# Help with increasing performance in badly coded functions

**URL:** <https://discourse.julialang.org/t/help-with-increasing-performance-in-badly-coded-functions/81918>\
**Category:** Performance\
**Created:** [May 30, 2022, 2:50pm UTC](https://discourse.julialang.org/t/help-with-increasing-performance-in-badly-coded-functions/81918 "2022-05-30T14:50:51Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![mauri5566](https://avatars.discourse-cdn.com/v4/letter/m/e99b99/32.png) [@mauri5566](https://discourse.julialang.org/u/mauri5566)\
**Post date:** [May 30, 2022, 2:50pm UTC](https://discourse.julialang.org/t/help-with-increasing-performance-in-badly-coded-functions/81918/1 "2022-05-30T14:50:51Z")

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Hi guys, I need a little help with optimising the performance of a few functions. If you need a more detailed access to my project here’s a notebook ([Largrids.jl/largrid.ipynb at main · adelloste/Largrids.jl · GitHub](https://github.com/adelloste/LinearAlgebraicRepresentation.jl/blob/main/notebooks/largrid.ipynb)) that contains all the functions with inputs ready to be tested with a @btime macro. Here they are.

**cart\_opt** executes the cartesian product of a certain number of arguments:

```julia
function cart_opt(args)::Vector{Tuple}
    return sort(vcat(collect(Iterators.product(args...))...))
end

```

This is the output:

```julia
cart_opt([[1,2],["a"],[3,4]])
4-element Vector{Tuple}:
 (1, "a", 3)
 (1, "a", 4)
 (2, "a", 3)
 (2, "a", 4)

```

This one ( **index2addr\_opt** ) I’m not quite sure what it does but if you have any suggestions I’ll happily take them.

```julia
@inline function index2addr_opt( shape::Vector{Int64} )
    n = length(shape)
    theShape = push!(shape[2:end],1)
    weights = [prod(theShape[k:end]) for k in (1:n)]

    function index2addr0_opt( multiIndex::Vector{Int} )::Int
        return dot(collect(multiIndex), weights) + 1
    end

    return index2addr0_opt
end

```

Here’s the output:

```julia
index2addr_opt([2,7])([1,4])

12

```

My project is about solid modeling, **larCellProd\_opt** is a bit of a mess and it executes the product between two larCells

```julia
@inline function larCellProd_opt(cellLists::Vector{Lar.Cells})::Lar.Cells
    shapes = [length(item) for item in cellLists]
    subscripts = cart_opt([collect(range(0, length=shape)) for shape in shapes])
    indices = [collect(tuple) .+ 1 for tuple in subscripts]
 
    jointCells = [cart_opt([cells[k] for (k,cells) in zip(index,cellLists)]) for index in indices]
    convertIt = index2addr_opt([(length(cellLists[k][1]) > 1) ? shape .+ 1 : shape for (k,shape) in enumerate(shapes) ])
    [map(convertIt, map(collect,jointCells[j])) for j in 1:length(jointCells)]
end

```

Here’s the output:

```julia
c1 = [[0,1],[1,2],[2,3]]
c0 = [[0],[1],[2]]
@btime larCellProd_opt([c1, c1, c0])

27-element Vector{Vector{Int64}}:
 [1, 4, 13, 16]
 [2, 5, 14, 17]
 [3, 6, 15, 18]
 [4, 7, 16, 19]
 [5, 8, 17, 20]
 [6, 9, 18, 21]
 [7, 10, 19, 22]
 [8, 11, 20, 23]
 [9, 12, 21, 24]
 [13, 16, 25, 28]
 [14, 17, 26, 29]
 [15, 18, 27, 30]
 [16, 19, 28, 31]
 ⋮
 [19, 22, 31, 34]
 [20, 23, 32, 35]
 [21, 24, 33, 36]
 [25, 28, 37, 40]
 [26, 29, 38, 41]
 [27, 30, 39, 42]
 [28, 31, 40, 43]
 [29, 32, 41, 44]
 [30, 33, 42, 45]
 [31, 34, 43, 46]
 [32, 35, 44, 47]
 [33, 36, 45, 48]

```

The last function I’d need help with is **createCells** , I’ve been told that **push!** isn’t really good for performance.

```julia
@inline function createCells(V,cells1,W,cells2,vertices)
    cells = []
    for c1 in cells1
        for c2 in cells2
            cell = []
            @inbounds for vc in c1
                @inbounds @simd for wc in c2
                    push!(cell, vertices[[V[:,vc];W[:,wc]]] )
                end
            end
            push!(cells, cell)
        end
    end
    return cells
end

```

---

<div class="post-metadata">

**Author:** ![Oscar\_Smith](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/oscar_smith/32/25343_2.png) [@Oscar\_Smith](https://discourse.julialang.org/u/Oscar_Smith)\
**Post date:** [May 30, 2022, 2:53pm UTC](https://discourse.julialang.org/t/help-with-increasing-performance-in-badly-coded-functions/81918/2 "2022-05-30T14:53:41Z")

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in general, it isn’t worth parallelizing bad code. adding threads will give you a maximum 100x speedup (on a fairly large server), and it’s usually harder than making bad code 100x faster single threaded. step 1 is removing unnecessary allocations.

---

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**Author:** ![DNF](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/dnf/32/10191_2.png) [@DNF](https://discourse.julialang.org/u/DNF)\
**Post date:** [May 30, 2022, 3:25pm UTC](https://discourse.julialang.org/t/help-with-increasing-performance-in-badly-coded-functions/81918/3 "2022-05-30T15:25:16Z")

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> [@mauri5566](#):
>
> ```julia
> function cart_opt(args)::Vector{Tuple}
> return sort(vcat(collect(Iterators.product(args...))...))
> end
> 
> ```

Splatting is bad and `collect` is bad. But first of all get rid of the output type annotation. You are forcing your vector to have an abstract eltype.

Annotating functions with output types is normally not a good idea.

---

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**Author:** ![DNF](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/dnf/32/10191_2.png) [@DNF](https://discourse.julialang.org/u/DNF)\
**Post date:** [May 30, 2022, 3:41pm UTC](https://discourse.julialang.org/t/help-with-increasing-performance-in-badly-coded-functions/81918/4 "2022-05-30T15:41:44Z")

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A good next step is to get rid of every single instance of `collect` in all your functions. See if anything breaks. Check for ways to fix it without using `collect`.

Also, `cell = []` is a red flag for performance. Try to use typed containers, preferably by letting the compiler figure out the types. But a plain `[]` forces the eltype to be `Any`, which hurts performance.

BTW, what is `Lar.Cells`? It looks like the code is using regular Arrays of Arrays.

---

<div class="post-metadata">

**Author:** ![mauri5566](https://avatars.discourse-cdn.com/v4/letter/m/e99b99/32.png) [@mauri5566](https://discourse.julialang.org/u/mauri5566)\
**Post date:** [May 31, 2022, 6:24pm UTC](https://discourse.julialang.org/t/help-with-increasing-performance-in-badly-coded-functions/81918/5 "2022-05-31T18:24:29Z")

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Woud you have any suggestion on how to improve the code?

---

<div class="post-metadata">

**Author:** ![mauri5566](https://avatars.discourse-cdn.com/v4/letter/m/e99b99/32.png) [@mauri5566](https://discourse.julialang.org/u/mauri5566)\
**Post date:** [May 31, 2022, 6:27pm UTC](https://discourse.julialang.org/t/help-with-increasing-performance-in-badly-coded-functions/81918/6 "2022-05-31T18:27:18Z")

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Lar.cell is a type coming from the LinearAlgebraicRepresentation.jl pkg. It’s used to define cells in solid modeling. Btw you were very helpful thx a lot, I will try.