Should we extend flow algorithm to MetaGraphs.jl? about metagraphs.jl HOT 5 CLOSED

They should just work as long as you've got a :weight attribute on the edges.

(:weight is the default attribute for weights, you can use weightfield!() to change it.)

from metagraphs.jl.

@sbromberger Thanks, I was not even aware, could you point to the code part(s) that make(s) it work?
I have an incoming PR for a flow-like algorithm in LG, and I would definitively love to have it work with MetaGraphs from the start.

(I will close the issue as soon as I have no more reason to bother you, sorry)

from metagraphs.jl.

Sure. Take a look at the README.md towards the end to see how the weights work in MetaGraphs:

# using weights
julia> mg = MetaGraph(CompleteGraph(3))
{3, 3} undirected Int64 metagraph with Float64 weights defined by :weight (default weight 1.0)

julia> enumerate_paths(dijkstra_shortest_paths(mg, 1), 3)
2-element Array{Int64,1}:
 1
 3

julia> set_prop!(mg, 1, 2, :weight, 0.2)
Dict{Symbol,Float64} with 1 entry:
  :weight => 0.2

julia> set_prop!(mg, 2, 3, :weight, 0.6)
Dict{Symbol,Float64} with 1 entry:
  :weight => 0.6

julia> enumerate_paths(dijkstra_shortest_paths(mg, 1), 3)
3-element Array{Int64,1}:
 1
 2
 3

Then, in https://github.com/JuliaGraphs/MetaGraphs.jl/blob/130f60c0fab66fa183da1cf65bfbae93f6b66cc4/src/MetaGraphs.jl#L108, we override weights(), which is used by any LightGraphs function that can handle weights (graph types can override the default "all weights = 1" structure, which is what we do here.) See https://github.com/JuliaGraphs/LightGraphs.jl/blob/f8b5589bd5bef1d71a3806082f125f8f1cb67d8b/src/centrality/closeness.jl#L14 for an example.

That said, the existing flow algorithms don't use weights, they use capacity and residual matrices. We might want to revisit that.

from metagraphs.jl.

That said, the existing flow algorithms don't use weights, they use capacity and residual matrices. We might want to revisit that.

I think it would be really nice.

As for my incoming PR, it also uses weights on the vertices, so I will have to be creative, but I will make it compatible with MetaGraphs. Should we let the issue opened while flow algorithms are not yet using weights?

from metagraphs.jl.

Should we let the issue opened while flow algorithms are not yet using weights?

Not here, but there should probably be an issue in LightGraphs for discussion.

from metagraphs.jl.