# How can i improve the performance of the code?

**URL:** <https://discourse.julialang.org/t/how-can-i-improve-the-performance-of-the-code/96622>\
**Category:** Performance\
**Tags:** question, performance\
**Created:** [March 26, 2023, 9:00am UTC](https://discourse.julialang.org/t/how-can-i-improve-the-performance-of-the-code/96622 "2023-03-26T09:00:12Z")\
**Posts on this page:** 10\
**Page:** 1

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**Author:** ![manu\_han](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/manu_han/32/47520_2.png) [@manu\_han](https://discourse.julialang.org/u/manu_han)\
**Post date:** [March 26, 2023, 9:00am UTC](https://discourse.julialang.org/t/how-can-i-improve-the-performance-of-the-code/96622/1 "2023-03-26T09:00:12Z")

</div>

I’m a newbie of julia, and I want to improve the performance of the code included massive iteration and calculation.

[I](https://docs.julialang.org/en/v1/manual/performance-tips/#Avoid-untyped-global-variables)  
Even I red the manual, but I have no ability to adapt all of the solutions…

Here is simplified code.

```julia
using DelimitedFiles
using Plots

global main=readdlm("main.txt"); 
global main=reshape(main,150,27,55) 

function Iteration()
#Temporary parameter
Pres=760; T1=500; T2=500; T3=5000;
    experiment=readdlm("experiment.txt")
    experiment=ifelse.(isnan.(experiment), 0, experiment)
    main_raw=experiment[:,1]; I_raw=experiment[:,2];
    main_start=findmin(main_raw); main_end=findmax(main_raw); 
    main_start=main_start[1]; main_end=main_end[1]
    if main_start<300; main_start=300; end
    if main_end>1200; main_end=1200; end
    main_div=trunc(Int,(100*(main_end-main_start)))

#call parameters
    para_A2C=readdlm("para_A2C.txt");
    a1=para_A2C[:,1]; Ya1=para_A2C[:,2]; Ba1=para_A2C[:,3]; Da1=para_A2C[:,4]; wa1=para_A2C[:,5]; wb1=para_A2C[:,6]; wc1=para_A2C[:,7]; Ea1=para_A2C[:,8]; JG1=para_A2C[:,9]; DAN1=para_A2C[:,10]; 
    para_A2B=readdlm("para_A2B.txt");
    a2=para_A2B[:,1]; Ya2=para_A2B[:,2]; Ba2=para_A2B[:,3]; Da2=para_A2B[:,4]; wa2=para_A2B[:,5]; wb2=para_A2B[:,6]; wc2=para_A2B[:,7]; Ea2=para_A2B[:,8]; JG2=para_A2B[:,9]; DAN2=para_A2B[:,10];
    CAR=readdlm("CAR.txt"); 
    Re=readdlm("Re.txt"); 
    MainCar=readdlm("MainCar.txt");

    main_div=1000; #temporary
#### sub-coefficient calculation ####
Rv=Array{Float64,2}(undef,5,11);
Gv=Array{Float64,2}(undef,5,11);
I_sharp=Array{Float64,2}(undef,150,27);
I_broad=Array{Float64,1}(undef,main_div);

        for A_2C=1:1:5;  
            for A_2B=1:1:11; 
                Rv[A_2C,A_2B]=(wa1[A_2C]*(a1[A_2C]+0.5)-wb1[A_2C]*(a1[A_2C]+0.5)^2+wc1[A_2C]*(a1[A_2C]+0.5)^3)-(wa2[A_2B]*(a2[A_2B]+0.5)-wb2[A_2B]*(a2[A_2B]+0.5)^2+wc2[A_2B]*(a2[A_2B]+0.5)^3); 
                Gv[A_2C,A_2B]=wa1[A_2C]*(a1[A_2C]+0.5)-wb1[A_2C]*(a1[A_2C]+0.5)^2+((a1[A_2C]+0.5)^3);
            end
        end

        main_start=390; main_end=400; main_div=1000; #temporary
        main_shift=zeros(55); #temporary
        main_cal=LinRange(main_start,main_end,main_div); k=1:1:main_div

# 'crazy bottle neck'!!!
            for A_2C=1:1:5 #A_2C 5 
                for A_2B=1:1:5 #A_2B 11
                    numb_v=(A_2B+11*(A_2C-1))
                    for branch=1:1:27
                        for J1=1:1:150 # 150
                            I_sharp[J1,branch]= Re[A_2C,A_2B]^2+*(1/(main[J1,branch,numb_v].-main_shift[numb_v])^4)*CAR[A_2C,A_2B]*MainCar[J1*exp(-1/T2)
                            I_broad[k]=I_broad[k]+I_sharp[J1,branch].*exp.(-1*(main_cal[k].-(main[J1,branch,numb_v].-main_shift[numb_v])))
                        end
                    end
                end
            end
    end

```

In particular, most of the time is spent in the section where the ‘crazy bottle neck’ i denoted. (4 times for)  
Please share your experiences and/or good paper (materials).

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<div class="post-metadata">

**Author:** ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Post date:** [March 26, 2023, 9:17am UTC](https://discourse.julialang.org/t/how-can-i-improve-the-performance-of-the-code/96622/2 "2023-03-26T09:17:56Z")

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Please read; [Performance Tips · The Julia Language](https://docs.julialang.org/en/v1/manual/performance-tips/)

First thing is NOT to use global variables. Define them as **const** or - better - pass them as variables to your function.

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**Author:** ![jmair](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jmair/32/35117_2.png) [@jmair](https://discourse.julialang.org/u/jmair)\
**Post date:** [March 26, 2023, 9:47am UTC](https://discourse.julialang.org/t/how-can-i-improve-the-performance-of-the-code/96622/3 "2023-03-26T09:47:34Z")

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As @ufechner7 mentioned, the main issue with this code is use of the global variable `main`. Easiest way to fix this is to pass it in as an argument to the function.

```julia
function Iteration(main)
    #.... Your code
end

```

And then call it

```julia
main=readdlm("main.txt"); 
main=reshape(main,150,27,55)
Iteration(main)

```

You can add an `@inbounds` to the outermost `for` loop to turn of bounds checking to speed up the code. I would only recommend this once you are sure the code works as it won’t error if you do something unsafe.

There are packages like `LoopVectorization.jl` which provide macros to try and speed up loops too that might be worth checking out.

There are likely other issues but the biggest problem is the global variable.

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<div class="post-metadata">

**Author:** ![sgaure](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sgaure/32/14779_2.png) [@sgaure](https://discourse.julialang.org/u/sgaure)\
**Post date:** [March 26, 2023, 10:07am UTC](https://discourse.julialang.org/t/how-can-i-improve-the-performance-of-the-code/96622/4 "2023-03-26T10:07:04Z")

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The reason global variables are bad for performance is that compilation is done on a function basis. When your `Iteration` function is compiled, the compiler assumes the global variable `main` can change its type at any time. So in your case, every time `main` is accessed in the inner loop, a check is done to find the type of the variable, and the right way to index it is looked up. This kills performance very efficiently in your otherwise quite clean loop.

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<div class="post-metadata">

**Author:** ![manu\_han](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/manu_han/32/47520_2.png) [@manu\_han](https://discourse.julialang.org/u/manu_han)\
**Post date:** [March 26, 2023, 12:41pm UTC](https://discourse.julialang.org/t/how-can-i-improve-the-performance-of-the-code/96622/5 "2023-03-26T12:41:05Z")

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I included the variables ‘main’ in the function Iteration(), before. And compare to before, it (the code I uploaded) improve the speed about 20 %.  
Could you give me an example?

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<div class="post-metadata">

**Author:** ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Post date:** [March 26, 2023, 12:52pm UTC](https://discourse.julialang.org/t/how-can-i-improve-the-performance-of-the-code/96622/6 "2023-03-26T12:52:32Z")

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Can you share the file main.txt ? Then we could play a bit with your code to try to reproduce your issue.

---

<div class="post-metadata">

**Author:** ![manu\_han](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/manu_han/32/47520_2.png) [@manu\_han](https://discourse.julialang.org/u/manu_han)\
**Post date:** [March 28, 2023, 6:46am UTC](https://discourse.julialang.org/t/how-can-i-improve-the-performance-of-the-code/96622/7 "2023-03-28T06:46:06Z")

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Sorry to late reply. I could not find the way to upload the text file. however, it would be not different with rand(222750) in point of programming view. Over 5 million allocation is occuring in my code, and 4 millions are occured in ‘Crzay bottle neck’.  
In addition, I have another question. Idealized code shows low allocation (close to 0)?

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<div class="post-metadata">

**Author:** ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Post date:** [March 28, 2023, 7:46am UTC](https://discourse.julialang.org/t/how-can-i-improve-the-performance-of-the-code/96622/9 "2023-03-28T07:46:02Z")

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> [@manu\_han](#):
>
> Idealized code shows low allocation (close to 0)?

Zero allocations are usually hard to achieve and only in rare cases worth the effort, but reducing allocations by a factor of 5 to 10 is often not too hard by pre-allocating arrays and using views, in-place operators and in-place functions.

---

<div class="post-metadata">

**Author:** ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)\
**Post date:** [March 28, 2023, 7:48am UTC](https://discourse.julialang.org/t/how-can-i-improve-the-performance-of-the-code/96622/10 "2023-03-28T07:48:45Z")

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> [@manu\_han](#):
>
> I could not find the way to upload the text file.

Did you try to compress it first and than upload it to gist: [https://gist.github.com](https://gist.github.com) ?  
Docu: [Creating gists - GitHub Docs](https://docs.github.com/en/get-started/writing-on-github/editing-and-sharing-content-with-gists/creating-gists)

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<div class="post-metadata">

**Author:** ![manu\_han](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/manu_han/32/47520_2.png) [@manu\_han](https://discourse.julialang.org/u/manu_han)\
**Post date:** [March 28, 2023, 10:17am UTC](https://discourse.julialang.org/t/how-can-i-improve-the-performance-of-the-code/96622/11 "2023-03-28T10:17:51Z")

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I should pre-allocating array and using view, maybe.  
The link is follows:

> <https://gist.github.com/Manu-han/9dc01ac03dd5de35edc5ecdbca6b899b>

Is it work?