# Sort on tuple is \> 4x as fast as sortrows on the equivalent array

**URL:** <https://discourse.julialang.org/t/sort-on-tuple-is-4x-as-fast-as-sortrows-on-the-equivalent-array/5861>\
**Category:** General Usage\
**Tags:** performance, sort\
**Created:** [September 13, 2017, 3:57am UTC](https://discourse.julialang.org/t/sort-on-tuple-is-4x-as-fast-as-sortrows-on-the-equivalent-array/5861 "2017-09-13T03:57:47Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![anon94023334](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@anon94023334](https://discourse.julialang.org/u/anon94023334)\
**Post date:** [September 13, 2017, 3:57am UTC](https://discourse.julialang.org/t/sort-on-tuple-is-4x-as-fast-as-sortrows-on-the-equivalent-array/5861/1 "2017-09-13T03:57:47Z")

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I was a little surprised at the performance difference here:

```julia
julia> shuffle!(a)
9-element Array{Tuple{Int64,Int64},1}:
 (1, 2)
 (2, 20)
 (2, 30)
 (2, 10)
 (3, 39)
 (1, 6)
 (1, 4)
 (3, 31)
 (3, 33)

julia> s = [i[1] for i in a]; d = [i[2] for i in a];

julia> b = hcat(s, d)
9×2 Array{Int64,2}:
 1 2
 2 20
 2 30
 2 10
 3 39
 1 6
 1 4
 3 31
 3 33

julia> @benchmark(sort($a))
BenchmarkTools.Trial:
  memory estimate: 384 bytes
  allocs estimate: 3
  --------------
  minimum time: 231.093 ns (0.00% GC)
  median time: 445.286 ns (0.00% GC)
  mean time: 483.968 ns (3.47% GC)
  maximum time: 18.558 μs (0.00% GC)
  --------------
  samples: 10000
  evals/sample: 290

julia> @benchmark(sortrows($b))
BenchmarkTools.Trial:
  memory estimate: 1.22 KiB
  allocs estimate: 18
  --------------
  minimum time: 1.104 μs (0.00% GC)
  median time: 2.005 μs (0.00% GC)
  mean time: 2.303 μs (4.32% GC)
  maximum time: 226.557 μs (93.68% GC)
  --------------
  samples: 10000
  evals/sample: 10

```

---

<div class="post-metadata">

**Author:** ![JackDevine](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jackdevine/32/1048_2.png) [@JackDevine](https://discourse.julialang.org/u/JackDevine)\
**Post date:** [September 13, 2017, 6:54am UTC](https://discourse.julialang.org/t/sort-on-tuple-is-4x-as-fast-as-sortrows-on-the-equivalent-array/5861/2 "2017-09-13T06:54:47Z")

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I think that this is because `sortrows` is optimized for arrays that are bigger than nx2. For example,

```julia
n = 10
m = 10

a = rand(1:10, n, m)
b = [(a[i,:]...) for i in 1:n]

@benchmark sortrows($a)

BenchmarkTools.Trial: 
  memory estimate: 1.92 KiB
  allocs estimate: 19
  --------------
  minimum time: 1.196 μs (0.00% GC)
  median time: 1.340 μs (0.00% GC)
  mean time: 1.557 μs (6.74% GC)
  maximum time: 163.354 μs (93.21% GC)
  --------------
  samples: 10000
  evals/sample: 10

@benchmark sort($b)

BenchmarkTools.Trial: 
  memory estimate: 1.03 KiB
  allocs estimate: 3
  --------------
  minimum time: 467.066 ns (0.00% GC)
  median time: 641.760 ns (0.00% GC)
  mean time: 734.292 ns (9.24% GC)
  maximum time: 18.231 μs (88.09% GC)
  --------------
  samples: 10000
  evals/sample: 198

```

but if I set `m = 1_000`, then I get

```julia
@benchmark sortrows($a)

BenchmarkTools.Trial: 
  memory estimate: 79.25 KiB
  allocs estimate: 20
  --------------
  minimum time: 11.251 μs (0.00% GC)
  median time: 16.116 μs (0.00% GC)
  mean time: 29.179 μs (22.21% GC)
  maximum time: 4.927 ms (93.81% GC)
  --------------
  samples: 10000
  evals/sample: 1

@benchmark sort($b)

BenchmarkTools.Trial: 
  memory estimate: 78.36 KiB
  allocs estimate: 4
  --------------
  minimum time: 51.590 μs (0.00% GC)
  median time: 58.386 μs (0.00% GC)
  mean time: 73.561 μs (8.27% GC)
  maximum time: 3.661 ms (90.14% GC)
  --------------
  samples: 10000
  evals/sample: 1

```

So `sortrows` closes the gap.

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<div class="post-metadata">

**Author:** ![JackDevine](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jackdevine/32/1048_2.png) [@JackDevine](https://discourse.julialang.org/u/JackDevine)\
**Post date:** [September 13, 2017, 7:07am UTC](https://discourse.julialang.org/t/sort-on-tuple-is-4x-as-fast-as-sortrows-on-the-equivalent-array/5861/3 "2017-09-13T07:07:58Z")

</div>

Although, a 4x speed up does seem a little big…