Why is Traceur Warning: is assigned as Union{Nothing, Tuple{Int64, Int64}}?

General Usage Performance
1

Hello, I am optimizing my code. I have made all the types stable according to @code_warntype, but @trace is still giving me this warning throughout my code

Warning: is assigned as Union{Nothing, Tuple{Int64, Int64}}

The warnings are on all lines referencing graph[n].from e.g.

...
for f in graph[n].from
...
        if f == fmax
....

Here is the definition of my graph structure

struct Node
    id::Int            
    phoneme::Int       
    from::Array{Int,1} 
end

struct Graph
    nodes::Array{Node,1}
    start::Int  
    finish::Int 
end

Here is the full code with the warning lines marked with >>>

>>>for t in 2:duration
     total_total::Float64 = 0.0
>>>  for n in 1:node_count(graph)
            if n != graph.start
                # compute logsumexp([alpha(t-1,f) for f in graph[n].from])
                tl = total_likelihood(t,n,graph,alphas,scores)
                if tl > -Inf64
                    # alphas[t,n] =  max + log(sum(e.(xs -. max))) + scores[t,phoneme+1]
>>>                 alphas[t,n] = tl
                    @fastmath total_total += exp(tl)
                end
            end
        end

        #@assert total_total >= 0.0
        #@assert total_total <= 1.0

>>> alphas[t,graph.start] = log(1.0 - total_total)

What does this warning mean? Is it a problem? How do I fix it?

Thanks
Peter

1 Like
2

This is likely not a problem, due to union splitting. An iterator usually returns a Tuple or nothing, so this is a common type union seen in for loops. I’m unsure what’s happening in total_likelihood though, so I’m uncertain if the alphas line is an issue.

1 Like
3

Many thanks Jishnu