On Sat, Mar 29, 2014 at 8:55 AM, <[email protected]> wrote: > On Sat, Mar 29, 2014 at 7:31 AM, <[email protected]> wrote: > > On Sat, Mar 29, 2014 at 12:12 AM, Jaime Fernández del Río > > <[email protected]> wrote: > >> Hi, > >> > >> I have submitted a PR (https://github.com/numpy/numpy/pull/4568) that > speeds > >> up `np.vander` by using accumulated multiplication instead of > exponentiation > >> to compute the Vandermonde matrix. For largish matrices the speed-ups > can be > >> quite dramatic, over an order of magnitude. > >> > >> Julian has raised concerns on numerical stability and loss of precision, > >> which don't seem to be all that relevant. Do speak up if you think > >> otherwise. > >> > >> We are also discussing replacing a recently added kwarg, "order", which > now > >> accepts a string, either "increasing" or "decreasing", to indicate the > >> ordering of the matrix columns. This was not present in 1.8, so can > still be > >> modified. The proposal is to replace it with a "reversed" boolean flag. > >> Unfortunately, the return of np.vander in 1.8 and before is the opposite > >> (i.e. its reversed) from the standard definition, which has powers > >> increasing from left to right. So it is not clear what the reversed > keyword > >> should refer to: > >> > >> 1. If it refers to the standard definition, then it would default to > False > >> for backwards compatibility, but be consistent with the conventional > >> definition. > >> > >> 2. If it refers to the existing behavior of numpy's vander, then it > would > >> default to True, and not be consistent with the conventional definition. > >> > >> I prefer option 1, but would like to hear other's opinions. Which could > of > >> course include naming the boolean flag more ingeniously, or keeping the > >> string flag. If he's reading, I'd specially like to hear Warren > Weckesser's > >> thoughts, as he is the one who added the "order" kwarg. > > > > "order" is not a good name, I would find it very confusing (I'm > > usually mixing up order and degree) > > http://en.wikipedia.org/wiki/Order_of_a_polynomial > > > > how about calling the keyword "increasing=False" ? > > which would avoid defining what it's reversed against. > > Obviously I didn't read the PR before answering. > > But it shows that `increasing` might be obvious, or that Warren and I > think the same way. >
Great minds think alike! It seems we have a 4 people consensus, "increasing" it is. Thanks for the feedback. Jaime -- (\__/) ( O.o) ( > <) Este es Conejo. Copia a Conejo en tu firma y ayúdale en sus planes de dominación mundial.
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