[sage-devel] Re: dimension() broken for ideals?
This is now ticket #18374
El miércoles, 6 de mayo de 2015, 17:47:54 (UTC+2), Jakob Kroeker escribió:
It is definitely a bug in the dimension method.
could you open a ticket and post the link here?
Am Sonntag, 3. Mai 2015 15:25:13 UTC+2 schrieb mmarco:
It is definitely a bug in the dimension method.
If singular can handle the ring, sage asks singular to compute the
dimension, which does correctly (the -1 is the singular convention for
empty varieties).
The problem is that when the field is not supported by singular (which
happens with QQbar or finite fields of characteristic bigger than 2^31) ,
then sage falls back to its own toy implementation. In that case, it
appears that the empty case is not treated separatedly than the zero
dimensional case.
El viernes, 1 de mayo de 2015, 21:18:55 (UTC+2), gjorgen...@my.fit.edu
escribió:
Hi,
For the following ideal, dimension() returns 0,
{{{
R.s0,s1=QQbar[]
I=R.ideal([ s0 + 1, s0*s1 + s0 + s1 + 1, (-2)*s0 + 1, (-10)*s1 + 5,
5*s0^2 + 10*s0*s1 ])
I.dimension()
}}}
but its variety is empty.
Also for any other ring, dimension() returns -1 for this ideal. Is this
a bug with dimension()? The documentation for dimension() doesn't seem to
mention the -1 case.
It provides the following example,
{{{
R.x,y = PolynomialRing(GF(2147483659),order='lex')
I = R.ideal([x*y,x*y+1])
I.dimension()
}}}
which yields dimension 0 for the ideal, yet the corresponding variety is
empty.
What is the expected behavior for dimension()? When the variety of the
ideal in question has no points is dimension() always supposed to return -1?
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[sage-devel] Re: dimension() broken for ideals?
It is definitely a bug in the dimension method.
could you open a ticket and post the link here?
Am Sonntag, 3. Mai 2015 15:25:13 UTC+2 schrieb mmarco:
It is definitely a bug in the dimension method.
If singular can handle the ring, sage asks singular to compute the
dimension, which does correctly (the -1 is the singular convention for
empty varieties).
The problem is that when the field is not supported by singular (which
happens with QQbar or finite fields of characteristic bigger than 2^31) ,
then sage falls back to its own toy implementation. In that case, it
appears that the empty case is not treated separatedly than the zero
dimensional case.
El viernes, 1 de mayo de 2015, 21:18:55 (UTC+2), gjorgen...@my.fit.edu
escribió:
Hi,
For the following ideal, dimension() returns 0,
{{{
R.s0,s1=QQbar[]
I=R.ideal([ s0 + 1, s0*s1 + s0 + s1 + 1, (-2)*s0 + 1, (-10)*s1 + 5,
5*s0^2 + 10*s0*s1 ])
I.dimension()
}}}
but its variety is empty.
Also for any other ring, dimension() returns -1 for this ideal. Is this a
bug with dimension()? The documentation for dimension() doesn't seem to
mention the -1 case.
It provides the following example,
{{{
R.x,y = PolynomialRing(GF(2147483659),order='lex')
I = R.ideal([x*y,x*y+1])
I.dimension()
}}}
which yields dimension 0 for the ideal, yet the corresponding variety is
empty.
What is the expected behavior for dimension()? When the variety of the
ideal in question has no points is dimension() always supposed to return -1?
--
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[sage-devel] Re: dimension() broken for ideals?
It is definitely a bug in the dimension method.
If singular can handle the ring, sage asks singular to compute the
dimension, which does correctly (the -1 is the singular convention for
empty varieties).
The problem is that when the field is not supported by singular (which
happens with QQbar or finite fields of characteristic bigger than 2^31) ,
then sage falls back to its own toy implementation. In that case, it
appears that the empty case is not treated separatedly than the zero
dimensional case.
El viernes, 1 de mayo de 2015, 21:18:55 (UTC+2), gjorgen...@my.fit.edu
escribió:
Hi,
For the following ideal, dimension() returns 0,
{{{
R.s0,s1=QQbar[]
I=R.ideal([ s0 + 1, s0*s1 + s0 + s1 + 1, (-2)*s0 + 1, (-10)*s1 + 5, 5*s0^2
+ 10*s0*s1 ])
I.dimension()
}}}
but its variety is empty.
Also for any other ring, dimension() returns -1 for this ideal. Is this a
bug with dimension()? The documentation for dimension() doesn't seem to
mention the -1 case.
It provides the following example,
{{{
R.x,y = PolynomialRing(GF(2147483659),order='lex')
I = R.ideal([x*y,x*y+1])
I.dimension()
}}}
which yields dimension 0 for the ideal, yet the corresponding variety is
empty.
What is the expected behavior for dimension()? When the variety of the
ideal in question has no points is dimension() always supposed to return -1?
--
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sage-devel group.
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to sage-devel+unsubscr...@googlegroups.com.
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