conda-forge-macos: RuntimeError from qqbar cmp_elements_with_same_minpoly

[mkoeppe]

From ​https://groups.google.com/g/sage-release/c/6WjKQt_e_B8/m/dpx1qILOCwAJ (for 9.3.rc2):

macos (conda-forge-macos, minimal, default, macos-10.15): (same on minimal-macos-11.0, and standard-{macos-10.15,macos-11.0)) docbuild error (​https://github.com/sagemath/sage/runs/2282411222?check_suite_focus=true)

[categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/rings/qqbar.py", line 5236, in _richcmp_
[categorie]     return bool(self) == (op == op_NE)
[categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/rings/qqbar.py", line 3900, in __bool__
[categorie]     c = cmp_elements_with_same_minpoly(left, right, left.minpoly())
[categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/rings/qqbar.py", line 2720, in cmp_elements_with_same_minpoly
[categorie]     raise RuntimeError('a = {}\nb = {}\np = {}'.format(a, b, p))
[categorie] RuntimeError: a = 2.917983368234029?e15
[categorie] b = 2.917983368234029?e15
[categorie] p = x^6 - 5835966736468056*x^5 + 2658455991569831813923974927379870544*x^4 + 2658455991569831814199401327502424704*x^3 + 2658455991569831809001982851260652032*x^2 + 253512790118400*x + 4096

Most probably the origin is the sphinx plot directive at sage/categories/finite_coxeter_groups.py:731-736

            .. PLOT::
                :width: 300 px

                W = CoxeterGroup(['I',7])
                p = W.permutahedron()
                sphinx_plot(p)

In other words, a call to

sage: W = CoxeterGroup(['I',7])
sage: p = W.permutahedron()
sage: G = p.plot()

should trigger the same error.

[vdelecroix]

I am glad I put this RuntimeError so that we have a bit of information. In the log we somehow believe that a == b. However the polynomial p does not seem to have a or b as roots

sage: x = polygen(QQ)
sage: p = x^6 - 5835966736468056*x^5 + 2658455991569831813923974927379870544*x^4 + 2658455991569831814199401327502424704*x^3 + 2658455991569831809001982851260652032*x^2 + 253512790118400*x + 4096
sage: p.roots(QQbar, multiplicities=False)                                                                                                                                                     
[-0.500000000000000? - 0.866025403784439?*I,
 -0.500000000000000? + 0.866025403784439?*I,
 -4.768045642248970?e-23 - 3.925231146706542?e-17*I,
 -4.768045642248970?e-23 + 3.925231146706542?e-17*I,
 2.917983368234029?e15 - 1.630474617080222?e18*I,
 2.917983368234029?e15 + 1.630474617080222?e18*I]

Here a and b seem to be the real parts of the last pairs of roots above. In other words, the minimal polynomial p is wrong!

[vdelecroix]

Couldn't we have a more complete trace? The information is not enough to reproduce anything.

[vdelecroix]

Would it be possible to run the docbuild in the same environment with the following patch applied

src/sage/rings/qqbar.py

@@ -2695 +2695 @@
         sage: cmp_elements_with_same_minpoly(-a, b, p)
         0
     """
+    # DEBUGGING
+    with open('/tmp/qqbar.log', 'a') as output:
+        import traceback
+        output.write('-'*80)
+        output.write('\n')
+        output.write("cmp_elements_with_same_minpoly(a={}, b={}, p={})\n".format(a, b, p))
+        traceback.print_stack(limit=None, file=output)
+
     ar = a._value.real()
     br = b._value.real()
     if not ar.overlaps(br):

With the patch, any call to cmp_elements_with_same_minpoly is stored into the log file /tmp/qqbar.log. (I will post mine when it finishes).

[vdelecroix]

In my log I notice a very similar trace with data

--------------------------------------------------------------------------------
cmp_elements_with_same_minpoly(a=2.917983368234029?e15, b=2.917983368234029?e15, p=x^3 - 2917983368234028*x^2 - 1980568672800*x - 64)

However p is different (degree 3 here instead of 6 in the ticket description). The trace shows that it comes from the permutahedron as well

  File "/opt/sage/local/lib/python3.9/site-packages/sage/categories/finite_coxeter_groups.py", line 752, in permutahedron
    return Polyhedron(vertices=vertices, base_ring=base_ring)
  File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/constructor.py", line 661, in Polyhedron
    return parent(Vrep, Hrep, convert=convert, verbose=verbose)
  File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/parent.py", line 597, in _element_constructor_
    return self.element_class(self, Vrep, Hrep, **kwds)
  File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/base.py", line 248, in __init__
    self._init_from_Vrepresentation(vertices, rays, lines, **kwds)
  File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/backend_field.py", line 193, in _init_from_Vrepresentation
    H = Vrep2Hrep(self.base_ring(), self.ambient_dim(), vertices, rays, lines)
  File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/double_description_inhomogeneous.py", line 457, in __init__
    DD = Algorithm(A).run()
  File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/double_description.py", line 763, in run
    DD.add_inequality(a)
  File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/double_description.py", line 714, in add_inequality
    if not self.are_adjacent(rp, rn):
  File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/double_description.py", line 446, in are_adjacent
    Z = self.zero_set(r1).intersection(self.zero_set(r2))
  File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/double_description.py", line 375, in zero_set
    t.update(self.A[i] for i in range(n,len(self.A)) if self.A[i].inner_product(ray) == self.zero)
  File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/double_description.py", line 375, in <genexpr>
    t.update(self.A[i] for i in range(n,len(self.A)) if self.A[i].inner_product(ray) == self.zero)
  File "/opt/sage/local/lib/python3.9/site-packages/sage/rings/qqbar.py", line 5244, in _richcmp_
    return bool(self) == (op == op_NE)
  File "/opt/sage/local/lib/python3.9/site-packages/sage/rings/qqbar.py", line 3908, in __bool__
    c = cmp_elements_with_same_minpoly(left, right, left.minpoly())
  File "/opt/sage/local/lib/python3.9/site-packages/sage/rings/qqbar.py", line 2704, in cmp_elements_with_same_minpoly
    traceback.print_stack(limit=None, file=output)

[mkoeppe]

Complete trace (from the GH URL in the ticket description) -> "view raw logs"

2021-04-07T18:09:49.3130260Z [categorie]  from /Users/runner/work/sage/sage/src/doc/en/reference/categories/sage/categories/finite_coxeter_groups.rst:
2021-04-07T18:09:49.3131130Z [categorie] Traceback (most recent call last):
2021-04-07T18:09:49.3132960Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/matplotlib/sphinxext/plot_directive.py", line 472, in run_code
2021-04-07T18:09:49.3134300Z [categorie]     exec(code, ns)
2021-04-07T18:09:49.3134820Z [categorie]   File "<string>", line 2, in <module>
2021-04-07T18:09:49.3136980Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/categories/finite_coxeter_groups.py", line 752, in permutahedron
2021-04-07T18:09:49.3138350Z [categorie]     return Polyhedron(vertices=vertices, base_ring=base_ring)
2021-04-07T18:09:49.3140200Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/geometry/polyhedron/constructor.py", line 661, in Polyhedron
2021-04-07T18:09:49.3141610Z [categorie]     return parent(Vrep, Hrep, convert=convert, verbose=verbose)
2021-04-07T18:09:49.3142870Z [categorie]   File "sage/structure/parent.pyx", line 900, in sage.structure.parent.Parent.__call__ (build/cythonized/sage/structure/parent.c:9362)
2021-04-07T18:09:49.3144230Z [categorie]     return mor._call_with_args(x, args, kwds)
2021-04-07T18:09:49.3145430Z [categorie]   File "sage/structure/coerce_maps.pyx", line 180, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_with_args (build/cythonized/sage/structure/coerce_maps.c:5153)
2021-04-07T18:09:49.3147260Z [categorie]     raise
2021-04-07T18:09:49.3148440Z [categorie]   File "sage/structure/coerce_maps.pyx", line 175, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_with_args (build/cythonized/sage/structure/coerce_maps.c:5041)
2021-04-07T18:09:49.3149620Z [categorie]     return C._element_constructor(x, *args, **kwds)
2021-04-07T18:09:49.3151900Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/geometry/polyhedron/parent.py", line 597, in _element_constructor_
2021-04-07T18:09:49.3153320Z [categorie]     return self.element_class(self, Vrep, Hrep, **kwds)
2021-04-07T18:09:49.3155080Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/geometry/polyhedron/base.py", line 248, in __init__
2021-04-07T18:09:49.3156330Z [categorie]     self._init_from_Vrepresentation(vertices, rays, lines, **kwds)
2021-04-07T18:09:49.3158230Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/geometry/polyhedron/backend_field.py", line 193, in _init_from_Vrepresentation
2021-04-07T18:09:49.3159680Z [categorie]     H = Vrep2Hrep(self.base_ring(), self.ambient_dim(), vertices, rays, lines)
2021-04-07T18:09:49.3161580Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/geometry/polyhedron/double_description_inhomogeneous.py", line 457, in __init__
2021-04-07T18:09:49.3162830Z [categorie]     DD = Algorithm(A).run()
2021-04-07T18:09:49.3164440Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/geometry/polyhedron/double_description.py", line 763, in run
2021-04-07T18:09:49.3165620Z [categorie]     DD.add_inequality(a)
2021-04-07T18:09:49.3167270Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/geometry/polyhedron/double_description.py", line 714, in add_inequality
2021-04-07T18:09:49.3168790Z [categorie]     if not self.are_adjacent(rp, rn):
2021-04-07T18:09:49.3171070Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/geometry/polyhedron/double_description.py", line 446, in are_adjacent
2021-04-07T18:09:49.3172770Z [categorie]     Z = self.zero_set(r1).intersection(self.zero_set(r2))
2021-04-07T18:09:49.3174720Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/geometry/polyhedron/double_description.py", line 375, in zero_set
2021-04-07T18:09:49.3176130Z [categorie]     t.update(self.A[i] for i in range(n,len(self.A)) if self.A[i].inner_product(ray) == self.zero)
2021-04-07T18:09:49.3178280Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/geometry/polyhedron/double_description.py", line 375, in <genexpr>
2021-04-07T18:09:49.3179760Z [categorie]     t.update(self.A[i] for i in range(n,len(self.A)) if self.A[i].inner_product(ray) == self.zero)
2021-04-07T18:09:49.3180990Z [categorie]   File "sage/structure/element.pyx", line 1109, in sage.structure.element.Element.__richcmp__ (build/cythonized/sage/structure/element.c:10345)
2021-04-07T18:09:49.3182110Z [categorie]     return (<Element>self)._richcmp_(other, op)
2021-04-07T18:09:49.3183200Z [categorie]   File "sage/structure/element.pyx", line 1113, in sage.structure.element.Element._richcmp_ (build/cythonized/sage/structure/element.c:10451)
2021-04-07T18:09:49.3184300Z [categorie]     cpdef _richcmp_(left, right, int op):
2021-04-07T18:09:49.3185880Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/rings/qqbar.py", line 5236, in _richcmp_
2021-04-07T18:09:49.3187000Z [categorie]     return bool(self) == (op == op_NE)
2021-04-07T18:09:49.3188790Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/rings/qqbar.py", line 3900, in __bool__
2021-04-07T18:09:49.3190260Z [categorie]     c = cmp_elements_with_same_minpoly(left, right, left.minpoly())
2021-04-07T18:09:49.3192070Z [categorie]   File "/Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/lib/python3.8/site-packages/sage/rings/qqbar.py", line 2720, in cmp_elements_with_same_minpoly
2021-04-07T18:09:49.3193650Z [categorie]     raise RuntimeError('a = {}\nb = {}\np = {}'.format(a, b, p))
2021-04-07T18:09:49.3194290Z [categorie] RuntimeError: a = 2.917983368234029?e15
2021-04-07T18:09:49.3195370Z [categorie] b = 2.917983368234029?e15
2021-04-07T18:09:49.3196950Z [categorie] p = x^6 - 5835966736468056*x^5 + 2658455991569831813923974927379870544*x^4 + 2658455991569831814199401327502424704*x^3 + 2658455991569831809001982851260652032*x^2 + 253512790118400*x + 4096
2021-04-07T18:09:49.3198510Z [manifolds] The inventory files are in .tox/local-conda-forge-macos-minimal/local/share/doc/sage/inventory/en/reference/manifolds.
2021-04-07T18:09:49.3200830Z Build finished. The built documents can be found in /Users/runner/work/sage/sage/.tox/local-conda-forge-macos-minimal/local/share/doc/sage/inventory/en/reference/manifolds

[vdelecroix]

Thanks Matthias. Coincide with what I got. I can not imagine how the computation of the minimal polynomial got wrong specifically on macos....

[mkoeppe]

Is your test on macOS too? with conda-forge?

[vdelecroix]

No no no. I am using an Intel PC under archlinux. If you have access to macOS it would be nice to check whether the 3 lines from the ticket description also trigger the error.

[mkoeppe]

Thanks for the clarification. The failure was specific to a build using conda-forge. I just tried the three lines locally on macos-10.15 with homebrew; there is no error. I'll try now on a build with conda-forge

[mkoeppe]

Reproduced this error locally using tox -e local-conda-forge-macos-standard. The three lines give:

$ ./sage
┌────────────────────────────────────────────────────────────────────┐
│ SageMath version 9.3.rc2, Release Date: 2021-04-06                 │
│ Using Python 3.8.2. Type "help()" for help.                        │
└────────────────────────────────────────────────────────────────────┘
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
┃ Warning: this is a prerelease version, and it may be unstable.     ┃
┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
sage: sage: W = CoxeterGroup(['I',7]) 
....: sage: p = W.permutahedron() 
....: sage: G = p.plot()                                                                                                                                                                                                                     
...
~/local/lib/python3.8/site-packages/sage/rings/qqbar.py in cmp_elements_with_same_minpoly(a, b, p)
   2718              and r._value.imag().overlaps(imag)]
   2719     if not oroots:
-> 2720         raise RuntimeError('a = {}\nb = {}\np = {}'.format(a, b, p))
   2721     if len(oroots) == 1:
   2722         # There is a single root matching both descriptors

RuntimeError: a = 2.917983368234029?e15
b = 2.917983368234029?e15
p = x^6 - 5835966736468056*x^5 + 2658455991569831813923974927379870544*x^4 + 2658455991569831814199401327502424704*x^3 + 2658455991569831809001982851260652032*x^2 + 253512790118400*x + 4096

[mkoeppe]

config.log (tox -e local-conda-forge-macos-standard)

[vdelecroix]

Great that you can test it! Rough guess: might come from algebra library (flint? singular?). I will try to isolate even more the example.

[mmezzarobba]

(forget this comment, I misunderstood the issue)

[mkoeppe]

Moving to 9.4, as 9.3 has been released.

[vdelecroix]

I do have the same problem now on 9.4.beta3 with a sage built from source inside a conda environment on a PC with archlinux

[dochtml] [categorie] /opt/sage/local/lib/python3.9/site-packages/sage/categories/finite_coxeter_groups.py:docstring of sage.categories.finite_coxeter_groups.FiniteCoxeterGroups.ParentMethods.permutahedron:50: WARNING: Exception occurred in plotting finite_coxeter_groups-1
[dochtml] [categorie]  from /opt/sage/src/doc/en/reference/categories/sage/categories/finite_coxeter_groups.rst:
[dochtml] [categorie] Traceback (most recent call last):
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/matplotlib/sphinxext/plot_directive.py", line 472, in run_code
[dochtml] [categorie]     exec(code, ns)
[dochtml] [categorie]   File "<string>", line 2, in <module>
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/categories/finite_coxeter_groups.py", line 752, in permutahedron
[dochtml] [categorie]     return Polyhedron(vertices=vertices, base_ring=base_ring)
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/constructor.py", line 661, in Polyhedron
[dochtml] [categorie]     return parent(Vrep, Hrep, convert=convert, verbose=verbose)
[dochtml] [categorie]   File "sage/structure/parent.pyx", line 900, in sage.structure.parent.Parent.__call__ (build/cythonized/sage/structure/parent.c:9365)
[dochtml] [categorie]     return mor._call_with_args(x, args, kwds)
[dochtml] [categorie]   File "sage/structure/coerce_maps.pyx", line 180, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_with_args (build/cythonized/sage/structure/coerce_maps.c:5153)
[dochtml] [categorie]     raise
[dochtml] [categorie]   File "sage/structure/coerce_maps.pyx", line 175, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_with_args (build/cythonized/sage/structure/coerce_maps.c:5041)
[dochtml] [categorie]     return C._element_constructor(x, *args, **kwds)
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/parent.py", line 597, in _element_constructor_
[dochtml] [categorie]     return self.element_class(self, Vrep, Hrep, **kwds)
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/base.py", line 278, in __init__
[dochtml] [categorie]     self._init_from_Vrepresentation(vertices, rays, lines, **kwds)
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/backend_field.py", line 193, in _init_from_Vrepresentation
[dochtml] [categorie]     H = Vrep2Hrep(self.base_ring(), self.ambient_dim(), vertices, rays, lines)
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/double_description_inhomogeneous.py", line 457, in __init__
[dochtml] [categorie]     DD = Algorithm(A).run()
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/double_description.py", line 763, in run
[dochtml] [categorie]     DD.add_inequality(a)
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/double_description.py", line 714, in add_inequality
[dochtml] [categorie]     if not self.are_adjacent(rp, rn):
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/double_description.py", line 446, in are_adjacent
[dochtml] [categorie]     Z = self.zero_set(r1).intersection(self.zero_set(r2))
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/double_description.py", line 375, in zero_set
[dochtml] [categorie]     t.update(self.A[i] for i in range(n,len(self.A)) if self.A[i].inner_product(ray) == self.zero)
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/geometry/polyhedron/double_description.py", line 375, in <genexpr>
[dochtml] [categorie]     t.update(self.A[i] for i in range(n,len(self.A)) if self.A[i].inner_product(ray) == self.zero)
[dochtml] [categorie]   File "sage/structure/element.pyx", line 1109, in sage.structure.element.Element.__richcmp__ (build/cythonized/sage/structure/element.c:10346)
[dochtml] [categorie]     return (<Element>self)._richcmp_(other, op)
[dochtml] [categorie]   File "sage/structure/element.pyx", line 1113, in sage.structure.element.Element._richcmp_ (build/cythonized/sage/structure/element.c:10452)
[dochtml] [categorie]     cpdef _richcmp_(left, right, int op):
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/rings/qqbar.py", line 5323, in _richcmp_
[dochtml] [categorie]     return bool(self) == (op == op_NE)
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/rings/qqbar.py", line 3951, in __bool__
[dochtml] [categorie]     c = cmp_elements_with_same_minpoly(left, right, left.minpoly())
[dochtml] [categorie]   File "/opt/sage/local/lib/python3.9/site-packages/sage/rings/qqbar.py", line 2770, in cmp_elements_with_same_minpoly
[dochtml] [categorie]     raise RuntimeError('a = {}\nb = {}\np = {}'.format(a, b, p))
[dochtml] [categorie] RuntimeError: a = 2.917983368234029?e15
[dochtml] [categorie] b = 2.917983368234029?e15
[dochtml] [categorie] p = x^6 - 5835966736468056*x^5 + 2658455991569831813923974927379870544*x^4 + 2658455991569831814199401327502424704*x^3 + 2658455991569831809001982851260652032*x^2 + 253512790118400*x + 4096
[dochtml] [cpython  ] building [inventory]: targets for 8 source files that are out of date
[dochtml] [cpython  ] updating environment: [new config] 8 added, 0 changed, 0 removed
[dochtml] [cpython  ] The inventory files are in local/share/doc/sage/inventory/en/reference/cpython.
[dochtml] Build finished. The built documents can be found in /opt/sage/local/share/doc/sage/inventory/en/reference/cpython
[dochtml] cd /opt/sage && ./sage --docbuild --no-pdf-links reference/cryptography inventory --no-prune-empty-dirs
[dochtml] [categorie] The inventory files are in local/share/doc/sage/inventory/en/reference/categories.
[dochtml] Error building the documentation.
[dochtml] Traceback (most recent call last):
[dochtml]   File "/usr/lib/python3.9/runpy.py", line 197, in _run_module_as_main
[dochtml]     return _run_code(code, main_globals, None,
[dochtml]   File "/usr/lib/python3.9/runpy.py", line 87, in _run_code
[dochtml]     exec(code, run_globals)
[dochtml]   File "/opt/sage/local/lib/python3.9/site-packages/sage_docbuild/__main__.py", line 2, in <module>
[dochtml]     main()
[dochtml]   File "/opt/sage/local/lib/python3.9/site-packages/sage_docbuild/__init__.py", line 1813, in main
[dochtml]     builder()
[dochtml]   File "/opt/sage/local/lib/python3.9/site-packages/sage_docbuild/__init__.py", line 821, in _wrapper
[dochtml]     getattr(DocBuilder, build_type)(self, *args, **kwds)
[dochtml]   File "/opt/sage/local/lib/python3.9/site-packages/sage_docbuild/__init__.py", line 133, in f
[dochtml]     runsphinx()
[dochtml]   File "/opt/sage/local/lib/python3.9/site-packages/sage_docbuild/sphinxbuild.py", line 322, in runsphinx
[dochtml]     sys.stderr.raise_errors()
[dochtml]   File "/opt/sage/local/lib/python3.9/site-packages/sage_docbuild/sphinxbuild.py", line 257, in raise_errors
[dochtml]     raise OSError(self._error)
[dochtml] OSError: /opt/sage/local/lib/python3.9/site-packages/sage/categories/finite_coxeter_groups.py:docstring of sage.categories.finite_coxeter_groups.FiniteCoxeterGroups.ParentMethods.permutahedron:50: WARNING: Exception occurred in plotting finite_coxeter_groups-1
[dochtml] 
[dochtml]     Note: incremental documentation builds sometimes cause spurious
[dochtml]     error messages. To be certain that these are real errors, run
[dochtml]     "make doc-clean" first and try again.
[dochtml] [cryptogra] building [inventory]: targets for 22 source files that are out of date
[dochtml] [cryptogra] updating environment: [new config] 22 added, 0 changed, 0 removed

[isuruf]

Do you have a recent log from Github actions CI?

[chapoton]

bump to 9.6

[isuruf]

Can't reproduce on sage 9.5