Thanks guys. So to clarify: FloatingPoint is not a concrete types, so explicitly defining variables or function inputs using it will not speed things up. Instead, I should use Float64, Float32, etc.
Is Int an abstract type as well? I'm wondering if I should go back and rename everything my_var::Int to my_var::Int32. John: I couldn't find the mutate!() function in the Julia Standard Library v0.3. Do you mean my own function that mutates the source array? On Monday, 25 August 2014 14:54:14 UTC-4, Patrick O'Leary wrote: > > On Monday, August 25, 2014 12:28:00 PM UTC-5, John Myles White wrote: >> >> Array{FloatingPoint} isn't related to Array{Float64}. Julia's type system >> always employs invariance for parametric types: >> https://en.wikipedia.org/wiki/Covariance_and_contravariance_(computer_science) >> >> <https://www.google.com/url?q=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FCovariance_and_contravariance_%28computer_science%29&sa=D&sntz=1&usg=AFQjCNH5Mpuwh71o9dv0_TDx9OcMvvKfWg> >> > > To underline this point a bit, it's even a bit worse than that: > Array{FloatingPoint} will work just fine for a lot of things, but it stores > all elements as heap pointers, so array-like operations (such as linear > algebra routines) will often be extremely slow. > > As a rule, you almost never use an abstract type as the type parameter of > a parametric type for this reason. Where you wish to be generic over a > specific family of types under an abstract type, you can use type > constraints: > > function foo{T<:FloatingPoint}(src::Array{T,1}) > ... > end > > But often type annotations can be omitted completely. >