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TestIdeals :: isFinjective(..., CanonicalStrategy => ...)

isFinjective(..., CanonicalStrategy => ...) -- specify a strategy for isFinjective

Synopsis

Description

If CanonicalStrategy=>Katzman which is the default behavior, then the Frobenius action on the top local cohomology (bottom Ext) is computed via the method of Katzman. If it is set to anything else, it is simply brute forced in Macaulay2 using the fuctoriality of Ext. CanonicalStrategy=>Katzman typically is much faster.

i1 : R = ZZ/5[x,y,z]/ideal(y^2*z + x*y*z-x^3)

o1 = R

o1 : QuotientRing
i2 : time isFinjective(R)
     -- used 0.0146254 seconds

o2 = true
i3 : time isFinjective(R, CanonicalStrategy=>null)
     -- used 0.771992 seconds

o3 = true

Further information