William (stein),

You mentioned in the thread below on the speeds of the other packages
for poly mult that you use number fields of high degree when computing
modular forms. Are these number fields as such, or local fields?

If they are number fields, then what degree fields do you compute in.
I've timed MAGMA and Pari at this and MAGMA seems hopelessly slow for
fields of degree say 15 or higher. Pari occasionally manages a degree
17 and I imagine on a fast machine might do slightly better.

The limitation in Pari appears to be factoring the discriminant, which
for a degree 24 field might have a 5000 bit discriminant. After that I
believe the matrix algebra would eventually finish, even though it
takes quite some time. But Obviously a 5000 bit integer will never
factor unless it has many small factors (in which case the elliptic
curve method ala GMP-ECM would benefit it greatly, since Pari's own ECM
is a bit outdated). But it is not clear to me that for a generic number
field, you actually can expect the discriminant to have many small
factors.

At any rate, how are you working with number fields of "large degree".
Are they abelian, Probably that helps. I don't know what the situation
is for those.

Also, you didn't mention how fast polynomial multiplication helps. Do
you mean just in multiplying elements of the number field expressed as
polynomials in powers of the generator together.

Bill.

P.S: Check out my timings for FLINT's Karatsuba in the thread below
where you posted your timings. :-)


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