Error in kernel function

[Charley Crissman]

I'm using the PushForward package (currently hiding in Schubert2/pushFwd.m2) for some work in Schubert2.  I'm getting an error in the kernel function that I don't understand:

/usr/local/share/Macaulay2/Core/matrix3.m2:45:14:(1):[7]: error: assertion failed
/usr/local/share/Macaulay2/Core/matrix3.m2:45:14:(1):[7]: --entering debugger (type help to see debugger commands)
/usr/local/share/Macaulay2/Core/matrix3.m2:45:14-45:52: --source code:
             assert( degreesRing R === degreesRing G );

Here's what the program state looks like:

ii17 : R -- is QQ[h]/h^3

oo17 = B

oo17 : QuotientRing

ii18 : G

         QQ[X , X , X ]
             0   1   2
oo18 = ------------------
         3   6     3   2
       (X , X , X X , X )
         0   2   1 2   1

oo18 : QuotientRing

ii19 : degreesRing R

oo19 = ZZ[T]

oo19 : PolynomialRing

ii20 : degreesRing G

oo20 = ZZ[T]

oo20 : PolynomialRing


The error is arising when I call

kernel map(B^1,A^1,f,matB)

with B = QQ[h]/h^3 as above, matB = |1| over B, and the rest of the state:

ii16 : A

          QQ[E , x]
              0
oo16 = --------------
         6     3   2
       (x , E x , E )
             0     0

oo16 : QuotientRing

ii17 : f

                QQ[E , x]
                    0
oo17 = map(B,--------------,{0, h})
               6     3   2
             (x , E x , E )
                   0     0


Any advice on getting around this error?  I don't know what I could do to construct my rings differently so that they would have degreesRings that would compare as equal under ===

-Charley

[Grayson, Daniel R.]

On Dec 2, 2011, at 8:10 PM, Charley Crissman wrote:

> I'm using the PushForward package (currently hiding in Schubert2/pushFwd.m2) for some work in Schubert2. I'm getting an error in the kernel function that I don't understand:
>
> /usr/local/share/Macaulay2/Core/matrix3.m2:45:14:(1):[7]: error: assertion failed
> /usr/local/share/Macaulay2/Core/matrix3.m2:45:14:(1):[7]: --entering debugger (type help to see debugger commands)
> /usr/local/share/Macaulay2/Core/matrix3.m2:45:14-45:52: --source code:
> assert( degreesRing R === degreesRing G );

...

Hi, Charley.

I tried to reproduce the problem but couldn't.

Could you send a file containing code that producess the error to me at d...@math.uiuc.edu ? I'll
take a look at it. (Anything checked into the trunk you can assume I'll have.)

I'm traveling, so expect a slow response.

[Charley Crissman]

I've got it figured out. It turns out that I had a bug somewhere else
that was causing the ring A above to have negatively graded elements.
Thanks for taking a look!

-C

[Charley Crissman]

However: the following will produce the same issue:

C = QQ[x]
A = C[y]
B = C[z]
f = map(B,A,{z})
matB = matrix{{1_B}}
kernel map(B^1, A^1, f, matB)

In this case the two degreesRings are actually different, so it's no
surprise the assertion fails. I know that kernel is buggy about tower
rings; I'm not sure what ought to be done here. It's a bit strange to
me that kernel happily works with other tower rings; see for example
the last test in Schubert2/blowup-test.m2 .

-C

[Grayson, Daniel R.]

It will take some thought to figure out what the code ought to do
in your case. Meanwhile, do you need the multidegrees, or can you
make do with adding Join=>false to the creation of A and of B?

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