Perhaps just
f = (U,V) -> flipdim(conv(flipdim(U, 1), V), 1)
if su < sv
return f([u; zeros(eltype(u), sv - su)], v)
elseif sv < su
return f(u, [v; zeros(eltype(v), su - sv)])
else
return f(u, v)
end
?
Worth pointing out that this is not specific to SubArrays; any AbstractArray
that isn't an Array will have the same problem.
But appending elements to a SubArray is not supported.
Best,
--Tim
On Saturday, July 16, 2016 7:41:10 AM CDT CrocoDuck O'Ducks wrote:
> Hey!
>
> I started having a deeper look at the code. I tried this first fix:
>
> function xcorr_fix(u, v)
>
> su = size(u, 1)
> sv = size(v, 1)
>
> if su < sv
> # if u is a SubArray this will changes its type:
> # u = [u; zeros(eltype(u),sv-su)]
> # This avoids type instability, but forces array copy:
> U = [u; zeros(eltype(u), sv - su)]
> elseif sv < su
> # See above:
> V = [v; zeros(eltype(v), su - sv)]
> else
> U = collect(u)
> V = collect(v)
> end
>
> flipdim(conv(flipdim(U, 1), V), 1)
>
> end
>
> This appears to be somewhat effective, but there are few problems:
>
> - It defeats the purpose of passing views to the function, as a copy of
> the parent arrays is performed. Is that right?
> - Passing SubArrays to conv() seems to produce type instability of p and
> y variables.
>
> Which makes me think that first conv() should be fixed (maybe adding a
> method for the Real signals case?). Second, I feel like views should be
> allowed to go all the way to fft() in order to have a performance boost by
> using them. Is there any way to append elements through SubArrays? I tried
> append!(), insert!() and push!() but none worked... Maybe I could overwrite
> to the input SubArrays new SubArrays of this kind?
>
>
> sub([u.parent; zeros(whatever_pad_length)], :, 1)
>
>
> I guess I will make more experiments to get comfortable with SubArrays. Any
> suggestion is welcome!
