[Python-talk] Generator Question

[Kent Johnson]

On Fri, Aug 14, 2009 at 5:19 PM, <bruce.labitt at autoliv.com> wrote:
> Question about the last stage, what I would call the consumer of the
> generator data.
>
> I have written make_array, compute_fft, and compute_power.  Instead of
> using the
> routine optimize (which I have not written yet), I want to test what I
> have.
>
> I am trying to write a function called max_power.
>
> The output of the function is the element by element column maximum of the
> arrays in powers.
>
> Consider the following as a matrix
>
> [ 0 1 2 3 4]
> [ 5 6 7 8 9]
> [10 0 1 9 7]
>
>  10 6 7 9 9  <== column max
>
> There is a numpy function called maximum
> It returns an array c whose ith element is the maximum of (ai, bi)
>
> c = maximum( a, b ), ci = max(ai, bi) for i in c
>
> The output of max_power should be one array that is the column maximum of
> the matrix
>
> [ powers row 0 ] first iteration of generator
> [ powers row 1 ] 2nd
>    .
>    .
>    .
> [ powers row last ] last
>
>
> So I want max_power to consume all of the data from the previous stages
> and only return
> a single row which is the column by column maximum.
>
> Now there really isn't a real matrix here, just a series of arrays (or
> rows) that are output
> by the previous generator.

OK, so you need a function that consumes a sequence of row arrays and
computes the element-by-element maxima. If you have
powers = ( <some generator for the powers arrays> )

and maximum(a, b) will take the desired maximum of two elements of
powers, then I think the result you want is
max_power = reduce(maximum, powers)

Kent