#19551: Basic failures in projective product morphisms
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Reporter: bhutz | Owner:
Type: defect | Status: needs_work
Priority: minor | Milestone: sage-6.10
Component: algebraic | Resolution:
geometry | Merged in:
Keywords: product | Reviewers: Ben Hutz
projective morphism | Work issues:
Authors: Tom Salvi, Joe | Commit:
Eisner | 2858087c035d7b533419ea04666c810d7ae10d67
Report Upstream: N/A | Stopgaps:
Branch: |
u/tsalvi/ticket/19551 |
Dependencies: |
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Changes (by bhutz):
* status: needs_review => needs_work
* reviewer: => Ben Hutz
Comment:
A couple comments:
- There is a test failure in morphism.py. That test is checking if the map
is a non-morpism, but the map is actually poorly defined. So correct the
map to still be a non-morphism, but a valid map.
- I think we need at least some basic input checking in __call__, e.g.
that the codomain of the point is in the domain of the function, otherwise
examples like the following are badly behaved:
{{{
PP.<t0,t1,t2,t3,t4>=ProductProjectiveSpaces([2,1],ZZ)
Q=PP([1,1,1,2,1])
Z.<a,b,x,y,z> = ProductProjectiveSpaces([1,2],ZZ)
H = End(Z)
f = H([a^3,b^3+a*b^2,x^2,y^2-z^2,z*y])
f(Q)
}}}
While we are fixing __call__, I think you should add a test for the
parameter `check` as well, such as the following:
{{{
PP.<x,y,z,u,v,w,s,t>=ProductProjectiveSpaces(QQ,[3,3])
HP=End(PP)
g=HP([4*v*x^2,2*w*y^2,2*v*z^2,2*s*x*y,v^2,w^2,3*s*v,t^2])
P=PP([1,1,2,1,1,0,3,1])
g(P,check=False)
}}}
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Ticket URL: <http://trac.sagemath.org/ticket/19551#comment:4>
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