Opened 11 years ago
Closed 8 years ago
#5970 closed defect (duplicate)
Weak references in Polynomial Ring cache
Reported by: | SimonKing | Owned by: | malb |
---|---|---|---|
Priority: | critical | Milestone: | sage-duplicate/invalid/wontfix |
Component: | commutative algebra | Keywords: | polynomial ring cache weak reference |
Cc: | jpflori, zimmerma, vbraun | Merged in: | |
Authors: | Reviewers: | Simon King | |
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description (last modified by )
At http://groups.google.com/group/sage-support/browse_thread/thread/ef01dae47c835137 a memory leak was reported.
Reason for the leak: Many different polynomial rings are created, but used only once. But since we want to have unique parents, they are all cached and thus prevented from deletion.
As Robert pointed out, using weak references enables us to both have unique parents and garbage collection.
With the patch, that should at least apply to sage 3.4.1.rc3, one can do
sage: for p in primes(2,1000000): ....: R.<x,y,z> = GF(p)[]
without running into memory problems.
See instead #715.
Attachments (3)
Change History (38)
Changed 11 years ago by
comment:1 follow-up: ↓ 3 Changed 11 years ago by
- Milestone changed from sage-3.4.2 to sage-4.0
- Summary changed from [with patch, needs review] Weak references in Polynomial Ring cache to [with patch, needs work] Weak references in Polynomial Ring cache
Ooops, but this does seem to expose some problems:
sage -t -long devel/sage/sage/rings/number_field/number_field.py # Segfault sage -t -long devel/sage/sage/rings/tests.py # Segfault sage -t -long devel/sage/sage/rings/number_field/number_field_rel.py # Segfault sage -t -long devel/sage/sage/rings/number_field/number_field_element.pyx # Segfault sage -t -long devel/sage/sage/rings/residue_field.pyx # Segfault sage -t -long devel/sage/sage/rings/number_field/number_field_ideal_rel.py # Segfault sage -t -long devel/sage/sage/rings/number_field/morphism.py # Segfault sage -t -long devel/sage/sage/rings/polynomial/polynomial_singular_interface.py # Segfault sage -t -long devel/sage/sage/rings/number_field/unit_group.py # Segfault sage -t -long devel/sage/sage/rings/number_field/small_primes_of_degree_one.py # Segfault sage -t -long devel/sage/doc/en/bordeaux_2008/nf_orders.rst # Segfault sage -t -long devel/sage/sage/rings/number_field/maps.py # Segfault sage -t -long devel/sage/sage/schemes/generic/affine_space.py # Segfault
And something this low level will definitely not go into 3.4.2 at this stage.
Cheers,
Michael
comment:2 Changed 11 years ago by
In case this might help somebody working on this, I've attached a small file with test functions for checking the memory usage for loops with elliptic curve, plane curves, and just polynomial rings. It should be fairly easy to use:
---------------------------------------------------------------------- | Sage Version 3.4.2.rc0, Release Date: 2009-04-30 | | Type notebook() for the GUI, and license() for information. | ---------------------------------------------------------------------- sage: attach test.sage sage: test_poly_leak(2^17) 271.75390625
This indicates that the memory usage after the loop is 271MB more than before.
Note also that if you run different tests one after the other you can see, e.g. how much of the leakage in elliptic curves is "independent" of the polynomial ring issue:
---------------------------------------------------------------------- | Sage Version 3.4.2.rc0, Release Date: 2009-04-30 | | Type notebook() for the GUI, and license() for information. | ---------------------------------------------------------------------- sage: attach test.sage sage: test_poly_leak(2^17) 271.73046875 sage: test_ec_leak(2^17) 53.10546875
comment:3 in reply to: ↑ 1 ; follow-up: ↓ 4 Changed 11 years ago by
Replying to mabshoff:
Ooops, but this does seem to expose some problems:
Sorry, I did not do any tests, since I thought that weak references Just Work (c), and so the change from a dictionary to a WeakValueDictionary? would be almost trivial.
And something this low level will definitely not go into 3.4.2 at this stage.
Again sorry. Since I thought it is almost trivial, I concluded it could easily be in the next distribution.
If weak references break cython code at a very fundamental level then I see no chance for my approach to work, unless Cython changes.
Won't fix, then?
comment:4 in reply to: ↑ 3 Changed 11 years ago by
- Priority changed from major to blocker
Replying to SimonKing:
Replying to mabshoff:
Ooops, but this does seem to expose some problems:
Sorry, I did not do any tests, since I thought that weak references Just Work (c), and so the change from a dictionary to a WeakValueDictionary? would be almost trivial.
Hehe, I hope you will remember this now :)
And something this low level will definitely not go into 3.4.2 at this stage.
Again sorry. Since I thought it is almost trivial, I concluded it could easily be in the next distribution.
This stems from long experience that every even trivial fix has a non-zero chance of breaking things. Weak references are particularly troublesome in this context. And 3.4.2 was supposed to be out two days ago and now William and I will fix the last couple issues today and push out 3.4.2.final, so no potentially risky patches. I can valgrind this in some 4.0.alphaX (assuming the segfaults go away).
If weak references break cython code at a very fundamental level then I see no chance for my approach to work, unless Cython changes.
Won't fix, then?
No, as mentioned in sage-support RobertWB pointed out some other ticket as guideline to what is wrong.
This patch does not fix the problem the reported in the thread at http://groups.google.com/group/sage-support/t/ef01dae47c835137 reported, but it seems to fix something else or is part of the fix to get #5949 resolved, so lets keep this open for now. It seems to be a valuable patch.
Cheers,
Michael
Cheers,
Michael
comment:5 Changed 11 years ago by
At http://docs.python.org/library/weakref.html they say:
Caution: Because a WeakKeyDictionary? is built on top of a Python dictionary, it must not change size when iterating over it. This can be difficult to ensure for a WeakKeyDictionary? because actions performed by the program during iteration may cause items in the dictionary to vanish “by magic” (as a side effect of garbage collection).
Can this be part of the trouble with my patch?
comment:6 Changed 11 years ago by
- Priority changed from blocker to critical
If we've released for 2 months without fixing this, it doesn't make sense to keep it as a blocker. Note that the lisp interface is in fact 100% completely broken right now.
comment:7 Changed 10 years ago by
- Summary changed from [with patch, needs work] Weak references in Polynomial Ring cache to [with patch, needs review] Weak references in Polynomial Ring cache
The attached patch uses weakrefs for multivariate polynomials but not for univariate polynomials (we still use the same _cache
object to hold both though). It seems the SIGSEGV is due to some Pari issue so the patch seems safe at first sight (famous last words). I will post debug info in a minute.
comment:8 Changed 10 years ago by
Valgrind output for -O0 -ggdb
:
==27448== Invalid write of size 8 ==27448== at 0xA436E60: reset_traps (init.c:510) ==27448== by 0xA438A5B: err_leave (init.c:984) ==27448== by 0x11674DE6: __pyx_f_4sage_4libs_4pari_3gen_12PariInstance_GEN_to_str (gen.c:39989) ==27448== by 0x116048BD: __pyx_pf_4sage_4libs_4pari_3gen_3gen___repr__ (gen.c:3971) ==27448== by 0x44D91E: _PyObject_Str (object.c:424) ==27448== by 0x44D9D2: PyObject_Str (object.c:445) ==27448== by 0x45A0D9: string_new (stringobject.c:4075) ==27448== by 0x4682D2: type_call (typeobject.c:731) ==27448== by 0x41A95C: PyObject_Call (abstract.c:2492) ==27448== by 0x49C3FE: PyEval_EvalFrameEx (ceval.c:3917) ==27448== by 0x4A0908: PyEval_EvalCodeEx (ceval.c:2968) ==27448== by 0x49EFC7: PyEval_EvalFrameEx (ceval.c:3802) ==27448== by 0x4A0908: PyEval_EvalCodeEx (ceval.c:2968) ==27448== by 0x4F74DC: function_call (funcobject.c:524) ==27448== by 0x41A95C: PyObject_Call (abstract.c:2492) ==27448== by 0x4222D3: instancemethod_call (classobject.c:2579) ==27448== by 0x41A95C: PyObject_Call (abstract.c:2492) ==27448== by 0xB7DBC1F: __pyx_pf_4sage_9structure_11sage_object_10SageObject___repr__ (sage_object.c:1387) ==27448== by 0x41A95C: PyObject_Call (abstract.c:2492) ==27448== by 0x4991B5: PyEval_CallObjectWithKeywords (ceval.c:3575) ==27448== by 0x47118D: slot_tp_repr (typeobject.c:5295) ==27448== by 0x44D91E: _PyObject_Str (object.c:424) ==27448== by 0x45F3F5: PyString_Format (stringobject.c:4848) ==27448== by 0x41AFB0: binary_op1 (abstract.c:917) ==27448== by 0x41D97D: PyNumber_Remainder (abstract.c:969) ==27448== Address 0x5c5bdd8 is 0 bytes inside a block of size 424 free'd ==27448== at 0x4C2261F: free (vg_replace_malloc.c:323) ==27448== by 0xA4379AB: pari_close_opts (init.c:715) ==27448== by 0xA437A4E: pari_close (init.c:729) ==27448== by 0x1166D250: __pyx_pf_4sage_4libs_4pari_3gen_12PariInstance__unsafe_deallocate_pari_stack (gen.c:36617) ==27448== by 0x49F050: PyEval_EvalFrameEx (ceval.c:3690) ==27448== by 0x4A0908: PyEval_EvalCodeEx (ceval.c:2968) ==27448== by 0x49EFC7: PyEval_EvalFrameEx (ceval.c:3802) ==27448== by 0x4A0908: PyEval_EvalCodeEx (ceval.c:2968) ==27448== by 0x4A0A21: PyEval_EvalCode (ceval.c:522) ==27448== by 0x4C03AB: PyRun_FileExFlags (pythonrun.c:1335) ==27448== by 0x4C06DA: PyRun_SimpleFileExFlags (pythonrun.c:931) ==27448== by 0x416215: Py_Main (main.c:599) ==27448== by 0x56EA5C5: (below main) (in /lib/libc-2.9.so)
comment:9 Changed 10 years ago by
Just to make sure, this backtrace is not with the patch I just attached but with the original patch.
comment:10 Changed 10 years ago by
Mhh, from the changelog it seems caching was disabled because of a SIGSEGV in matrix2.pyx. I cannot reproduce it though.
comment:11 Changed 10 years ago by
I am having trouble to reproduce the segfault in matrix2.pyx
, cf.
William, do you recall on which platform you saw it?
comment:12 Changed 10 years ago by
- Report Upstream set to N/A
- Summary changed from [with patch, needs review] Weak references in Polynomial Ring cache to Weak references in Polynomial Ring cache
comment:13 Changed 10 years ago by
Hi!
I almost forgot this ticket. But now, it hit me while working at #7580 (I had the impression I got a memory leak there, but in fact the Polynomial Ring cache just contains more and more unused items).
Martin, since your patch is quite different from my original suggestion, I guess that I am allowed to be referee? Or must it be someone else?
Cheers, Simon
comment:14 Changed 10 years ago by
Yes, you are okay to review it. Make sure you push it hard, try to make it crash etc. :)
comment:15 Changed 10 years ago by
This is not a review yet, but some first tests.
There is some progress. Consider the following code snipped (slightly modifying Alex' code):
def test_poly_leak(upper): a = get_memory_usage() c = 0 for p in prime_range(upper): c+=1 R.<x, y, z> = PolynomialRing(GF(p), 3) b = get_memory_usage() return (b - a)/c
So, the average memory allocation for each created polynomial ring is counted.
Result on sage.math:
sage: attach test.sage sage: test_poly_leak(100000) 0.03225588380942452
which I can confirm on my computer with original 4.3.rc0.
With the patch, one has
sage: attach test.sage sage: test_poly_leak(100000) 0.0072749426605504585
I did not yet try to crash the patch intentionally. However, I did some indirect stress tests. Namely, I did some series of random examples of Symmetric Groebner bases (this is about infinite polynomial rings, see #7580). Here, many finite polynomial rings are created. There was no segfault or so, which I take as a good sign.
So long,
Simon
comment:16 Changed 10 years ago by
- Status changed from needs_review to needs_info
- Work issues set to regression for test_ec_leak?
Hi!
Taking the test.sage
file, modifying it by scaling the output by the number of examples, I obtain with sage-4.3.2:
sage: attach test.sage sage: %time test_poly_leak(10^5) CPU times: user 9.38 s, sys: 0.24 s, total: 9.62 s Wall time: 9.63 s 0.032462354696622182 sage: %time test_ec_leak(10^5) CPU times: user 39.26 s, sys: 0.26 s, total: 39.51 s Wall time: 39.52 s 0.021538141944734097 sage: %time test_pc_leak(10^5) CPU times: user 14.63 s, sys: 0.05 s, total: 14.68 s Wall time: 14.70 s 0.0056423158621768136
With the patch (that applies, though with a warning), I obtain:
sage: attach test.sage sage: %time test_poly_leak(10^5) CPU times: user 8.01 s, sys: 0.07 s, total: 8.08 s Wall time: 8.12 s 0.0073502821361551294 sage: %time test_ec_leak(10^5) CPU times: user 49.45 s, sys: 0.34 s, total: 49.79 s Wall time: 49.86 s 0.047167052267987487 sage: %time test_pc_leak(10^5) CPU times: user 14.94 s, sys: 0.08 s, total: 15.02 s Wall time: 15.08 s 0.005620324880108424
Now that's kind of strange. In one of the three tests, there is an improvement in both memory and CPU consumption, in one example more or less nothing changes, and in one example there is a regression in both memory and CPU.
At least, for quite a while I did heavy polynomial computations, involving the temporary creation of many polynomial rings. It never crashed.
So, I would give it a positive review, if there wouldn't be the regression in one of the tests.
Can you explain why this regression occurs?
Best regards,
Simon
comment:17 Changed 10 years ago by
First, I can reproduce your results:
without patch
sage: %time test_poly_leak(10^5) CPU times: user 11.11 s, sys: 0.31 s, total: 11.43 s Wall time: 11.84 s 311.71875 sage: %time test_ec_leak(10^5) CPU times: user 46.12 s, sys: 0.27 s, total: 46.39 s Wall time: 47.27 s 206.26953125 sage: %time test_pc_leak(10^5) CPU times: user 16.95 s, sys: 0.08 s, total: 17.03 s Wall time: 17.64 s 54.1328125
with patch
sage: %time test_poly_leak(10^5) CPU times: user 9.14 s, sys: 0.10 s, total: 9.25 s Wall time: 9.58 s 70.53125 sage: %time test_ec_leak(10^5) CPU times: user 57.96 s, sys: 0.50 s, total: 58.46 s Wall time: 59.63 s 452.3671875 sage: %time test_pc_leak(10^5) CPU times: user 17.03 s, sys: 0.07 s, total: 17.10 s Wall time: 17.53 s 54.23046875
I would assume this is due to the fact that the elliptic curve constructor does its own hashing somewhere (someone more familiar with this area might want to comment on that) which prevents the GC from collecting the unused polynomial rings. Also, since weak references need to keep track of more information I find it plausible that each weak reference has some memory overhead. Since we cannot free the unused polynomial rings this overhead accumulates.
Maybe the elliptic curve constructor should use weak references as well?
comment:18 Changed 9 years ago by
I'd like to revive that ticket.
With sage-4.6.2.alpha0
and the tickets from #8611, #10467 and #10496 (all with positive review), I obtain:
sage: attach test.sage sage: %time test_poly_leak(10^5) CPU times: user 11.63 s, sys: 0.16 s, total: 11.79 s Wall time: 11.85 s 330.4296875 sage: %time test_ec_leak(10^5) CPU times: user 41.47 s, sys: 0.14 s, total: 41.61 s Wall time: 42.11 s 193.3828125 sage: %time test_pc_leak(10^5) CPU times: user 13.24 s, sys: 0.04 s, total: 13.29 s Wall time: 13.29 s 57.25390625
Additionally applying Martin's patch from here, one has
sage: attach test.sage sage: %time test_poly_leak(10^5) CPU times: user 9.09 s, sys: 0.06 s, total: 9.14 s Wall time: 9.26 s 77.1015625 sage: %time test_ec_leak(10^5) CPU times: user 51.72 s, sys: 0.22 s, total: 51.94 s Wall time: 52.49 s 448.65234375 sage: %time test_pc_leak(10^5) CPU times: user 13.64 s, sys: 0.03 s, total: 13.68 s Wall time: 13.85 s 57.796875
So, the situation has not changed: We need to look into the elliptic curves code.
comment:19 Changed 9 years ago by
Now I really wonder whether this ticket is relevant at all.
If I understand correctly, the purpose of this ticket is to use weak references, so that unused polynomial rings can be removed from the cache. But the "test suite" in test.sage
is not affected from the length of the cache:
sage: attach test.sage sage: from sage.rings.polynomial.polynomial_ring_constructor import _cache sage: len(_cache) 16 sage: %time test_poly_leak(10^5) CPU times: user 11.06 s, sys: 0.13 s, total: 11.18 s Wall time: 11.19 s 330.40625 sage: len(_cache) 9608 sage: %time test_ec_leak(10^5) CPU times: user 27.01 s, sys: 0.11 s, total: 27.12 s Wall time: 27.13 s 192.51171875 sage: len(_cache) 9608
The memory consumption depends on applying the patch. But len(_cache)
is the same, with or without the patch.
Also, the original problem
sage: for p in primes(2,1000000): ....: print get_memory_usage() ....: R.<x,y,z> = GF(p)[]
does not seem to be seriously affected by the patch (at least when one has the patches from #8611, #10467 and #10496 applied on top of sage-4.6.2.alpha0
.
Thoughts?
comment:20 Changed 9 years ago by
- Cc jpflori added
comment:21 Changed 8 years ago by
- Cc zimmerma added
comment:22 Changed 8 years ago by
- Status changed from needs_info to needs_review
This is related with a couple of other tickets that aim at using weak references:
- #11521 uses weak references for the cache of homsets.
- #715, which aims at using weak references for the coercion cache.
I think the whole project only makes sense if all three approaches are simultaneously used. Two of them will not be enough.
Currently, I test on top of #11521 and some preliminary patch for #715, whether it is now possible to simply use a WeakValueDictionary
. If it still doesn't then we should revive Martin's patch.
comment:23 Changed 8 years ago by
- Status changed from needs_review to needs_work
comment:24 Changed 8 years ago by
Even using all three techniques is not enough, as I found out with the example from the ticket description.
comment:25 Changed 8 years ago by
- Cc vbraun added
I wonder why the example leaks, though. With the patches from #11521 and a not-yet-published patch for #715, I obtain:
sage: import gc sage: from sage.rings.finite_rings.finite_field_base import is_FiniteField sage: K = GF(151) sage: predicate = lambda x: is_FiniteField(x) and x.order() == 151 sage: del K sage: gc.collect() 174 sage: [bla for bla in gc.get_objects() if predicate(bla)] []
So, prime fields do not seem to leak.
sage: from sage.rings.polynomial.multi_polynomial_ring import is_MPolynomialRing sage: K = GF(151) sage: P = K['x','y','z'] sage: del P sage: gc.collect() 33 sage: predicate = lambda x: is_MPolynomialRing(x) and x.variable_names()==['x','y','z'] and x.base_ring() is K sage: [bla for bla in gc.get_objects() if predicate(bla)] []
So, where does the leak come from??? The example from the ticket description does use polynomial rings over finite prime fields!
comment:26 Changed 8 years ago by
Aha!
The combination of a finite field with a polynomial ring seems to reveal the leak:
sage: K = GF(next_prime(1000)) sage: p = K.order() sage: predicate = lambda x: is_FiniteField(x) and x.order() == p sage: del K sage: gc.collect() 23 sage: [bla for bla in gc.get_objects() if predicate(bla)] [] sage: K = GF(next_prime(1000)) sage: P = K['x','y','z'] sage: del P sage: del K sage: gc.collect() 39 sage: [bla for bla in gc.get_objects() if predicate(bla)] [Finite Field of size 1009] sage: predicate = lambda x: is_MPolynomialRing(x) and x.variable_names()==['x','y','z'] sage: [bla for bla in gc.get_objects() if predicate(bla)] []
So, the polynomial ring is gone, but the base ring remains. And I think this is indeed because of the thing tracked at #12215:
- The polynomial ring belongs to the category of algebras over the base ring (at least by #9138, which I have applied),
- The category is strongly cached (see #12215)
- The category has a reference to its base ring.
So, indeed we absolutely need to have UniqueRepresentation
use weak references.
comment:27 follow-up: ↓ 28 Changed 8 years ago by
I can't really comment on what is going on in your unpublished patch, but I do recommend heapy to track down the memory leaks. For starters, it can show you a statistic of which types occupy most of the memory. Its just an easy_install
away... But we don't have to solve every memory leak in a day, I'm happy to review any progress towards making cache weaker even if its not the final word.
comment:28 in reply to: ↑ 27 Changed 8 years ago by
Replying to vbraun:
I can't really comment on what is going on in your unpublished patch, but I do recommend heapy to track down the memory leaks. ... Its just an
easy_install
away...
It isn't.
(sage subshell) linux-sqwp:sage-main simon$ easy_install heapy Searching for heapy Reading http://pypi.python.org/simple/heapy/ Couldn't find index page for 'heapy' (maybe misspelled?) Scanning index of all packages (this may take a while) Reading http://pypi.python.org/simple/ No local packages or download links found for heapy error: Could not find suitable distribution for Requirement.parse('heapy')
What did I do wrong?
comment:29 Changed 8 years ago by
Aha! Do I need to install guppy for getting heapy?
comment:30 Changed 8 years ago by
Interesting. Heapy shows (again with the example from the ticket description) that most of the memory is filled by strings:
sage: H.heap() Partition of a set of 479076 objects. Total size = 78965680 bytes. Index Count % Size % Cumulative % Kind (class / dict of class) 0 228412 48 38602736 49 38602736 49 str 1 123581 26 10681888 14 49284624 62 tuple 2 1755 0 4241544 5 53526168 68 dict of module 3 4657 1 3835672 5 57361840 73 dict (no owner) 4 29863 6 3583560 5 60945400 77 function 5 29851 6 3582120 5 64527520 82 types.CodeType 6 3071 1 2974952 4 67502472 85 dict of type 7 3071 1 2759672 3 70262144 89 type 8 6651 1 1202264 2 71464408 91 list 9 937 0 922072 1 72386480 92 dict of class <1072 more rows. Type e.g. '_.more' to view.>
What are these strings? Messages of cached exceptions (there is a ticket concerning cached exceptions, but I can't find it right now)? Keys of dictionaries? But then we should also see the corresponding values.
comment:31 Changed 8 years ago by
- Reviewers set to Simon King
- Status changed from needs_work to positive_review
I introduced a weak cache for polynomial rings in two lines of my patch for #715, which now needs review. I therefore suggest that this ticket is marked as a duplicate.
comment:32 follow-up: ↓ 33 Changed 8 years ago by
Simon, there is a duplicate
field, which would be better than positive review
.
Also, maybe you might put this as needs review
, asking someone (maybe you) to check that your patch for #715 indeed solves the problem.
Paul
comment:33 in reply to: ↑ 32 ; follow-up: ↓ 34 Changed 8 years ago by
Replying to zimmerma:
Simon, there is a
duplicate
field, which would be better thanpositive review
.
There is no duplicate field, because choosing the resolution of a ticket is reserved to people with administrator rights. Apparently you have these rights, but I haven't.
In addition, I am very much sure that Jeroen said that this is the correct way to proceed: If one thinks that the ticket is a duplicate then you review it accordingly, putting it as "positive review". Then the RELEASE MANAGER (nobody else!!) closes the ticket by choosing the resolution "duplicate", if he believes that the reasons given in the review make sense.
Also, maybe you might put this as
needs review
, asking someone (maybe you) to check that your patch for #715 indeed solves the problem.
I can of course not review my own patch from #715. I can merely state that the problem of the ticket here is in fact a sub-problem of ticket #715.
comment:34 in reply to: ↑ 33 Changed 8 years ago by
- Description modified (diff)
- Milestone changed from sage-4.8 to sage-duplicate/invalid/wontfix
- Work issues regression for test_ec_leak? deleted
Replying to SimonKing:
I am very much sure that Jeroen said that this is the correct way to proceed: If one thinks that the ticket is a duplicate then you review it accordingly, putting it as "positive review". Then the RELEASE MANAGER (nobody else!!) closes the ticket by choosing the resolution "duplicate", if he believes that the reasons given in the review make sense.
True, but you forget one important step: you should put the milestone to sage-duplicate/invalid/wontfix yourself, so I know the intention is to close this ticket as duplicate and no patch should be merged.
Nobody except for the release manager should close or reopen tickets (with a few exceptions like spam tickets, tickets marked as duplicate by the person who reported the ticket and with no other activity).
And if it's a duplicate, it would be nice to add a pointer in the description to the ticket of which it is a duplicate of.
comment:35 Changed 8 years ago by
- Resolution set to duplicate
- Status changed from positive_review to closed
Introduce Weak Reference to the cache of PolynomialRing?