workaround for primary decomposition in quotient rings

[seelisch]

Mail from March 27 to Franziska Hinkelmann: proposal for workaround for primary decomposition in quotient rings:

Dear Franziska,

at current state, the Singular implementation for primary decomposition applies to polynomial rings with a global monomial order, but not to quotient rings. To reduce the quotient ring case to the polynomial ring case, proceed as follows:

LIB"primdec.lib"; ring R = 0, (x, y), dp; dp faster than lp

ideal I = x2-y; ideal C = y-1; list pr = primdecSY(I+C); pd of I+C over R

primdecGTZ often faster

qring qR = std(I); list PSI = imap(R,pr); map into R/I for further work

Your letter reminded us, that we should implement this short work around into Singular. It will be available with future versions. Thank you for pointing this out to us.

Best regards, Wolfram Decker