This example is definitely leaving loads of stuff on the python heap, so if
there is a leak onto the cython heap then it is not the only one. My guess
would be an interaction with the coercion system or UniqueRepresentation,
which both keeps global weak references to objects. If the key information
ends up containing objects that hold a reference to the values in a weakly
valued dictionary, the garbage collector can not remove the cycle. These
things are hellish to debug. The code below does find the relevant objects
on the heap, though, so you can plot the backwards reference graphs of some
of these objects to see what kinds of links are involved. We have resolved
some of these bugs in the past.
```
import gc
from collections import Counter
gc.collect()
pre={id(a) for a in gc.get_objects()}
for A2 in range(1, 1000):
Kn=NumberField(x^2+A2,'w')
m=Kn.class_group().order()
del Kn, m
gc.collect()
gc.collect()
T=Counter(str(type(a)) for a in gc.get_objects() if id(a) not in pre)
T
```
Notes for the code above:
- if you run it twice you get a nearly empty list from T, which is
consistent with UniqueRepresentation objects remaining (they would not be
recreated if they already exist).
- this is confirmed by rerunning the loop but now with another name than
'w' for Kn. Now new objects do get created!
On Wednesday 4 September 2024 at 06:09:37 UTC-7 Georgi Guninski wrote:
> Probably this shares the same bug as [1]
>
> Calling `NumberField().class_group().order()` in a loop of size N:
> #10^3 leaks: 40.03 MB 40026112 pari= [7950, 1451665]
> #10^4 leaks: 338.49 MB 338493440 pari= [83505, 19297360]
>
> The leak appears to be in the pari heap.
>
> Code .sage:
> ====
> #Author Georgi Guninski Wed Sep 4 12:58:18 PM UTC 2024
> #10^3 leaks: 40.03 MB 40026112 pari= [7950, 1451665]
> #10^4 leaks: 338.49 MB 338493440 pari= [83505, 19297360]
>
> import psutil,gc,sys
>
> from sage.all import EllipticCurve
> ps = psutil.Process()
> num=10**3 #10**5 // 2
> x=var('x')
> def leaknf5(N=10**3):
> gc.collect()
> base = ps.memory_info().rss
> for A2 in range(1, N):
> Kn=NumberField(x^2+A2,'w')
> m=Kn.class_group().order()
> gc.collect()
> mem = ps.memory_info().rss - base
> print(f"{mem/1e6 :.2f} MB ",mem," pari=",pari.getheap())
>
> leaknf5(10**4)
> ====
>
> [1]: https://groups.google.com/g/sage-devel/c/fWBls6YbXmw
> Memory leak in |EllipticCurve([n,0]).root_number()| and problem in
> algebraic geometry
>
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