Skip to content

Fix missing warning in SplittingAlgebra #41016

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 3 commits into
base: develop
Choose a base branch
from
Open

Fix missing warning in SplittingAlgebra #41016

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
cd6456d
fix_splitting_algebra_warning initial
soehms Oct 9, 2025
c3e0cc8
Merge branch 'sagemath:develop' into fix_splitting_algebra_warning
soehms Oct 9, 2025
f8727bd
41016: change keyword default back again
soehms Oct 11, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 5 additions & 2 deletions src/sage/algebras/hecke_algebras/cubic_hecke_algebra.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -102,7 +102,7 @@
sage: s^2
(c0*c1*c2*c3*c4)^2
sage: t = CHA6.an_element() * c4; t
(-w)*c0*c1^-1*c4 + v*c0*c2^-1*c4 + u*c2*c1*c4 + ((-v*w+u)/w)*c4
-w*c0*c1^-1*c4 + v*c0*c2^-1*c4 + u*c2*c1*c4 - ((v*w-u)/w)*c4

REFERENCES:

Expand Down Expand Up @@ -717,7 +717,7 @@ class CubicHeckeAlgebra(CombinatorialFreeModule):
True
sage: CHA4 = algebras.CubicHecke(4) # optional database_cubic_hecke
sage: ele4 = CHA4(ele3); ele4 # optional database_cubic_hecke
c0*c1*c0^-1*c1 + u*c0^-1*c1*c0 + (-v)*c0*c1^-1 + v*c1^-1*c0 + (-u)*c0*c1*c0^-1
c0*c1*c0^-1*c1 + u*c0^-1*c1*c0 - v*c0*c1^-1 + v*c1^-1*c0 - u*c0*c1*c0^-1

Cubic Hecke algebra over the ring of definition using different variable
names::
Expand Down Expand Up @@ -1913,6 +1913,9 @@ def _braid_image_from_filecache(self, braid):
sage: F = CHA3.base_ring().fraction_field()
sage: par = tuple([F(p) for p in CHA3.cubic_equation_parameters()])
sage: CHA3F = algebras.CubicHecke(3, cubic_equation_parameters=par)
doctest:warning
...
UserWarning: Assuming h^3 - u*h^2 + v*h - w to have maximal Galois group!
sage: CHA3F._braid_image_from_filecache(br)
1/w*c0*c1*c0^-1*c1 + v/w*c1^-1*c0 - u/w*c0*c1*c0^-1
sage: section = CHA3.filecache_section().braid_images
Expand Down
37 changes: 29 additions & 8 deletions src/sage/algebras/splitting_algebra.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -220,7 +220,6 @@ def __init__(self, monic_polynomial, names='X',
# ---------------------------------------------------------------
# checking input parameters
# ---------------------------------------------------------------

base_ring = monic_polynomial.base_ring()
if not monic_polynomial.is_monic():
raise ValueError("given polynomial must be monic")
Expand Down Expand Up @@ -270,8 +269,24 @@ def __init__(self, monic_polynomial, names='X',
# assuming this has been checked mathematically before
self._set_modulus_irreducible_ = True
if warning:
warn(f'Assuming {monic_polynomial} to have maximal Galois group!')
warning = False # one warning must be enough
def_pol = monic_polynomial
if isinstance(base_ring, SplittingAlgebra):
# Here we are inside a recursion. Using the splitting field
# over the fractional field of the scalar base ring we may
# find a reason to avoid the warning.
def_pol = base_ring.defining_polynomial()
F = base_ring.scalar_base_ring().fraction_field()
def_pol_f = def_pol.change_ring(F)
try:
E = def_pol_f.splitting_field('Ex')
if E.degree() == def_pol_f.degree().factorial():
# Galois group is maximal
warning = False
except NotImplementedError:
pass
if warning:
warn(f'Assuming {def_pol} to have maximal Galois group!')
warning = False # one warning must be enough

verbose("P %s defined:" % (P))

Expand All @@ -281,7 +296,7 @@ def __init__(self, monic_polynomial, names='X',
# -----------------------------------------------------------
base_ring_step = SplittingAlgebra(monic_polynomial,
tuple(root_names),
iterate=False, warning=False)
iterate=False, warning=warning)
first_root = base_ring_step.gen()

verbose("base_ring_step %s defined:" % (base_ring_step))
Expand All @@ -300,7 +315,7 @@ def __init__(self, monic_polynomial, names='X',
verbose("Invoking recursion with: %s" % (q,))

SplittingAlgebra.__init__(self, q, root_names_reduces,
warning=False)
warning=warning)

splitting_roots = base_ring_step._splitting_roots + self._splitting_roots
coefficients_list = base_ring_step._coefficients_list + self._coefficients_list
Expand Down Expand Up @@ -420,7 +435,7 @@ def _repr_(self) -> str:
sage: from sage.algebras.splitting_algebra import SplittingAlgebra
sage: L.<u, v> = PolynomialRing(ZZ)
sage: t = polygen(L)
sage: Spl.<S, T> = SplittingAlgebra(t^3 - (u^2-v)*t^2 + (v+u)*t - 1)
sage: Spl.<S, T> = SplittingAlgebra(t^3 - (u^2-v)*t^2 + (v+u)*t - 1, warning=False)
sage: Spl._repr_()
'Splitting Algebra of x^3 + (-u^2 + v)*x^2 + (u + v)*x - 1
with roots [S, T, -T - S + u^2 - v]
Expand Down Expand Up @@ -449,6 +464,9 @@ def _first_ngens(self, n) -> tuple:
sage: L.<u, v> = PolynomialRing(ZZ)
sage: t = polygen(L)
sage: S.<X, Y> = SplittingAlgebra(t^3 - (u^2-v)*t^2 + (v+u)*t - 1) # indirect doctest
doctest:warning
...
UserWarning: Assuming x^3 + (-u^2 + v)*x^2 + (u + v)*x - 1 to have maximal Galois group!
sage: X.parent()
Splitting Algebra of x^3 + (-u^2 + v)*x^2 + (u + v)*x - 1
with roots [X, Y, -Y - X + u^2 - v]
Expand All @@ -470,7 +488,7 @@ def _element_constructor_(self, x):

sage: from sage.algebras.splitting_algebra import SplittingAlgebra
sage: L.<u, v, w> = LaurentPolynomialRing(ZZ); x = polygen(L)
sage: S.<X, Y> = SplittingAlgebra(x^3 - u*x^2 + v*x - w)
sage: S.<X, Y> = SplittingAlgebra(x^3 - u*x^2 + v*x - w, warning=False)
sage: S(u + v)
u + v
sage: S(X*Y + X)
Expand All @@ -495,6 +513,9 @@ def hom(self, im_gens, codomain=None, check=True, base_map=None):
sage: from sage.algebras.splitting_algebra import SplittingAlgebra
sage: L.<u, v, w> = LaurentPolynomialRing(ZZ); x = polygen(L)
sage: S = SplittingAlgebra(x^3 - u*x^2 + v*x - w, ('X', 'Y'))
doctest:warning
...
UserWarning: Assuming x^3 - u*x^2 + v*x - w to have maximal Galois group!
sage: P.<x, y, z> = PolynomialRing(ZZ)
sage: F = FractionField(P)
sage: im_gens = [F(g) for g in [y, x, x + y + z, x*y+x*z+y*z, x*y*z]]
Expand Down Expand Up @@ -702,7 +723,7 @@ def solve_with_extension(monic_polynomial, root_names=None, var='x',
sage: _[0][0].parent()
Universal Cyclotomic Field
"""
def create_roots(monic_polynomial, warning=True):
def create_roots(monic_polynomial, warning=warning):
r"""
This internal function creates all roots of a polynomial in an
appropriate extension ring assuming that none of the roots is
Expand Down
Loading