Would it be fun to have a thread where people share really fancy one liners? I think so - I think it’d be a great way to show off some of Julia to newcomers but also share some cool code. I’ll kick the thread off with 2-3, """ SquareEuclideanDistance(X) Returns the squared Grahm aka the euclide…

You can also use my pkg Reduce.jl for that if you want symbolic optimized common sub-expressions julia> using Reduce; load_package(:scope) julia> Algebra.optimize(:(z = a^2*b^2+10*a^2*m^6+a^2*m^2+2*a*b*m^4+2*b^2*m^6+b^2*m^2)) quote g40 = b * a g44 = m * m g41 = g44 * b * b g42 = g4…

I am a little stuck on this because I agree with both of you. In machine learning and physics there are often large block matrices where certain computations are repeated. So defining a bunch of ‘extra’ variables to save on compute is a simple way to optimize. Meanwhile having it internally handle…

[image] chakravala: or if you really want @pure you can just locally define a new method for that like I described here Wasn’t there some warning against @pure functions using non-@pure functions?

[image] oschulz: Wasn’t there some warning against @pure functions using non- @pure functions? No, but @pure is not very well documented and can cause your program to segfault, so only use it if you are extremely confident that you fully understand what you are doing with it. Also, it is not…

[image] oschulz: But with more lightweight functions, e.g. used several times in a (not too long) mathematical expression, manual re-use of results can make the code less readable, as it increases the difference between the code and the “natural” representation. It would be interesting to see…

[image] chakravala: if you are extremely confident that you fully understand what you are doing with it. Cf Bug in doc system? And question on "pure" [in docs]; meaning Julia 1.0 is close? - #5 by mbauman

[image] Tamas_Papp: To make this concrete, consider the e−12(X−μ)TΣ−1(X−μ) That’s a good example - I would often prefer the “textbook” mathematical form in the code in such cases - having the code closer to the math helps readability, in my opinion. I don’t see why this would be more readable…

[image] oschulz: I would rewrite this completely to also avoid the creation of short-lived temporary arrays (esp. if Σ\Sigma is smallish). In practical code I would try to work with (ie store) the Cholesky decomposition \Sigma = LL^T, eg exp(0.5 * sum(abs2, L \ (x .- mu))) I think that most…

In practical code I would try to work with (ie store) the Cholesky decomposition Yes, obviously, in this specific case. I think that most “textbook” formulas facilitate proof techniques … So preserving them in code is not always a good choice Certainly - not always. An you’re right, in cases …

[image] chakravala: No, but @pure is not very well documented I wouldn’t call this “not very well documented” https://docs.julialang.org/en/latest/base/base/#Base.@pure : @pure gives the compiler a hint for the definition of a pure function, helping for type inference. A pure function can …

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Tamas_Papp September 16, 2019, 11:29am 69

Cf Bug in doc system? And question on "pure" [in docs]; meaning Julia 1.0 is close? - #5 by mbauman

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