Opened 13 years ago

Closed 13 years ago

## #190 closed bug (wontfix)

# example yielding an error in resolve.lib::resolve / resolve.lib::CenterBO

Reported by: | Alberto Calabri | Owned by: | |
---|---|---|---|

Priority: | minor | Milestone: | 3-1-1 |

Component: | singular-libs | Version: | 3-1-0 |

Keywords: | resolve.lib | Cc: | pfister@… |

### Description

Dear Singular Team, when I was running Singular, I've got the following error message:

? reset in Center, please send the example to the authors. ? leaving resolve.lib::CenterBO ? leaving resolve.lib::resolve

The input commands were the following:

LIB "resolve.lib"; ring r1=32003,(x(0..4)),dp; poly f=21*x(0)3*x(3)*x(4)2+x(0)2*x(1)*x(2)2*x(4)+47*x(0)2*x(2)3*x(4)+16*x(0)2*x(3)3*x(4)+58*x(0)*x(1)3*x(3)2+71*x(0)*x(1)2*x(2)2*x(3)+30*x(0)*x(1)*x(2)2*x(3)2+38*x(0)*x(3)2*x(4)3+80*x(1)2*x(2)*x(3)*x(4)2; poly fu0=subst(f,x(0),1); ring r2=32003,(x(1..4)),dp; poly f0=imap(r1,fu0); ideal I0=f0; list L0=resolve(I0,1);

Probably you'd like to know what I am doing, so I briefly explain it. The homogeneous polynomial f defines a threefold V in P4 with five non-isolated triple points at the coordinate points (there are also five double lines and one double cubic plane curve). I want to study the singularity of V e.g. at the point P0=(1,0,0,0,0). Hence I take the chart x(0)=1 and then I tried the command "resolve". If you are interested, I may give you more information about the singularities infinitely near to P0 which I already know.

Am I making any mistake when using Singular? Perhaps "resolve" works only for isolated singularities?

I am sorry I bother you, but Singular output led me to think that you'd have liked to receive this message.

Thank you in advance for the collaboration, Alberto Calabri

P.S. and thank you very much for having done Singular and maintaining it!

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Background of Problem: algorithm is designed for characteristic zero, even theoretically there is no reason why this should work in positive characteristic

Details: The user calculated in characteristic 32003 and at one internal step in a lower coefficient ideal a leading coefficient (which would have survived in characteristic zero) becomes zero causing the error message.

Additional Remark: Up to now I did not succeed in computing the desired resolution in characteristic zero, although I used a computer with large RAM and fast processor.