Memory leak when doing ANF of boolean functions?

asked 2016-11-17 09:50:56 +0100

sageuser1
97 ●5 ●10

updated 2016-11-17 14:45:05 +0100

I am using SageMath version 7.2 (EDIT: I confirm the same behavior under Sage version 7.4)

sage: B = random_boolean_function(3)
sage: get_memory_usage()
732.5078125
sage: B.algebraic_normal_form()
x0*x1*x2 + x0*x1 + x0 + x2
sage: get_memory_usage()
743.53125
sage: B.algebraic_normal_form()
x0*x1*x2 + x0*x1 + x0 + x2
sage: get_memory_usage()
749.04296875
sage: B.algebraic_normal_form()
x0*x1*x2 + x0*x1 + x0 + x2
sage: get_memory_usage()
754.6875
sage: B.algebraic_normal_form()
x0*x1*x2 + x0*x1 + x0 + x2
sage: get_memory_usage()
760.19921875

After each ANF call the memory used is rising. Is this a memory leak?

Comments

I confirm the same behavior under Sage version 7.4

sageuser1 ( 2016-11-17 14:44:25 +0100 )edit

Thanks for reporting !

tmonteil ( 2016-11-18 11:57:07 +0100 )edit

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answered 2016-11-17 19:34:57 +0100

nbruin
4153 ●3 ●45 ●91

updated 2016-11-18 00:23:56 +0100

Yes, this is a memory leak. if you read the code you see that algebraic_normal_form creates a BooleanPolynomialRing every time. These stack up. A little work with objgraph.show_backref shows that there is a (global?) WeakValueDictionary linking to these objects, preventing them from being garbage collected.

There is likely some coercion map being cached.

It's now bug https://trac.sagemath.org/ticket/21892

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Comments

Thank you for the update!

sageuser1 ( 2016-11-18 07:39:23 +0100 )edit

Thanks for the ticket !

tmonteil ( 2016-11-18 11:57:19 +0100 )edit

Such parents should have unique representation, right ? So why are they not pointing to the same object ?

sage: B = random_boolean_function(3)
sage: a = B.algebraic_normal_form().parent()
sage: b = B.algebraic_normal_form().parent()
sage: a
Boolean PolynomialRing in x0, x1, x2
sage: b
Boolean PolynomialRing in x0, x1, x2
sage: a is b
False

tmonteil ( 2016-11-18 11:59:39 +0100 )edit

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Memory leak when doing ANF of boolean functions?

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