Puiseoux lift bug

[edgarcosta]

> R<X,Y,Z>:=PolynomialRing(RationalsExtra(600),3);
> C:=PlaneCurve(2*Y^4+Y^2*(4*X^2-6*Z^2)+4*X^4+6*X^3*Z+X*Z^3+3*Z^4);
> CertifiedEndomorphismAlgebra(C: Geometric := true);

CertifiedEndomorphismAlgebra(
    X: Curve over Rational Field defined by X^4 + 3/2*X^3*Z + X^2*Y...
)
Correspondence(
    X: Curve over Number Field with defining polynomial x^24 - 12*x...,
    Y: Curve over Number Field with defining polynomial x^24 - 12*x...,
    mor: [* [1/11779203072*(-99088209*$.1^23 + 1071743080*$.1^22 - 58...
)
CantorFromMatrixAmbientSplit(
    X: Curve over Number Field with defining polynomial x^24 - 12*x...,
    P0: (-1 : 0 : 1),
    Y: Curve over Number Field with defining polynomial x^24 - 12*x...,
    Q0: (-1 : 0 : 1),
    M: [1/11779203072*(-99088209*$.1^23 + 1071743080*$.1^22 - 58214...
)
InitializedIterator(
    X: Curve over Number Field with defining polynomial x^24 - 12*x...,
    Y: Curve over Number Field with defining polynomial x^24 - 12*x...,
    M: [1/23558406144*(89813505*$.1^23 - 931190380*$.1^22 + 4800945...,
    n: 6
)
PuiseuxLeadingExponent(
    M: [1/23558406144*(89813505*$.1^23 - 931190380*$.1^22 + 4800945...,
    echelon_exps: [ 1, 2, 3 ]
)
In file
"/home/kedlaya/code/CHIMP/endomorphisms/endomorphisms/magma/puiseux/Branches.m",
line 68, column 18:
>>     j0 := Minimum([ j : j in [1..gX] | row[j] ne 0 ]);
                    ^
Runtime error in 'Minimum': Argument 1 is not non-empty


> CertifiedEndomorphismAlgebra(C: Geometric:=true, Al:="Divisor");

CertifiedEndomorphismAlgebra(
X: Curve over Rational Field defined by X^4 + 3/2*X^3*Z + X^2*Y...
)
Correspondence(
X: Curve over Number Field with defining polynomial t^24 - 12*t...,
Y: Curve over Number Field with defining polynomial t^24 - 12*t...,
mor: [* [1/11779203072*(-99088209*$.1^23 + 1071743080*$.1^22 - 58...
)
DivisorFromMatrixAmbientSplit(
X: Curve over Number Field with defining polynomial t^24 - 12*t...,
P0: (-1 : 0 : 1),
Y: Curve over Number Field with defining polynomial t^24 - 12*t...,
Q0: (-1 : 0 : 1),
M: [1/11779203072*(-99088209*$.1^23 + 1071743080*$.1^22 - 58214...
)
InitializedIterator(
X: Curve over Number Field with defining polynomial t^24 - 12*t...,
Y: Curve over Number Field with defining polynomial t^24 - 12*t...,
M: [1/23558406144*(89813505*$.1^23 - 931190380*$.1^22 + 4800945...,
n: 6
)
PuiseuxLeadingExponent(
M: [1/23558406144*(89813505*$.1^23 - 931190380*$.1^22 + 4800945...,
echelon_exps: [ 1, 2, 3 ]
)
In file "/Users/edgarcosta/projects/CHIMP/endomorphisms/endomorphisms/magma/puiseux/Branches.m", line 68, column 18:
>>     j0 := Minimum([ j : j in [1..gX] | row[j] ne 0 ]);
                    ^
Runtime error in 'Minimum': Argument 1 is not non-empty

reported by @kedlaya