Bug #1634
Unexpected or unhelpful error using GroebnerFanIdeals
Description
Here is the troublesome input: it throws ArgTooBig
/**/ use QQ[x,y,z,t]; /**/ I := ideal(y^9*t-x, x^9*y-z^9*t, x^10-z*t, x*z^9-t^9); /**/ SetVerbosityLevel(20); /**/ GF := GroebnerFanIdeals(I); *..*..*...*...*...*.--> ERROR: Argument to a numerical function too large (value would be too big) --> [CoCoALib] OrdvArith::MatrixOrderingMod32749Impl ctor --> WHERE: at line 89 (column 8) of GroebnerFan.cpkg5 --> P := NewPolyRing(CoeffRing(RingOf(I)), IndetSymbols(RingOf(I)), M, 0); --> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Related issues
History
#1
Updated by John Abbott over 2 years ago
Updated by I find the error quite surprising; at least the particular error that was thrown.
I had half expected there to be some problem (e.g. too many different ideals).
Is it just an overly entry in the order matrix?
Anyway, a more helpful message would be nice.
#2
Updated by John Abbott over 2 years ago
- Related to Design #984: GroebnerFanIdeals: order matrices sometimes have "large" entries added
#3
Updated by John Abbott over 2 years ago
Here is a simpler failing example: I have just reduced the exponents
/**/ I := ideal(y^4*t-x, x^4*y-z^4*t, x^5-z*t, x*z^4-t^4);
If I reduce the exponents by 1 to 3 or 4 then the GFan computation completes.
#4
Updated by Anna Maria Bigatti over 2 years ago
Updated by The problem is that the ordering matrix has some big entry (after being converted into a matrix with positive entries).
Indeed I find the error message too verbose. I'd change "ERROR: Argument to a numerical function too large (value would be too big)" into:
ERROR: Number too big