# Why do I get consistently worse performance running as a script than from REPL?

**URL:** <https://discourse.julialang.org/t/why-do-i-get-consistently-worse-performance-running-as-a-script-than-from-repl/102496>\
**Category:** Performance\
**Created:** [August 4, 2023, 4:19pm UTC](https://discourse.julialang.org/t/why-do-i-get-consistently-worse-performance-running-as-a-script-than-from-repl/102496 "2023-08-04T16:19:19Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![nsajko](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/nsajko/32/221187_2.png) [@nsajko](https://discourse.julialang.org/u/nsajko)\
**Post date:** [August 4, 2023, 4:19pm UTC](https://discourse.julialang.org/t/why-do-i-get-consistently-worse-performance-running-as-a-script-than-from-repl/102496/1 "2023-08-04T16:19:19Z")

</div>

`julia_ma_dot_bench.jl`:

```julia
using LinearAlgebra, BenchmarkTools
import MutableArithmetics
const MA = MutableArithmetics;
setprecision(128);
sleep(2)
@btime MA.buffered_operate_to!(b, o, dot, x, y) setup=(o=BigFloat(); n=50; x=rand(BigFloat,n); y=rand(BigFloat,n); b=MA.buffer_for(dot,typeof(x),typeof(y)););

```

Running it as a script (noninteractively):

```julia
$ ./julia /home/nsajko/julia_ma_dot_bench.jl 
  9.418 μs (0 allocations: 0 bytes)
$ ./julia /home/nsajko/julia_ma_dot_bench.jl 
  9.418 μs (0 allocations: 0 bytes)
$ ./julia /home/nsajko/julia_ma_dot_bench.jl 
  9.368 μs (0 allocations: 0 bytes)

```

Running the code by copying to the REPL:

```julia-repl
julia> @btime ...
  8.977 μs (0 allocations: 0 bytes)

julia> @btime ...
  8.830 μs (0 allocations: 0 bytes)

julia> @btime ...
  8.843 μs (0 allocations: 0 bytes)

```

This is on today’s nightly, I don’t know if that matters. Version info:

```julia-repl
julia> versioninfo()
Julia Version 1.11.0-DEV.230
Commit 2c45e3ba9a2 (2023-08-04 00:35 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: 8 × AMD Ryzen 3 5300U with Radeon Graphics
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-15.0.7 (ORCJIT, znver2)
  Threads: 1 on 8 virtual cores

```

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<div class="post-metadata">

**Author:** ![gdalle](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gdalle/32/27854_2.png) [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Post date:** [August 4, 2023, 6:49pm UTC](https://discourse.julialang.org/t/why-do-i-get-consistently-worse-performance-running-as-a-script-than-from-repl/102496/2 "2023-08-04T18:49:40Z")

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What happens if you put several `@btime` in the script?

---

<div class="post-metadata">

**Author:** ![gdalle](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/gdalle/32/27854_2.png) [@gdalle](https://discourse.julialang.org/u/gdalle)\
**Post date:** [August 4, 2023, 7:06pm UTC](https://discourse.julialang.org/t/why-do-i-get-consistently-worse-performance-running-as-a-script-than-from-repl/102496/3 "2023-08-04T19:06:08Z")

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Maybe your `julia` process has a lower process priority than wherever your REPL is running?

---

<div class="post-metadata">

**Author:** ![Palli](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/palli/32/3380_2.png) [@Palli](https://discourse.julialang.org/u/Palli)\
**Post date:** [August 5, 2023, 12:35am UTC](https://discourse.julialang.org/t/why-do-i-get-consistently-worse-performance-running-as-a-script-than-from-repl/102496/4 "2023-08-05T00:35:04Z")

</div>

Could it be that you need to do:

```julia
./julia --startup-file=no julia_ma_dot_bench.jl

```

I don’t know if you have a Julia startup file but it might be doing something different for your REPL session. Also you want to benchmark code without it, and I wish it were not on by default for scripts, but people don’t agree…

I did:

```julia
GC.gc(true) # Note, I think not needed, implied by @btime?

julia> @benchmark MA.buffered_operate_to!(b, o, dot, x, y) setup=(o=BigFloat(); n=50; x=rand(BigFloat,n); y=rand(BigFloat,n); b=MA.buffer_for(dot,typeof(x),typeof(y));)
BenchmarkTools.Trial: 10000 samples with 1 evaluation.
 Range (min … max): 12.903 μs … 67.682 μs ┊ GC (min … max): 0.00% … 0.00%
 Time (median): 13.901 μs ┊ GC (median): 0.00%
 Time (mean ± σ): 14.429 μs ± 2.732 μs ┊ GC (mean ± σ): 0.00% ± 0.00%

```

And with `@btime` I got (which shows median):

```julia
$ julia --startup-file=no julia_ma_dot_bench.jl
  13.133 μs (0 allocations: 0 bytes)

```

I tried to use `@benchmark` from a script but I get no output then… even without the ; to not suppress output (in the REPL).

---

<div class="post-metadata">

**Author:** ![albheim](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/albheim/32/34660_2.png) [@albheim](https://discourse.julialang.org/u/albheim)\
**Post date:** [August 5, 2023, 5:15am UTC](https://discourse.julialang.org/t/why-do-i-get-consistently-worse-performance-running-as-a-script-than-from-repl/102496/5 "2023-08-05T05:15:57Z")

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> [@Palli](#):
>
> And with `@btime` I got (which shows median):

I think `@btime` shows the minimum time, not median, from the docs

> … `@btime` prints the minimum time and memory allocation before returning the value of the expression …

> [@Palli](#):
>
> I tried to use `@benchmark` from a script but I get no output then

The print from `@benchmark` seems to just be the returned object being shown, so maybe if you just wrapped th benchmark in a print it would work in a script as well?