Hi Travis,

On 2017-08-21, [email protected] <[email protected]> wrote:
> It is in a cython file, but it is not a cpdef method. However, I think 
> avoiding dict() (and using .iteritems() instead of items() because it is 
> Cython [so it is still Py3 compatible]) for non-sparse polynomials is good. 
> Actually, as you suggest, using the specific data structures would likely 
> be a lot faster. Do you want to start work on this, which I will happily 
> review, or do you want me to?

I am not so sure whether I will tackle specific polynomial types. However,
I think I can provide a speed up of the generic implementation: Instead
of self.dict().items(), one should work with self.list(copy=False), which
is called by self.dict() anyway, thus avoiding the overhead of constructing
a dict and its items:

   sage: R.<x> = SR[]
   sage: p = prod(x+i for i in range(60))
   sage: %timeit R([int(v)%123 for v in p.list(copy=False)])
   100 loops, best of 3: 5.13 ms per loop
   sage: %timeit p.map_coefficients(lambda z: int(z)%123)
   100 loops, best of 3: 11 ms per loop

And that's in Python (= Sage command line), not Cython.

Best regards,
Simon

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