# Contents of the function run well when timed alone, but not when they are in a loop inside the function

**URL:** <https://discourse.julialang.org/t/contents-of-the-function-run-well-when-timed-alone-but-not-when-they-are-in-a-loop-inside-the-function/76886>\
**Category:** Performance\
**Tags:** question, performance, arrays, function, sparse\
**Created:** [February 22, 2022, 7:13am UTC](https://discourse.julialang.org/t/contents-of-the-function-run-well-when-timed-alone-but-not-when-they-are-in-a-loop-inside-the-function/76886 "2022-02-22T07:13:40Z")\
**Posts on this page:** 1\
**Showing post:** 7

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**Author:** ![ayushinav](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ayushinav/32/32687_2.png) [@ayushinav](https://discourse.julialang.org/u/ayushinav)\
**Post date:** [May 28, 2022, 1:49pm UTC](https://discourse.julialang.org/t/contents-of-the-function-run-well-when-timed-alone-but-not-when-they-are-in-a-loop-inside-the-function/76886/7 "2022-05-28T13:49:49Z")

</div>

Hello all, sorry for disturbing you again, looks like I have run into a similar problem again. I hope it’s not the same silly doubt as the last time.  
Let’s define the variables first:

```julia
rickfg= fill(0 .+ im*0., nf, 1, 1, 1, 1, 1) |>gpu; # FFT of ricker
fg= fill(0 .+ im*0., nf, 1, 1,1,1,1)|>gpu; # fgrid
shiftg= fill(0 .+ im*0., 1, nr, nz, ny, nx, 1)|>gpu; # time shifts
Tshiftg= fill(0 .+ im*0., 1,1,1,1,1,nT)|>gpu; #time shits for temporal domain
G_vec_per_rec= fill(0. + im* 0., nf, 1, nz, ny, nx, nT) |>gpu;
G_unvec_per_rec= fill(0. + im* 0., nf, nz*ny*nx*nT) |>gpu;
delay= fill(0. + im.*0, 1, 1, nz, ny, nx, nT) |>gpu;
delay_rf= fill(0. + im* 0., nf, 1, nz, ny, nx, nT) |>gpu;
dunvec= fill(0. + im.*0, nf,nr) |>gpu;
munvec= fill(0. + im.*0, nz*ny*nx*nT, 1) |>gpu;

```

Later on, these are updated with values, to reproduce, you can fill them up with random complex numbers, there is no sparsity in any arrays here, and I am using `Flux.jl` along with `CUDA.jl` to run them on GPU, and took `nr= 125, nz= 61, ny== 1, nx= 61, nf= 401, nT= 141`.

The following line of codes

```julia
@time broadcast!(+, delay, view(shiftg, :, ir:ir, :, :, :, :), Tshiftg);
@time broadcast!(*, delay_rf, -im, 2π, fg, delay);
@time broadcast!(exp, delay_rf, delay_rf);
@time broadcast!(*, G_vec_per_rec, rickfg, delay_rf);
@time copyto!(G_unvec_per_rec, G_vec_per_rec);
@time dd= view(dunvec, :, ir:ir)
# @time # mm= view(munvec, :,ir:ir)
@time mul!(dd, G_unvec_per_rec, munvec);

```

return

```julia
  0.000101 seconds (51 allocations: 1.734 KiB)
  0.000052 seconds (7 allocations: 512 bytes)
  0.000072 seconds (26 allocations: 2.250 KiB)
  0.000058 seconds (7 allocations: 512 bytes)
  0.000053 seconds (2 allocations: 32 bytes)
  0.000011 seconds (5 allocations: 176 bytes)
  0.000139 seconds (17 allocations: 304 bytes)

```

In all, a total of approx. 0.000500 seconds.  
but the following

```julia
for i in 1:10
    @time for ir in 1:nr
        broadcast!(+, delay, view(shiftg, :, ir:ir, :, :, :, :), Tshiftg);
        broadcast!(*, delay_rf, -im, 2π, fg, delay);
        broadcast!(exp, delay_rf, delay_rf);
        broadcast!(*, G_vec_per_rec, rickfg, delay_rf);
        copyto!(G_unvec_per_rec, G_vec_per_rec);
        dd= view(dunvec, :, ir:ir)
        # mm= view(munvec, :,ir:ir)
        mul!(dd, G_unvec_per_rec, munvec);
    end
end

```

returns

```julia
  0.644182 seconds (14.27 k allocations: 678.453 KiB)
  7.918085 seconds (14.27 k allocations: 678.453 KiB)
  7.953713 seconds (14.27 k allocations: 678.453 KiB)
  7.958340 seconds (14.27 k allocations: 678.453 KiB)
  7.879235 seconds (14.27 k allocations: 678.453 KiB)
  7.940350 seconds (14.27 k allocations: 678.453 KiB)
  8.226722 seconds (14.27 k allocations: 678.453 KiB)
  8.210767 seconds (14.27 k allocations: 678.453 KiB)
  8.279914 seconds (14.27 k allocations: 678.453 KiB)
  8.243146 seconds (14.27 k allocations: 678.453 KiB)

```

Things add up for the first runtime, 0.000500\*nr(=125)\*10= 0.625 seconds, but after that it messes up. I don’t think it’s the global variables thing this time, because I’m running them without defining any functions. Am I again missing something basic? Please let me know, and apologies if it’s again a simple thing.  
I’m tagging you all so that you receive the notifications @goerch @Benny@maphdze @FrancisKing  
Thanks for your time!

---

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