Basic failures in projective product morphisms

[bhutz]

The following are simple bugs in projective product morphisms:

PP.<x,y,z,u,v,w>=ProductProjectiveSpaces(QQ,[1,1,1])
HP=End(PP)
f=HP([v*x^2,w*y^2,z^2,u^2,v^2,w^2])
Q=PP([0,1,1,1,1,0])
f(Q)

R.<s,t>=PolynomialRing(QQ)
Z.<a,b,x,y,z> = ProductProjectiveSpaces([1,2],QQ)
P.<u,v,w,s,t,r>=ProductProjectiveSpaces([3,1],QQ)
H =Hom(Z,P)
f = H([a^2,b^2,a^2,a*b,a*x,b*z])

the following should fail (not multihomogeneous) but passes

Z.<a,b,c,x,y,z> = ProductProjectiveSpaces([1,3],QQ)
P.<u,v,w,s,t,r>=ProductProjectiveSpaces([2,2],QQ)
H =Hom(Z,P)
f = H([a^2,b^2,c^2,x^2,y^2,z^2])

[bhutz]

Call also needs some basic input checking:

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)

[tsalvi]

New commits:

​2858087

19551: fix failures in projective projects

[bhutz]

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)

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​d705d01

19551: added check and examples

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​7054db6

Merge branch 'master' into t/19551/ticket/19551

[bhutz]

Still needs some minor work:

should have spaces around the = sage: PP.<t0,t1,t2,t3,t4>=ProductProjectiveSpaces([2,1], ZZ)

On lines 12, 39, 62, 149, 388 there is terminating white space

In the functions init, call no space around = for check

2 doc test failures

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​1ded112

19551: fix issues about spacing and doctest

[bhutz]

Still needs some minor work:

should have spaces around the = sage: PP.<t0,t1,t2,t3,t4>=ProductProjectiveSpaces([2,1], ZZ)

On lines 12, 39, 62, 149, 388 there is terminating white space

In the functions init, call no space around = for check

2 doc test failures

---

New commits:

​1ded112

19551: fix issues about spacing and doctest

[jdemeyer]

Is "Joe Eisner" by chance equal to "Joseph Eisner" from #19891 and #20067?

[bhutz]

Yes, those are the same.

[kcrisman]

Also, just want to make sure that it should be "Tom Salvi" and not "Thomas P. Salvi" as you registered.