# Can this be written even faster? (CPU)

**URL:** <https://discourse.julialang.org/t/can-this-be-written-even-faster-cpu/109924>\
**Category:** Performance\
**Created:** [February 8, 2024, 12:05pm UTC](https://discourse.julialang.org/t/can-this-be-written-even-faster-cpu/109924 "2024-02-08T12:05:21Z")\
**Posts on this page:** 1\
**Showing post:** 18

<div class="post-metadata">

**Author:** ![Ahmed\_Salih](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ahmed_salih/32/206579_2.png) [@Ahmed\_Salih](https://discourse.julialang.org/u/Ahmed_Salih)\
**Post date:** [February 8, 2024, 6:17pm UTC](https://discourse.julialang.org/t/can-this-be-written-even-faster-cpu/109924/18 "2024-02-08T18:17:44Z")

</div>

Okay I found the issue! It is something with the inverse of gamma in the power calculation. If I write it directly no issue anymore on Julia 1.10:

```julia
using BenchmarkTools
using StaticArrays
using LoopVectorization

# Generate the needed constants
N = 6000
Cb = inv(Float64(100000))
xᵢⱼᶻ = rand(Float64,N*4)
xᵢⱼ = rand(SVector{3,Float64},N*4)
ρ₀ = Float64(1000)
g = Float64(9.81)
drhopLp = zeros(Float64, length(xᵢⱼ))
drhopLn = zeros(Float64, length(xᵢⱼ))

function loopvectorization_approach(Cb,xᵢⱼᶻ,ρ₀,γ⁻¹,g,drhopLp,drhopLn)
    @tturbo for iter in eachindex(xᵢⱼᶻ)
        # IF I COMMENT '* -xᵢⱼᶻ[iter]' NO ALLOCATIONS, WHY?
        Pᵢⱼᴴ = ρ₀ * (-g) * -xᵢⱼᶻ[iter]
        ρᵢⱼᴴ = ρ₀ * ( ^( 1 + (Pᵢⱼᴴ * Cb), 0.14285714285714285) - 1)  
        Pⱼᵢᴴ = -Pᵢⱼᴴ
        ρⱼᵢᴴ = ρ₀ * ( ^( 1 + (Pⱼᵢᴴ * Cb), 0.14285714285714285) - 1)
        
        drhopLp[iter] = ρᵢⱼᴴ
        drhopLn[iter] = ρⱼᵢᴴ
    end
end

l = @benchmark loopvectorization_approach($Cb,$xᵢⱼᶻ,$ρ₀,$γ⁻¹,$g,$drhopLp,$drhopLn)

display(l)

julia> l = @benchmark loopvectorization_approach($Cb,$xᵢⱼᶻ,$ρ₀,$γ⁻¹,$g,$drhopLp,$drhopLn)
BenchmarkTools.Trial: 10000 samples with 1 evaluation.
 Range (min … max): 339.900 μs … 4.994 ms ┊ GC (min … max): 0.00% … 0.00%
 Time (median): 358.600 μs ┊ GC (median): 0.00%
 Time (mean ± σ): 382.900 μs ± 97.110 μs ┊ GC (mean ± σ): 0.00% ± 0.00%

   ▅█▇▅▄▃▂▂▁▁▁▁▁ ▁▁▁▁ ▂
  █████████████████▇▇█▇█████████▇█▇▇▇▇▇▆▄▆▅▆▆▆▅▅▆▄▆▅▁▅▅▅▄▄▆▆▇▇ █
  340 μs Histogram: log(frequency) by time 718 μs <

 Memory estimate: 0 bytes, allocs estimate: 0.

```

Now on to see if I can trick it and use the variable.

EDIT: Both ways are Float64 values, I am confused 😅

Kind regards

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