I’m trying to implement the Rhea C++ constraint solving algorithm in Julia as a learning project. I’m simply translating the original source as far as I’m able into something that makes sense in Julia. I have implemented part of the unit tests and at the current state they fail with a StackOverflow…

I would try making [image] jules: ==(::variable{Float64}, ::variable{Float64}) or one of its callers print its arguments (eg @show, @info), so that I could isolate a deterministic example.

I’ve put @show into an inner constructor of expression and it prints new{T}(c, t) = expression{variable{Float64}}(0.0, Dict(variable{Float64}(3.0)=>1.0)) new{T}(c, t) = expression{variable{Float64}}(0.0, Dict(variable{Float64}(2.0)=>1.0)) new{T}(c, t) = expression{variable{Float64}}(0.0, Dict(varia…

[image] jules: Is it a problem to use mutable structs as keys in a Dict? If you happen to mutate them after inserting as keys, yes. If your algorithm allows (immutable) structs, try to organize it with those. This may have performance benefits, and usually leads to much cleaner code.

[image] Tamas_Papp: If you happen to mutate them after inserting as keys, yes. Are you sure? I just read that the hash function for mutable structs operates on objectid, which should be fine as the address of the variables shouldn’t change, that’s kind of their “identity”

[image] Tamas_Papp: If you happen to mutate them after inserting as keys, yes. I thought that for mutable structs, the hash was based on memory address, not contents, in which case it wouldn’t matter if you change them.

Don’t rely on that, that’s an implementation detail. And you can get into trouble, eg julia> mutable struct Foo a::Int end julia> d = Dict() Dict{Any,Any} with 0 entries julia> a = Foo(1) Foo(1) julia> d[a] = "test" "test" julia> a.a = 4 4 julia> d Dict{Any,Any} with 1 entry: F…

The thing that still doesn’t make sense to me is, how can the error appear only sometimes if I have exactly the same testset every time? Many times it runs fine

[image] jules: how can the error appear only sometimes if I have exactly the same testset every time? Many times it runs fine [image] Understanding Dict General Usage Hi everyone. I am coming from python background. In python, dictionary keys cannot be mutable beca…

What other data structure could I use in Julia? The c++ source uses unordered_map to keep track of many std::make_shared<float_variable>s. I thought the Dict could play the role of the unordered map and the mutable structs act as shared variables

I think your best option is figuring out a way that does not mutate keys.

How to debug a non-deterministic StackOverflowError?

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Tamas_Papp May 29, 2019, 11:08am 9

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How to debug a non-deterministic StackOverflowError?

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