Understanding how to propely use SymbolicRegression.jl safe operator types

[joshkamm]

I'm working with @SoumiKDaS1701 and we're running into an issue with operator types when working on our own custom loss function. We're a bit confused about how to properly use safe_pow (and analogous types) when converting to and from SymbolicRegression.jl's node type.

How would we write the power function properly to use the types that SymbolicRegression.jl is expecting?

Here's a code snippet from our custom loss function, simplified a bit for clarity.

rho_symbolic = node_to_symbolic(tree, options; variable_names=["x1"], index_functions=true)

@syms x1
println(rho_symbolic)
println(safe_pow(x1, 2)*rho_symbolic)
# ERROR OCCURS ON THE FOLLOWING LINE
modified_rho_tree = symbolic_to_node(safe_pow(x1, 2)*rho_symbolic, options;  variable_names=["x1"])

Here's the error we're getting at the above point in the code:

exp(x1 / safe_pow(0.21631206646319978, 0.7948274113717162))
(x1^2)*exp(x1 / safe_pow(0.21631206646319978, 0.7948274113717162))

ERROR: LoadError: Operation ^ in expression not found in operations (+, *, /, -, SymbolicRegression.CoreModule.OperatorsModule.safe_pow)!
Stacktrace:
  [1] error(s::String)
    @ Base ./error.jl:35
  [2] findoperation(op::Function, ops::Tuple{typeof(+), typeof(*), typeof(/), typeof(-), typeof(safe_pow)})
    @ DynamicExpressionsSymbolicUtilsExt ~/.julia/packages/DynamicExpressions/WE72I/ext/DynamicExpressionsSymbolicUtilsExt.jl:115
  [3] convert(::Type{Node}, expr::SymbolicUtils.BasicSymbolic{Number}, operators::OperatorEnum{Tuple{…}, Tuple{…}}; variable_names::Vector{String})
    @ DynamicExpressionsSymbolicUtilsExt ~/.julia/packages/DynamicExpressions/WE72I/ext/DynamicExpressionsSymbolicUtilsExt.jl:166
  [4] convert
    @ ~/.julia/packages/DynamicExpressions/WE72I/ext/DynamicExpressionsSymbolicUtilsExt.jl:142 [inlined]
  [5] (::DynamicExpressionsSymbolicUtilsExt.var"#9#10"{Node, Vector{String}, OperatorEnum{Tuple{…}, Tuple{…}}})(x::SymbolicUtils.BasicSymbolic{Number})
    @ DynamicExpressionsSymbolicUtilsExt ~/.julia/packages/DynamicExpressions/WE72I/ext/DynamicExpressionsSymbolicUtilsExt.jl:173
  [6] iterate
    @ ./generator.jl:48 [inlined]
  [7] _collect(c::Vector{Any}, itr::Base.Generator{Vector{…}, DynamicExpressionsSymbolicUtilsExt.var"#9#10"{…}}, ::Base.EltypeUnknown, isz::Base.HasShape{1})
    @ Base ./array.jl:811
  [8] collect_similar(cont::Vector{Any}, itr::Base.Generator{Vector{Any}, DynamicExpressionsSymbolicUtilsExt.var"#9#10"{Node, Vector{…}, OperatorEnum{…}}})
    @ Base ./array.jl:720
  [9] map(f::Function, A::Vector{Any})
    @ Base ./abstractarray.jl:3371
 [10] convert(::Type{Node}, expr::SymbolicUtils.BasicSymbolic{Number}, operators::OperatorEnum{Tuple{…}, Tuple{…}}; variable_names::Vector{String})
    @ DynamicExpressionsSymbolicUtilsExt ~/.julia/packages/DynamicExpressions/WE72I/ext/DynamicExpressionsSymbolicUtilsExt.jl:171
 [11] #symbolic_to_node#15
    @ ~/.julia/packages/DynamicExpressions/WE72I/ext/DynamicExpressionsSymbolicUtilsExt.jl:235 [inlined]
 [12] symbolic_to_node
    @ ~/.julia/packages/DynamicExpressions/WE72I/ext/DynamicExpressionsSymbolicUtilsExt.jl:226 [inlined]
 [13] symbolic_to_node(eqn::SymbolicUtils.BasicSymbolic{…}, options::Options{…}; kws::@Kwargs{…})
    @ SymbolicRegressionSymbolicUtilsExt ~/.julia/packages/SymbolicRegression/Znzix/ext/SymbolicRegressionSymbolicUtilsExt.jl:32
 [14] my_custom_objective(tree::Node{…}, dataset::Dataset{…}, options::Options{…})
    @ Main ~/symbolic_regression/SymbolicRegression.jl/soumikd/scripts/model_rho.jl:38

[MilesCranmer]

Thanks for the report. I think there is actually a missing implementation here. Basically, findoperation within ext/DynamicExpressionsSymbolicUtilsExt.jl should be using declare_operator_alias so that it can find the safe operator - as otherwise it doesn't understand that ^ and safe_pow should match. Sorry this doesn't work at the moment.

Will try to fix soon. If you need this soon, I'd welcome a PR (but no pressure!).