How to convert the binary form of a float to an integer, and vice versa?

General Usage
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7

I mean it’s only an approximation and if you compare performance:

using BenchmarkTools

function fast_sqrt(y::Float32)
    x2 = y * 0.5f0
    i = reinterpret(Int32, y)
    i = 0x5f3759df - (i >> 1)
    y = reinterpret(Float32, i)
    y = y * (1.5f0 - x2 * y^2)
    return y
end


function compare_inv_sqrt(n=100000)
    arr = abs.(10000 .* randn(Float32, n)) 
    @btime fast_sqrt.($arr)
    @btime 1 ./ sqrt.($arr)
    @btime @fastmath 1 ./ sqrt.($arr)
    return nothing
end

## REPL
julia> compare_inv_sqrt()
  23.092 μs (2 allocations: 390.70 KiB)
  154.720 μs (2 allocations: 390.70 KiB)
  36.811 μs (2 allocations: 390.70 KiB)

Performance is only like ~40% better.