepresentation by only using feature (1), overriding comparison in a way that violates the unique representation condition. See my monologue at sage-devel.

I suggest to split the two features.

simon-king-jena commented 11 years ago

comment:5

FWIW, I finished a more experimental and rather intrusive version of UniqueRepresentation.

Idea:

Create a cdef function, that results in faster C code than what Cython makes of
```
def __hash__(self):
  return id(self)
```
Override tp_hash with this function, for every instance of UniqueRepresentation. Likewise for tp_richcompare.

It remains possible to override those parts of comparison that can't be decided by looking at identity (such as "a<b" if "a is not b").

It would be great to just define the fast hash and comparison for UniqueRepresentation itself, but alas it seems that subclasses forget these settings, whether they override __hash__ or not. See the comments on sage-devel.

I still think it is a good idea to separate UniqueRepresentation from CachedRepresentation, but I am not so sure about enforcing the uniqueness behaviour, without the possibility to override it---this wouldn't be pythonic...

Let the patchbot do some work:

Apply trac14054_fast_methods.patch

simon-king-jena commented 11 years ago

comment:6

From sage-devel, I understand that people think that separating the cache feature from the uniqueness feature of UniqueRepresentation is a good idea.

However, in my old patch, I was enforcing uniqueness behaviour for instances of UniqueRepresentation. This isn't pythonic. Hence, I do differently in the new patch version.

Question

In the current implementation, inheritance from UniqueRepresentation will overload rich comparison (==, >=, !=, etc.) inherited from a base class, but it will not overload comparison (cmp). Do you think that both should be overloaded?

Patchbot reported two failures with the previous patch version. I guess that's because of an additional dependency. So, as soon as I have a decent internet connection, I'll download the latest beta, and rebase on top of it.

Apply trac14054_fast_methods.patch

simon-king-jena commented 11 years ago

comment:7

Other question: Does provide_hash_by_id really make sense to have?

simon-king-jena commented 11 years ago

comment:8

The updated patch should make the coverage script happy, but three tests with 5.7.rc0 currently fail. I am downloading 5.7.rc0 now.

Apply trac14054_fast_methods.patch

b03034c9-f2cf-4d37-9a1e-419dd712df02 commented 11 years ago

comment:9

I am not qualified to look over this ticket, but glancing at it I spotted this

308         complete = complete = self.complete()

which looks like a typo.

simon-king-jena commented 11 years ago

comment:10

Replying to @sagetrac-jlopez:

I am not qualified to look over this ticket, but glancing at it I spotted this
308           complete = complete = self.complete() 
which looks like a typo.

Yes, thank you for spotting it! Will remove it when I rebase the patch against 5.7.rc0.

tscrim commented 11 years ago

comment:11

Hey Simon,

Let me know when this is ready for review again.

Best,

Travis

tscrim commented 11 years ago

Reviewer: Travis Scrimshaw

simon-king-jena commented 11 years ago

comment:12

The patch should now be ready for review.

Two questions that I'd like to have addressed:

I introduce provide_hash_by_id, but I don't use it. Shall it be deleted?
Is it enough to override the rich comparison methods? Currently, one can have hash(a)!=hash(b) but cmp(a,b)==0. Does this violate the contract of hash functions? Or is it enough that hash(a)!=hash(b) implies a!=b?

Pathbot:

Apply trac14054_fast_methods.patch

simon-king-jena commented 11 years ago

Description changed:

--- 
+++ 
@@ -1,5 +1,15 @@
-`UniqueRepresentation` provides a comfortable way to create unique parent structures, and automatically provides a hash and certain comparison methods. Problem: It relies on a metaclass, namely `ClasscallMetaclass` and thus has to be a Python class. That's bad for speed.
+`UniqueRepresentation` provides a comfortable way to create unique parent structures, and automatically provides a hash and certain comparison methods.

-Here, I suggest to create a new cdef class `UniqueRepresentation_c` that provides hash and comparison, and let `UniqueRepresentation` inherit from it, just adding the classcall method.
+Problems:

-The problem is that `UniqueRepresentation` relies on cached_method, and this decorator had problems to work on methods defined in Cython with varargs and keywords arguments. That is fixed in #14017, which is thus a dependency.
+- It relies on a metaclass, namely `ClasscallMetaclass` and thus has to be a Python class. That's bad for speed.
+- It combines two features, namely a cache and unique instance behaviour. But in many some cases we want a cache so that two distinct instances can still be equal.
+
+Here, I suggest to 
+
+1. separate the two features, by creating a new class `sage.unique_representation.CachedRepresentation` as one base of `UniqueRepresentation`.
+2. create a new cdef class `sage.misc.fast_methods.WithRichCmpById`, that provides hash and rich comparison, as expected for unique instance behaviour.
+
+__Apply__
+
+- [attachment: trac14054_fast_methods.patch](https://github.com/sagemath/sage-prod/files/10657049/trac14054_fast_methods.patch.gz)

simon-king-jena commented 11 years ago

comment:13

To answer the question about the hash contract:

Apparently dictionaries use the rich comparison methods and not cmp:

sage: class Bla(object):
....:     def __hash__(self):
....:         return 2
....:     def __cmp__(self, other):
....:         return 0
....:     def __eq__(self, other):
....:         return self is other
....:     def __ne__(self, other):
....:         return self is not other
....:     
sage: a = Bla()
sage: b = Bla()
sage: a==b
False
sage: hash(a)==hash(b)
True
sage: cmp(a,b)
0
sage: D = {a:1}

Since hash(a)==hash(b), a and b belong to the same hash bucket of the dictionary. And comparison by cmp tells that they are equal. But we still have:

sage: D[b]
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-8-6cf1ee6b63d5> in <module>()
----> 1 D[b]

KeyError: <__main__.Bla object at 0x5064310>

Hence, dictionaries use comparison by ==, and thus my patch does the right thing, IMHO.

nbruin commented 11 years ago

comment:14

Replying to @simon-king-jena:

I introduce provide_hash_by_id, but I don't use it. Shall it be deleted?

Yes, you should. I'm pretty sure changing type->tp_hash after calling PyType_Ready() is not supported by the Python C-API (see the inheritance problems we saw).

Is it enough to override the rich comparison methods? Currently, one can have hash(a)!=hash(b) but cmp(a,b)==0.

Does this violate the contract of hash functions? Or is it enough that hash(a)!=hash(b) implies a!=b?

I think Python requires hash(a)!=hash(b) implies not(a==b), which Python does not enforce to be the same thing. In any case, I'm pretty sure that "rich comparison" is fully exhausted before trying to use __cmp__, which is only there because of backward compatibility.

There's another peculiarity for membership and lookup in python:

sage: class neq(object):
....:     def __eq__(self,other):
....:         return False
....:     def __ne__(self,other):
....:         return True
....:     
sage: a=neq()
sage: V={a}
sage: a in V
True
sage: sage: [a == v for v in V]
[False]

They explicitly mention this in the documentation: because hash collisions are rare, they first test "is" for dict lookup before trying "==" (it's cheaper).

simon-king-jena commented 11 years ago

comment:15

Replying to @nbruin:

Replying to @simon-king-jena:

I introduce provide_hash_by_id, but I don't use it. Shall it be deleted?

Yes, you should.

OK.

Does this violate the contract of hash functions? Or is it enough that hash(a)!=hash(b) implies a!=b?

I think Python requires hash(a)!=hash(b) implies not(a==b),

Right, that's a difference.

In any case, I'm pretty sure that "rich comparison" is fully exhausted before trying to use __cmp__, which is only there because of backward compatibility.

Nope! See my post on sage-devel.

If you have a non-cdef class, then it seems __richcmp__ is simply ignored (but methods like __eq__ have precedence over __cmp__). In a cdef class, __richcmp__ has priority over __cmp__ when deciding binary relations such as ==, <, <=, etc. But for cmp(,), __cmp__ will be used, even if there is __richcmp__!

So, the decisive question is: Do dictionaries compare stuff by cmp(a,b)==0 or by a==b?

It is the latter, and thus making __richcmp__ compatible with __hash__ was the right thing to do.

For now, it needs work, because I will delete the C API hack, and apparently some script of the patchbot has a complaint...

simon-king-jena commented 11 years ago

Attachment: trac14054_fast_methods.patch.gz

Separate cache and uniqueness.

simon-king-jena commented 11 years ago

comment:16

Done!

It seems that the patchbot complains about an increased startup time. How did that happen? Is it because of a slightly longer mro for UniqueRepresentation?

Patchbot:

Apply trac14054_fast_methods.patch

nbruin commented 11 years ago

comment:17

What's your rationale to define 'a < b' etc. when a is b? I agree that it's likely that your answers are what any ordering override will want, but Python does not mandate any particular properties of semantics of these operators. So I think the proper thing is to just not do anything there. It's going to be a rare occasion anyway, so a little speed gain won't be very noticeable anyway.

The behaviour you are implementing is much easier to explain if you don't override those cases: Then you can just say that WithRichCmpById provides __hash__, __eq__ and __ne__, period.

I think WithEqualityById would make a better conceptual name that is less dependent on the implementation, by the way. Your motivation here seems to be as much to provide conceptual units in preference of just technical implementation tools as to provide more efficient implementations. Someone writing a Python class may not know what "richcomp" is, and doesn't need to.

tscrim commented 11 years ago

comment:18

Hey,

Replying to @nbruin:

What's your rationale to define 'a < b' etc. when a is b? I agree that it's likely that your answers are what any ordering override will want, but Python does not mandate any particular properties of semantics of these operators. So I think the proper thing is to just not do anything there. It's going to be a rare occasion anyway, so a little speed gain won't be very noticeable anyway.

So how would you want comparisons in the complex numbers to behave? In python, they return an error:

sage: complex(2+2*i) < complex(2-2*i)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-2-ce2e269601f6> in <module>()
----> 1 complex(Integer(2)+Integer(2)*i) < complex(Integer(2)-Integer(2)*i)

TypeError: no ordering relation is defined for complex numbers

However in sage they are not so well-behaved (see #14088):

sage: CC(1+2*i) < CC(2-2*i)
True

so there's no prescribed sage way.

As far as the actual comparison code, I think it would be better to do something like

if m == 2:
    return True
elif m == 3:
    return False
else:
    return m == 1 or m == 5

but this is a micro-optimization, so feel free to ignore this.

The behaviour you are implementing is much easier to explain if you don't override those cases: Then you can just say that WithRichCmpById provides __hash__, __eq__ and __ne__, period.

I think WithEqualityById would make a better conceptual name that is less dependent on the implementation, by the way. Your motivation here seems to be as much to provide conceptual units in preference of just technical implementation tools as to provide more efficient implementations. Someone writing a Python class may not know what "richcomp" is, and doesn't need to.

I believe the response to both of these points depends on how we want to do comparison between objects (when there is not a [natural] ordering).

Last thing for now, shouldn't we issue a deprecation warning for FastHashable_class since it has changed locations?

Thanks,

Travis

nbruin commented 11 years ago

comment:19

The issue is that if someone wants to define

class C(WithEqualityById):
    def __cmp__(self,other):
        return -1

they will find that

sage: a=C()
sage: a < a
False

which might surprise them, because they thought that WithEqualityById only affected (in)equality testing and let ordering comparisons fall through to __cmp__ if implemented. With the current code, this is not the case if the two arguments are identical.

There have been extensive discussions about what inequality testing SHOULD be in sage and for the most part the implementation here is staying clear of the topic (which I think is a good thing). There's just this one small optimization that's probably usually OK, but if left out makes for much more predictable behaviour.

simon-king-jena commented 11 years ago

comment:20

Replying to @nbruin:

What's your rationale to define 'a < b' etc. when a is b? I agree that it's likely that your answers are what any ordering override will want, but Python does not mandate any particular properties of semantics of these operators.

Python does not. But I think "comparison by identity" implies a semantics. And that is: a < a is False, a <= a is True.

The behaviour you are implementing is much easier to explain if you don't override those cases: Then you can just say that WithRichCmpById provides __hash__, __eq__ and __ne__, period.

OK.

I think WithEqualityById would make a better conceptual name that is less dependent on the implementation, by the way.

Good idea.

Replying to @tscrim:

Last thing for now, shouldn't we issue a deprecation warning for FastHashable_class since it has changed locations?

I think I introduced it. But when? Or what ticket? I don't think anyone used it.

simon-king-jena commented 11 years ago

comment:21

Replying to @simon-king-jena:

The behaviour you are implementing is much easier to explain if you don't override those cases: Then you can just say that WithRichCmpById provides __hash__, __eq__ and __ne__, period.

OK.

I think WithEqualityById would make a better conceptual name that is less dependent on the implementation, by the way.

Good idea.

Note: I would not like the name "WithCmpById", because cmp relies on __cmp__ (which is not touched) even if __richcmp__ exists.

Replying to @tscrim:

Last thing for now, shouldn't we issue a deprecation warning for FastHashable_class since it has changed locations?

I think I introduced it. But when? Or what ticket? I don't think anyone used it.

It was in #11900. We could of course keep it in sage.categories.category_singleton, but I think that's not the right place. Note that I remove the dependency of CategorySingleton on FastHashable_class, because the new cythoned hash is slightly faster.

simon-king-jena commented 11 years ago

comment:22

This will not go into 5.7 anyway. Hence, I was rebasing against #6495 (which is a minor change anyway). In addition, I took into account your comments:

I rename the new class into WithEqualityById.
I move FastHashable_class back into category_singleton (wrong as this may be...)

I hope this addresses all complaints.

Apply trac14054_fast_methods-5.8.patch

simon-king-jena commented 11 years ago

Changed dependencies from #14017 to #14017, #6495

simon-king-jena commented 11 years ago

Description changed:

--- 
+++ 
@@ -12,4 +12,4 @@

 __Apply__

-- [attachment: trac14054_fast_methods.patch](https://github.com/sagemath/sage-prod/files/10657049/trac14054_fast_methods.patch.gz)
+- [attachment: trac14054_fast_methods-5.8.patch](https://github.com/sagemath/sage-prod/files/10657050/trac14054_fast_methods-5.8.patch.gz)

simon-king-jena commented 11 years ago

comment:23

Oops, I forgot to rename two occurrences of WithRichCmpById into WithEqualityById...

Should now pass all tests.

Apply trac14054_fast_methods-5.8.patch

simon-king-jena commented 11 years ago

comment:24

Strange. I can not replicate the error reported by the patchbot.

tscrim commented 11 years ago

comment:25

Neither can I by hand or testing the individual files. It has to be something since the testbot can reproduce it... Have you tried running testall by chance? I ran tests in the categories folder than on free_module.py and that passed.

It must have something to testing things in the right order...I'm wondering if the problem lies with free_module.tensor_constructor() being a cached_method and something is being improperly stored...

simon-king-jena commented 11 years ago

comment:26

Replying to @tscrim:

It must have something to testing things in the right order...I'm wondering if the problem lies with free_module.tensor_constructor() being a cached_method and something is being improperly stored...

The failing assertion is

      File "/mnt/storage2TB/patchbot/Sage/sage-5.8.beta0/local/lib/python/site-packages/sage/categories/modules_with_basis.py", line 1387, in __call__
        assert(x.parent() is self.domain())

I can hardly imagine that there is yet another premature deallocation via weak references in play. After all, both x._parent and self._domain are just plain strong references.

nbruin commented 11 years ago

comment:27

This parent mismatch happens in a morphism call. If a morphism gets registered in the wrong slot in a conversion/coercion then it could indeed end up getting mismatched input (shouldn't __call__ be a little more permissive about its arguments by the way? Certainly, an error would be more appropriate than an assert if this is something that actually can go wrong)

Anyway, TripleDict does store homomorphisms and we've recently seen it's not entirely safe wrt. garbage collections that can happen during update procedures. That can cause homomorphisms to get registered under the wrong domain/codomain keys.

I think it's extremely unlikely that this is happening in this particular situation, but if all other conceivable alternatives are impossible ... (since the corruption would be dependent on a GC happening at just the wrong time, it would be extremely fickle behaviour that is very hard to reproduce).

Of course, if this test is using a map that wasn't retrieved from a TripleDict or a MonoDict the above explanation is impossible.

simon-king-jena commented 11 years ago

comment:28

Replying to @nbruin:

This parent mismatch happens in a morphism call. If a morphism gets registered in the wrong slot in a conversion/coercion then it could indeed end up getting mismatched input

If it is in a wrong slot (you mean: Addressed by a non-identic copy of a parent?) then it should simply not occur here, because TripleDict would compare by identity.

(shouldn't __call__ be a little more permissive about its arguments by the way? Certainly, an error would be more appropriate than an assert if this is something that actually can go wrong)

No, I think an assertion is the right thing to do here. Perhaps one could provide the assertion with an error message that names the two parents that don't match. In that way, we could at least see what two parents are involved.

Note that my patch changes CombinatorialFreeModule from UniqueRepresentation to CachedRepresentation, since it overrides the equality tests. So, it could actually be that the two parents are genuinely non-unique. And since a cached_method is involved here, which does comparison by equality and not identity, we could really be in trouble here.

Of course, it could be that changing to CachedRepresentation was wrong in this case.

nbruin commented 11 years ago

comment:29

Replying to @simon-king-jena:

If it is in a wrong slot (you mean: Addressed by a non-identic copy of a parent?) then it should simply not occur here, because TripleDict would compare by identity.

No, what I meant is: bucket position to write value into gets determined, dictionary gets changed due to a GC, value gets placed into bucket position determined earlier, which now belongs to an entirely different key triple. Without #13387 we couldn't strictly exclude that from happening, but it would need extreme bad luck.

Your hypothesis sounds much more probable.

simon-king-jena commented 11 years ago

comment:30

By the way: One reason for removing FastHashable_class from sage.categories.category_singleton is the fact that the hash inherited from the cythoned version of UniqueRepresentation is faster than what was provided by FastHashable_class.

tscrim commented 11 years ago

comment:31

Replying to @simon-king-jena:

By the way: One reason for removing FastHashable_class from sage.categories.category_singleton is the fact that the hash inherited from the cythoned version of UniqueRepresentation is faster than what was provided by FastHashable_class.

I didn't want it to not be removed, but I thought it was suppose to have a deprecation warning saying the class had moved/changed namespaces?

simon-king-jena commented 11 years ago

comment:32

Replying to @tscrim:

I didn't want it to not be removed, but I thought it was suppose to have a deprecation warning saying the class had moved/changed namespaces?

Would you mind to just leave it in its original space (being an orphan, though)?

Otherwise: How does one deprecate a class that has no init method?

simon-king-jena commented 11 years ago

comment:33

Replying to @simon-king-jena:

Otherwise: How does one deprecate a class that has no init method?

"Had" no init method, I should say.

Anyway, if I move it to a different file, then the import statement "from sage.categories.category_singleton import FastHashable_class" should result in a deprecation warning. How can this be achieved?

simon-king-jena commented 11 years ago

comment:34

Let's test whether the safer use of callbacks for weak references to Homsets stored in a TripleDict from #14159 will fix the problem here.

Apply https://github.com/sagemath/sage-prod/files/10657050/trac14054_fast_methods-5.8.patch.gz

simon-king-jena commented 11 years ago

Changed dependencies from #14017, #6495 to #14017, #6495, #14159

simon-king-jena commented 11 years ago

comment:35

Patchbot,

Apply trac14054_fast_methods-5.8.patch

simon-king-jena commented 11 years ago

comment:36

Hooray, I can reproduce the assertion error (it only occurs with the patch from here)! So, that should make it possible to debug it.

tscrim commented 11 years ago

comment:37

Replying to @simon-king-jena:

Would you mind to just leave it in its original space (being an orphan, though)?

Otherwise: How does one deprecate a class that has no init method?

What I've done is turned the class into a function and have that function return the desired class after issuing the deprecation warning. I guess an alternative would be to implement a custom __call__ which does the same as above.

How are you reproducing the assertion error?

simon-king-jena commented 11 years ago

comment:38

Replying to @tscrim:

How are you reproducing the assertion error?

By running ./sage -t -force_lib devel/sage/sage/combinat/free_module.py with sage-5.8.beta0 plus #12313, #13387, #14159 and #14054.

simon-king-jena commented 11 years ago

comment:39

Replying to @tscrim:

Replying to @simon-king-jena: What I've done is turned the class into a function and have that function return the desired class after issuing the deprecation warning.

Perhaps like this:

            sage: from sage.misc.superseded import deprecated_function_alias
            sage: g = deprecated_function_alias(13109, number_of_partitions)

simon-king-jena commented 11 years ago

comment:40

I hesitate to do things like

from sage.misc.superseded import deprecated_function_alias
from sage.misc.fast_methods import FastFashable_class as FH_class
FastHashable_class = deprecated_function_alias(14054,FH_class)

in sage.categories.category_singleton:

It adds an unneeded import statement
FastHashable_class is a base class, and hence one would like to inherit from it. But doing the above, FastHashable_class would not be a class but a function in sage.categories.category_singleton.
In its now deprecated use, it was necessary to cimport (not just import!) the class. That will be impossible, no matter what way of deprecation warning we use, because deprecation warnings won't work at compile time.

Is there a "lazy import statement with deprecation"? Then, one would not actually import FastHashable_class in category_singleton, but from sage.categories.category_singleton import FastHashable_class would result in a deprecation warning. And we can't cope with the compile time cimport problem anyway.

tscrim commented 11 years ago

comment:41

Replying to @simon-king-jena:

Perhaps like this:

            sage: from sage.misc.superseded import deprecated_function_alias
            sage: g = deprecated_function_alias(13109, number_of_partitions)

That might work, but I haven't tried it (in principle, I don't see why it wouldn't). What I've done is like this:

def DeprecatedClass(self, arg1, arg2, ..., *old_args, **old_kwds):
    from sage.misc.superseded import deprecation
    deprecation(14054, "DepC is deprecated. Use path.to.new_mod.NewClass instead")
    # Do whatever needs to be done to convert to NewClass's inputs
    from path.to.new_mod import NewClass
    return NewClass(arg1, arg2, ..., *old_args, **old_kwds)

However that's a good point about the inheritance...perhaps something like

class Dep(NewClass):
    def __init__(self, arg1, arg2, ..., *args, **kwds):
        from sage.misc.superseded import deprecation
        deprecation(14054, "DepC is deprecated. Use path.to.new_mod.NewClass instead")
        NewClass.__init__(self, arg1, arg2, ..., *args, **kwds)

?

simon-king-jena commented 11 years ago

comment:42

Replying to @tscrim:

However that's a good point about the inheritance...perhaps something like

class Dep(NewClass):
    def __init__(self, arg1, arg2, ..., *args, **kwds):
        from sage.misc.superseded import deprecation
        deprecation(14054, "DepC is deprecated. Use path.to.new_mod.NewClass instead")
        NewClass.__init__(self, arg1, arg2, ..., *args, **kwds)

?

Well, that would still mean that we need to actually import it.

I am tempted to ask what sage-devel has to say about this issue.

tscrim commented 11 years ago

comment:43

Replying to @simon-king-jena:

Well, that would still mean that we need to actually import it.

I thought if we turn it into a python class, we wouldn't need to cimport it and it would only be imported if the old class was actually used? (To me honest, part of me is still wondering if we even really need a deprecation warning since it is such a low-level base class.)

I am tempted to ask what sage-devel has to say about this issue.

That might be for the best.

sagemath / sage

Cythoned UniqueRepresentation #14054