Valuation on power series and Laurent series #39517

xcaruso · 2025-02-13T17:33:02Z

We implement the method valuation on the rings of power series and Laurent series.

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The title is concise and informative.
The description explains in detail what this PR is about.
I have linked a relevant issue or discussion.
I have created tests covering the changes.
I have updated the documentation and checked the documentation preview.

xcaruso · 2025-02-13T17:33:37Z

I still have a problem with categories that I do not understand. Please tell me if you have some insight.

saraedum · 2025-02-13T17:54:38Z

src/sage/rings/series_valuation.py

+
+from sage.rings.valuation.valuation import DiscreteValuation
+
+class SeriesValuation(DiscreteValuation):


Have you considered making this a UniqueRepresentation? Then you can throw out _eq_ and __reduce__ from your implementation.

Yes, I tried it (not so hard). But got an error that I did not really understand (something with metaclasses).

Ah, that's annoying. Then you need to add a silly little factory.

Let me know if you need any support here (I can add it if you want me to.)

I don't think you need a factory, but you probably need the right metaclass, which I think is from sage.misc.inherit_comparison import InheritComparisonClasscallMetaclass.

mantepse · 2025-02-13T17:54:55Z

could you add this simultaneously to the lazy power / Laurent series?

or should this be actually a method in a category?

saraedum · 2025-02-13T17:55:42Z

src/sage/rings/laurent_series_ring.py

+        valuation_space = DiscretePseudoValuationSpace(self)
+        return SeriesValuation(valuation_space)


You want to do valuation_space.__make_element_class__(SeriesValuation)(valuation_space) to get the category right.

src/sage/rings/series_valuation.py

xcaruso · 2025-02-13T17:58:26Z

could you add this simultaneously to the lazy power / Laurent series?

Sure, I will do it.

saraedum · 2025-02-13T18:10:09Z

src/sage/rings/series_valuation.py

+            sage: v  # indirect doctest
+            t-adic valuation
+        """
+        return "%s-adic valuation" % self.domain().uniformizer()


Suggested change

return "%s-adic valuation" % self.domain().uniformizer()

return "%s-adic valuation" % self.uniformizer()

I think it would be good to implement uniformizer() on the level of valuation.

Actually, once the "category" test above passes, more tests coming from the category of discrete valuations are going to fail, namely that you are missing a bunch of methods: uniformizer, reduce, lift, residue_field.

github-actions · 2025-02-13T18:16:02Z

Documentation preview for this PR (built with commit 1fcf1e6; changes) is ready! 🎉
This preview will update shortly after each push to this PR.

xcaruso · 2025-02-13T20:49:26Z

Thanks for your help. I think that everything is working correctly now.

saraedum · 2025-02-14T08:47:27Z

src/sage/rings/series_valuation.py

+
+    def create_object(self, version, key, **extra_args):
+        r"""
+        Create a unique key identifying the valuation of ``R``.


Actually this creates the object. That's the docstring for the other method I guess.

saraedum · 2025-02-14T08:48:10Z

src/sage/rings/series_valuation.py

+SeriesValuation = SeriesValuationFactory("sage.rings.series_valuation.SeriesValuation")
+
+
+class SeriesValuation_base(DiscreteValuation):


Maybe _generic since there's nobody inheriting from this. Base sounds like abstract base to me (just a suggestion. Keep it if you want.)

saraedum · 2025-02-14T08:51:37Z

doctests fail with:

File "src/sage/rings/series_valuation.py", line 30, in sage.rings.series_valuation.SeriesValuationFactory
Failed example:
    v = R.valuation()
Exception raised:
    Traceback (most recent call last):
      File "/home/runner/miniconda3/envs/sage-dev/lib/python3.11/site-packages/sage/doctest/forker.py", line 728, in _run
        self.compile_and_execute(example, compiler, test.globs)
      File "/home/runner/miniconda3/envs/sage-dev/lib/python3.11/site-packages/sage/doctest/forker.py", line 1152, in compile_and_execute
        exec(compiled, globs)
      File "<doctest sage.rings.series_valuation.SeriesValuationFactory[1]>", line 1, in <module>
        v = R.valuation()
            ^^^^^^^^^^^^^
      File "/home/runner/miniconda3/envs/sage-dev/lib/python3.11/site-packages/sage/rings/power_series_ring.py", line 672, in valuation
        from sage.rings.series_valuation import SeriesValuation
    ModuleNotFoundError: No module named 'sage.rings.series_valuation'

fchapoton · 2025-02-21T15:10:16Z

je me suis permis de corriger les problemes du "linter".

Attention à bien faire "git pull" avant de travailler a nouveau sur la branche.

…aluations introduced

saraedum · 2025-03-01T11:59:07Z

@xcaruso there are a bunch of things that don't seem to work yet:

sage: R.<t> = QQ[[]]
sage: v = R.valuation()
sage: TestSuite(v).run()
Failure in _test_element_with_valuation:
Traceback (most recent call last):
  File "/home/jule/proj/sage/sage/src/sage/misc/sage_unittest.py", line 298, in run
    test_method(tester=tester)
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 1319, in _test_element_with_valuation
    for s in tester.some_elements(self.value_semigroup().some_elements()):
                                  ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 447, in value_semigroup
    raise NotImplementedError("cannot determine value semigroup of %r" % (self,))
NotImplementedError: cannot determine value semigroup of t-adic valuation
------------------------------------------------------------
Failure in _test_shift:
Traceback (most recent call last):
  File "element.pyx", line 1863, in sage.structure.element.Element._floordiv_
  File "element.pyx", line 495, in sage.structure.element.Element.__getattr__
  File "element.pyx", line 508, in sage.structure.element.Element.getattr_from_category
  File "getattr.pyx", line 363, in sage.cpython.getattr.getattr_from_other_class
AttributeError: 'RationalField_with_category' object has no attribute '_SageObject__custom_name'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/jule/proj/sage/sage/src/sage/misc/sage_unittest.py", line 298, in run
    test_method(tester=tester)
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 1133, in _test_shift
    y = self.shift(x, s)
        ^^^^^^^^^^^^^^^^
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 906, in shift
    x //= self.uniformizer()
  File "element.pyx", line 1830, in sage.structure.element.Element.__floordiv__
  File "element.pyx", line 1865, in sage.structure.element.Element._floordiv_
TypeError: unsupported operand parent(s) for //: 'Power Series Ring in t over Rational Field' and 'Power Series Ring in t over Rational Field'
------------------------------------------------------------
Failure in _test_value_semigroup:
Traceback (most recent call last):
  File "/home/jule/proj/sage/sage/src/sage/misc/sage_unittest.py", line 298, in run
    test_method(tester=tester)
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 1301, in _test_value_semigroup
    for s in tester.some_elements(self.value_semigroup().some_elements()):
                                  ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 447, in value_semigroup
    raise NotImplementedError("cannot determine value semigroup of %r" % (self,))
NotImplementedError: cannot determine value semigroup of t-adic valuation
------------------------------------------------------------
The following tests failed: _test_element_with_valuation, _test_shift, _test_value_semigroup

Also in the lazy case:

sage: R.<t> = LazyPowerSeriesRing(QQ)
sage: TestSuite(R.valuation()).run()
Failure in _test_element_with_valuation:
Traceback (most recent call last):
  File "/home/jule/proj/sage/sage/src/sage/misc/sage_unittest.py", line 298, in run
    test_method(tester=tester)
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 1319, in _test_element_with_valuation
    for s in tester.some_elements(self.value_semigroup().some_elements()):
                                  ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 447, in value_semigroup
    raise NotImplementedError("cannot determine value semigroup of %r" % (self,))
NotImplementedError: cannot determine value semigroup of t-adic valuation
------------------------------------------------------------
Failure in _test_shift:
Traceback (most recent call last):
  File "/home/jule/proj/sage/sage/src/sage/misc/sage_unittest.py", line 298, in run
    test_method(tester=tester)
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 1133, in _test_shift
    y = self.shift(x, s)
        ^^^^^^^^^^^^^^^^
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 899, in shift
    if ~self.uniformizer() in self.domain():
       ^^^^^^^^^^^^^^^^^^^
  File "/home/jule/proj/sage/sage/src/sage/rings/lazy_series.py", line 3296, in __invert__
    raise ZeroDivisionError("cannot divide by a series of positive valuation")
ZeroDivisionError: cannot divide by a series of positive valuation
------------------------------------------------------------
Failure in _test_value_semigroup:
Traceback (most recent call last):
  File "/home/jule/proj/sage/sage/src/sage/misc/sage_unittest.py", line 298, in run
    test_method(tester=tester)
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 1301, in _test_value_semigroup
    for s in tester.some_elements(self.value_semigroup().some_elements()):
                                  ^^^^^^^^^^^^^^^^^^^^^^
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 447, in value_semigroup
    raise NotImplementedError("cannot determine value semigroup of %r" % (self,))
NotImplementedError: cannot determine value semigroup of t-adic valuation
------------------------------------------------------------
The following tests failed: _test_element_with_valuation, _test_shift, _test_value_semigroup

and some problems in the lazy laurent case:

sage: TestSuite(R.fraction_field().valuation()).run()
Failure in _test_inverse:
Traceback (most recent call last):
  File "/home/jule/proj/sage/sage/src/sage/misc/sage_unittest.py", line 298, in run
    test_method(tester=tester)
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 1589, in _test_inverse
    tester.assertGreaterEqual(self(x * y - 1), prec)
  File "/home/jule/proj/umamba/envs/sage-dev/lib/python3.11/unittest/case.py", line 1277, in assertGreaterEqual
    self.fail(self._formatMessage(msg, standardMsg))
  File "/home/jule/proj/umamba/envs/sage-dev/lib/python3.11/unittest/case.py", line 703, in fail
    raise self.failureException(msg)
AssertionError: 0 not greater than or equal to 1
------------------------------------------------------------
Failure in _test_shift:
Traceback (most recent call last):
  File "/home/jule/proj/sage/sage/src/sage/misc/sage_unittest.py", line 298, in run
    test_method(tester=tester)
  File "/home/jule/proj/sage/sage/src/sage/rings/valuation/valuation_space.py", line 1140, in _test_shift
    tester.assertEqual(x, self.shift(y, -s))
  File "/home/jule/proj/umamba/envs/sage-dev/lib/python3.11/unittest/case.py", line 873, in assertEqual
    assertion_func(first, second, msg=msg)
  File "/home/jule/proj/umamba/envs/sage-dev/lib/python3.11/unittest/case.py", line 866, in _baseAssertEqual
    raise self.failureException(msg)
AssertionError: -2*t^-3 - 2*t^-2 + 4*t^-1 + 11 - t - 34*t^2 - 31*t^3 + O(t^4) != -2*t^-3 - 2*t^-2 + 4*t^-1 + 11 - t - 34*t^2 - 31*t^3 + O(t^4)
------------------------------------------------------------
The following tests failed: _test_inverse, _test_shift

saraedum · 2025-03-01T12:06:54Z

The semigroup has been fixed, the other things still fail.

valuation of power series and Laurent series

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xcaruso added the sd128 tickets of Sage Days 128 Le Teich label Feb 13, 2025

xcaruso requested a review from saraedum February 13, 2025 17:33

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src/sage/rings/series_valuation.py Outdated Show resolved Hide resolved

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saraedum reviewed Feb 13, 2025

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implement a factory and required methods

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implementation on lazy Laurent series rings

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fix various things

92a950d

fchapoton added the c: commutative algebra label Feb 21, 2025

fix the linter in series_valuation.py

f31283a

saraedum added 2 commits February 28, 2025 17:11

Merge branch 'develop' into valuation_laurent_series

03a7090

Clean up valuation doc strings and run test suites for all types of v…

aaaf9e3

…aluations introduced

saraedum added s: needs work and removed s: needs review labels Mar 1, 2025

Add value_semigroup for series valuations

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Valuation on power series and Laurent series #39517

Valuation on power series and Laurent series #39517

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saraedum commented Mar 1, 2025


		from sage.rings.valuation.valuation import DiscreteValuation

		class SeriesValuation(DiscreteValuation):

		valuation_space = DiscretePseudoValuationSpace(self)
		return SeriesValuation(valuation_space)

	return "%s-adic valuation" % self.domain().uniformizer()
	return "%s-adic valuation" % self.uniformizer()

		SeriesValuation = SeriesValuationFactory("sage.rings.series_valuation.SeriesValuation")


		class SeriesValuation_base(DiscreteValuation):

Valuation on power series and Laurent series #39517

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Valuation on power series and Laurent series #39517

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xcaruso commented Feb 13, 2025

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