Misc. re: 2.6.7

I've checked the version of maxima comiled with 2.6.8pre
I don't know if it is interesting or not.
The old test for the Cartan identities with 2.6.7 showed :

(%i9) canform(liediff(v, extdiff(a([i1, i2, i3, i4, i5]), i6))
                            - extdiff(liediff(v, a([i1, i2, i3, i4, i5])), 
i6))
Evaluation took 7.20 seconds (8.55 elapsed)
(%o9)                                  0
(%i10) canform(liediff(v, extdiff(a([i1, i2, i3, i4, i5, i6]), i7))
                        - extdiff(liediff(v, a([i1, i2, i3, i4, i5, i6])), 
i7))
Evaluation took 70.61 seconds (616.13 elapsed)
(%o10)                                 0

Now,  on the same machine with the RAM enlarged from 256 -> 512Mb, with 2.6.8 
I've get:

(%i9) canform(liediff(v, extdiff(a([i1, i2, i3, i4, i5]), i6))
                            - extdiff(liediff(v, a([i1, i2, i3, i4, i5])), 
i6))
Evaluation took 27.70 seconds (27.89 elapsed)
(%o9)                                  0
(%i10) canform(liediff(v, extdiff(a([i1, i2, i3, i4, i5, i6]), i7))
                        - extdiff(liediff(v, a([i1, i2, i3, i4, i5, i6])), 
i7))
Evaluation took 278.42 seconds (279.50 elapsed)
(%o10)                                 0


best regards
Valery