Thank you, Páll and Yichao. To clarify:
The function is a Dijkstra shortest-paths calculation. The function can
take an optional array of distances, but should be able to function without
one (in which case the edge distances are assumed to be 1.0). I don't
really want to have to default to an array of NxN floats for the default
case, since that will cause very large graphs (say, 1 billion vertices) to
use tons of memory for no real reason.
My thought was that if I could somehow allow some other type in
"edge_dists" that would indicate "use the defaults", I could then test for
that and use (hardcoded) defaults if it's set, otherwise the data will be
an array of floats that represent edge distances.
Is there a better approach?
Thanks,
S.
On Friday, May 29, 2015 at 2:33:00 PM UTC-7, Yichao Yu wrote:
>
> On Fri, May 29, 2015 at 3:50 PM, Seth <catc...@bromberger.com
> <javascript:>> wrote:
> > I have an function that takes an optional (potentially very large)
> matrix
> > (AbstractArray{Float64,2}). I'd like to create a parameter to the
> function
> > that's EITHER this array, or a boolean (false). If I define
> >
> > edge_dists::Union(Bool, AbstractArray{Float64,2}) = false
> >
> >
> >
> > in my function declaration, would that cause significant performance
> > penalties when accessing the parameter?
>
> The function will specialize on (the type of) this parameter so there
> shouldn't be a big penalty. If you need to do something different when
> this parameter is missing and if the two cases shares a lot of code,
> this might not be a bad idea (although IMHO ::Union(Void,
> AbstractArray{Float64, 2})=nothing might be more intuitive)
>
