# Sortperm with keyword lt = !isless throws BoundsError
**URL:** https://discourse.julialang.org/t/sortperm-with-keyword-lt-isless-throws-boundserror/92648
**Category:** General Usage
**Created:** [January 7, 2023, 9:37pm UTC](https://discourse.julialang.org/t/sortperm-with-keyword-lt-isless-throws-boundserror/92648 "2023-01-07T21:37:01Z")
**Posts on this page:** 10
**Page:** 1
### Author:  [@rocco\_sprmnt21](https://discourse.julialang.org/u/rocco_sprmnt21)
#### Post date: [January 7, 2023, 9:37pm UTC](https://discourse.julialang.org/t/sortperm-with-keyword-lt-isless-throws-boundserror/92648/1 "2023-01-07T21:37:01Z")
Does this happen to any of you too?
Do you have any idea why?
```julia
sortperm(rand(1:10,10)) # ok
sortperm(rand(1:10,10^2)) # ok
sortperm(rand(1:10,10^7)) # ok
sortperm(rand(1:10,10), lt= >=) #ok
sortperm(rand(1:10,10^2), lt= >=) #ok or sometime crashes language server
sortperm(rand(1:10,10^3), lt= >=) # crashes language server
```
what i get sometimes using Julia directly not in vscode
```julia
_ _ _| |_ __ _ | Type "?" for help, "]?" for Pkg help.
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 1.8.3 (2022-11-14)
_/ |\ __'_|_|_|\__'_| | Official https://julialang.org/ release
|__/ |
julia> sortperm(rand(1:10,10^3), lt= >=)
ERROR: BoundsError: attempt to access 1000-element Vector{Int64} at index [-5]
Stacktrace:
[1] getindex
@ .\array.jl:924 [inlined]
[2] partition!(v::Vector{Int64}, lo::Int64, hi::Int64, o::Base.Order.Perm{Base.Order.Lt{Base.Order.var"#1#3"{typeof(>=), typeof(identity)}}, Vector{Int64}})
@ Base.Sort .\sort.jl:561
[3] sort!(v::Vector{Int64}, lo::Int64, hi::Int64, a::Base.Sort.QuickSortAlg, o::Base.Order.Perm{Base.Order.Lt{Base.Order.var"#1#3"{typeof(>=), typeof(identity)}}, Vector{Int64}})
@ Base.Sort .\sort.jl:572
[4] sort!(v::Vector{Int64}, lo::Int64, hi::Int64, a::Base.Sort.QuickSortAlg, o::Base.Order.Perm{Base.Order.Lt{Base.Order.var"#1#3"{typeof(>=), typeof(identity)}}, Vector{Int64}}) (repeats 2 times)
@ Base.Sort .\sort.jl:577
[5] sort!(v::Vector{Int64}, alg::Base.Sort.QuickSortAlg, order::Base.Order.Perm{Base.Order.Lt{Base.Order.var"#1#3"{typeof(>=), typeof(identity)}}, Vector{Int64}})
@ Base.Sort .\sort.jl:661
[6] sortperm(v::Vector{Int64}; alg::Base.Sort.QuickSortAlg, lt::Function, by::Function, rev::Nothing, order::Base.Order.ForwardOrdering)
@ Base.Sort .\sort.jl:927
[7] top-level scope
@ REPL[1]:1
julia>
```
---
### Author:  [@stevengj](https://discourse.julialang.org/u/stevengj)
#### Post date: [January 7, 2023, 10:40pm UTC](https://discourse.julialang.org/t/sortperm-with-keyword-lt-isless-throws-boundserror/92648/2 "2023-01-07T22:40:55Z")
> [@rocco\_sprmnt21](#):
>
> `sortperm(rand(1:10,10^3), lt= >=) # crashes language server`
I can reproduce.
Interestingly, this seems to crash every Julia version all the way back to Julia 0.4. However, in Julia 0.3 it throws a `BoundsError` exception.
I filed an issue: [sortperm segfaults with lt=(\>=) · Issue #48172 · JuliaLang/julia · GitHub](https://github.com/JuliaLang/julia/issues/48172)
---
### Author:  [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)
#### Post date: [January 8, 2023, 12:27am UTC](https://discourse.julialang.org/t/sortperm-with-keyword-lt-isless-throws-boundserror/92648/3 "2023-01-08T00:27:46Z")
No issues with:
```julia
sortperm(rand(1:10,10^3), lt= >=)
```
on Win 11 Julia Version 1.9.0-beta2
---
### Author:  [@rocco\_sprmnt21](https://discourse.julialang.org/u/rocco_sprmnt21)
#### Post date: [January 8, 2023, 5:38am UTC](https://discourse.julialang.org/t/sortperm-with-keyword-lt-isless-throws-boundserror/92648/4 "2023-01-08T05:38:51Z")
try this, also for values grater than 22
```julia
julia> bget22=repeat([1],22);
julia>
julia> sort(bget22, lt=(>=))
ERROR: BoundsError: attempt to access 22-element Vector{Int64} at index [0]
```
---
### Author:  [@uniment](https://discourse.julialang.org/u/uniment)
#### Post date: [January 8, 2023, 5:40am UTC](https://discourse.julialang.org/t/sortperm-with-keyword-lt-isless-throws-boundserror/92648/5 "2023-01-08T05:40:03Z")
> **Julia 1.8.0 - crashes**
>
> ```julia
> julia> versioninfo()
> Julia Version 1.8.0
> Commit 5544a0fab7 (2022-08-17 13:38 UTC)
> Platform Info:
> OS: Windows (x86_64-w64-mingw32)
> CPU: 20 × 12th Gen Intel(R) Core(TM) i9-12900HK
> WORD_SIZE: 64
> LIBM: libopenlibm
> LLVM: libLLVM-13.0.1 (ORCJIT, goldmont)
> Threads: 1 on 20 virtual cores
>
> julia> sortperm(rand(1:10,10^3), lt= >=)
>
> Please submit a bug report with steps to reproduce this fault, and any error messages that follow (in their entirety). Thanks.
> Exception: EXCEPTION_ACCESS_VIOLATION at 0x614cdf98 -- getindex at .\array.jl:924 [inlined]
> lt at .\ordering.jl:123 [inlined]
> partition! at .\sort.jl:555
> in expression starting at REPL[13]:1
> getindex at .\array.jl:924 [inlined]
> lt at .\ordering.jl:123 [inlined]
> partition! at .\sort.jl:555
> sort! at .\sort.jl:571
> sort! at .\sort.jl:579
> sort! at .\sort.jl:660
> unknown function (ip: 00000000614ce334)
> #sortperm#12 at .\sort.jl:926
> sortperm##kw at .\sort.jl:903
> jl_apply at /cygdrive/c/buildbot/worker/package_win64/build/src\julia.h:1838 [inlined]
> do_call at /cygdrive/c/buildbot/worker/package_win64/build/src\interpreter.c:126
> eval_value at /cygdrive/c/buildbot/worker/package_win64/build/src\interpreter.c:215
> eval_stmt_value at /cygdrive/c/buildbot/worker/package_win64/build/src\interpreter.c:166 [inlined]
> eval_body at /cygdrive/c/buildbot/worker/package_win64/build/src\interpreter.c:594
> jl_interpret_toplevel_thunk at /cygdrive/c/buildbot/worker/package_win64/build/src\interpreter.c:750
> jl_toplevel_eval_flex at /cygdrive/c/buildbot/worker/package_win64/build/src\toplevel.c:906
> jl_toplevel_eval_flex at /cygdrive/c/buildbot/worker/package_win64/build/src\toplevel.c:850
> ijl_toplevel_eval at /cygdrive/c/buildbot/worker/package_win64/build/src\toplevel.c:915 [inlined]
> ijl_toplevel_eval_in at /cygdrive/c/buildbot/worker/package_win64/build/src\toplevel.c:965
> eval at .\boot.jl:368 [inlined]
> eval_user_input at C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.8\REPL\src\REPL.jl:151
> repl_backend_loop at C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.8\REPL\src\REPL.jl:247
> start_repl_backend at C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.8\REPL\src\REPL.jl:232
> #run_repl#47 at C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.8\REPL\src\REPL.jl:369
> run_repl at C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.8\REPL\src\REPL.jl:355
> jfptr_run_repl_69828.clone_1 at C:\Users\unime\AppData\Local\Programs\Julia-1.8.0\lib\julia\sys.dll (unknown line)
> #966 at .\client.jl:419
> jfptr_YY.966_58133.clone_1 at C:\Users\unime\AppData\Local\Programs\Julia-1.8.0\lib\julia\sys.dll (unknown line)
> jl_apply at /cygdrive/c/buildbot/worker/package_win64/build/src\julia.h:1838 [inlined]
> jl_f__call_latest at /cygdrive/c/buildbot/worker/package_win64/build/src\builtins.c:774
> #invokelatest#2 at .\essentials.jl:729 [inlined]
> invokelatest at .\essentials.jl:726 [inlined]
> run_main_repl at .\client.jl:404
> exec_options at .\client.jl:318
> _start at .\client.jl:522
> jfptr__start_57488.clone_1 at C:\Users\unime\AppData\Local\Programs\Julia-1.8.0\lib\julia\sys.dll (unknown line)
> jl_apply at /cygdrive/c/buildbot/worker/package_win64/build/src\julia.h:1838 [inlined]
> true_main at /cygdrive/c/buildbot/worker/package_win64/build/src\jlapi.c:575
> jl_repl_entrypoint at /cygdrive/c/buildbot/worker/package_win64/build/src\jlapi.c:719
> mainCRTStartup at /cygdrive/c/buildbot/worker/package_win64/build/cli\loader_exe.c:59
> BaseThreadInitThunk at C:\WINDOWS\System32\KERNEL32.DLL (unknown line)
> RtlUserThreadStart at C:\WINDOWS\SYSTEM32\ntdll.dll (unknown line)
> Allocations: 3406323 (Pool: 3404487; Big: 1836); GC: 4
>
> ```
>
> process killed
> **Julia 1.8.3 - crashes**
>
> ```julia
> julia> sortperm(rand(1:10,10^3), lt= >=)
> ERROR: BoundsError: attempt to access 1000-element Vector{Int64} at index [-5]
> Stacktrace:
> [1] getindex
> @ .\array.jl:924 [inlined]
> [2] partition!(v::Vector{Int64}, lo::Int64, hi::Int64, o::Base.Order.Perm{Base.Order.Lt{Base.Order.var"#1#3"{typeof(>=), typeof(identity)}}, Vector{Int64}})
> @ Base.Sort .\sort.jl:561
> [3] sort!(v::Vector{Int64}, lo::Int64, hi::Int64, a::Base.Sort.QuickSortAlg, o::Base.Order.Perm{Base.Order.Lt{Base.Order.var"#1#3"{typeof(>=), typeof(identity)}}, Vector{Int64}})
> @ Base.Sort .\sort.jl:572
> [4] sort!(v::Vector{Int64}, alg::Base.Sort.QuickSortAlg, order::Base.Order.Perm{Base.Order.Lt{Base.Order.var"#1#3"{typeof(>=), typeof(identity)}}, Vector{Int64}})
> @ Base.Sort .\sort.jl:661
> [5] sortperm(v::Vector{Int64}; alg::Base.Sort.QuickSortAlg, lt::Function, by::Function, rev::Nothing, order::Base.Order.ForwardOrdering)
> @ Base.Sort .\sort.jl:927
> [6] top-level scope
> @ REPL[1]:1
>
> julia> versioninfo()
> Julia Version 1.8.3
> Commit 0434deb161 (2022-11-14 20:14 UTC)
> Platform Info:
> OS: Windows (x86_64-w64-mingw32)
> CPU: 20 × 12th Gen Intel(R) Core(TM) i9-12900HK
> WORD_SIZE: 64
> LIBM: libopenlibm
> LLVM: libLLVM-13.0.1 (ORCJIT, goldmont)
> Threads: 1 on 20 virtual cores
>
> julia> sortperm(rand(1:10,10^3), lt= >=)
>
> Please submit a bug report with steps to reproduce this fault, and any error messages that follow (in their entirety). Thanks.
> Exception: EXCEPTION_ACCESS_VIOLATION at 0x1bba6de0ce8 -- getindex at .\array.jl:924 [inlined]
> lt at .\ordering.jl:123 [inlined]
> partition! at .\sort.jl:556
> in expression starting at REPL[2]:1
> getindex at .\array.jl:924 [inlined]
> lt at .\ordering.jl:123 [inlined]
> partition! at .\sort.jl:556
> sort! at .\sort.jl:572
> sort! at .\sort.jl:580
> sort! at .\sort.jl:661
> unknown function (ip: 000001bba6de1089)
> #sortperm#12 at .\sort.jl:927
> sortperm##kw at .\sort.jl:904
> jl_apply at C:/workdir/src\julia.h:1839 [inlined]
> do_call at C:/workdir/src\interpreter.c:126
> eval_value at C:/workdir/src\interpreter.c:215
> eval_stmt_value at C:/workdir/src\interpreter.c:166 [inlined]
> eval_body at C:/workdir/src\interpreter.c:612
> jl_interpret_toplevel_thunk at C:/workdir/src\interpreter.c:750
> jl_toplevel_eval_flex at C:/workdir/src\toplevel.c:906
> jl_toplevel_eval_flex at C:/workdir/src\toplevel.c:850
> ijl_toplevel_eval at C:/workdir/src\toplevel.c:915 [inlined]
> ijl_toplevel_eval_in at C:/workdir/src\toplevel.c:965
> eval at .\boot.jl:368 [inlined]
> eval_user_input at C:\workdir\usr\share\julia\stdlib\v1.8\REPL\src\REPL.jl:151
> repl_backend_loop at C:\workdir\usr\share\julia\stdlib\v1.8\REPL\src\REPL.jl:247
> start_repl_backend at C:\workdir\usr\share\julia\stdlib\v1.8\REPL\src\REPL.jl:232
> #run_repl#47 at C:\workdir\usr\share\julia\stdlib\v1.8\REPL\src\REPL.jl:369
> run_repl at C:\workdir\usr\share\julia\stdlib\v1.8\REPL\src\REPL.jl:355
> jfptr_run_repl_67122.clone_1 at C:\Users\unime\AppData\Local\Programs\Julia-1.8.3\lib\julia\sys.dll (unknown line)
> #967 at .\client.jl:419
> jfptr_YY.967_56773.clone_1 at C:\Users\unime\AppData\Local\Programs\Julia-1.8.3\lib\julia\sys.dll (unknown line)
> jl_apply at C:/workdir/src\julia.h:1839 [inlined]
> jl_f__call_latest at C:/workdir/src\builtins.c:774
> #invokelatest#2 at .\essentials.jl:729 [inlined]
> invokelatest at .\essentials.jl:726 [inlined]
> run_main_repl at .\client.jl:404
> exec_options at .\client.jl:318
> _start at .\client.jl:522
> jfptr__start_36493.clone_1 at C:\Users\unime\AppData\Local\Programs\Julia-1.8.3\lib\julia\sys.dll (unknown line)
> jl_apply at C:/workdir/src\julia.h:1839 [inlined]
> true_main at C:/workdir/src\jlapi.c:575
> jl_repl_entrypoint at C:/workdir/src\jlapi.c:719
> mainCRTStartup at C:/workdir/cli\loader_exe.c:59
> BaseThreadInitThunk at C:\WINDOWS\System32\KERNEL32.DLL (unknown line)
> RtlUserThreadStart at C:\WINDOWS\SYSTEM32\ntdll.dll (unknown line)
> Allocations: 2574545 (Pool: 2573238; Big: 1307); GC: 3
>
> ```
>
> throws error first time, killed second
Interestingly, with the MWE in issue #48172, I consistently must run it _twice_ to get a crash; the first time throws an error instead.
> **Julia 1.9.0-alpha1 - runs fine**
>
> ```julia
> julia> versioninfo()
> Julia Version 1.9.0-alpha1
> Commit 0540f9d739 (2022-11-15 14:37 UTC)
> Platform Info:
> OS: Windows (x86_64-w64-mingw32)
> CPU: 20 × 12th Gen Intel(R) Core(TM) i9-12900HK
> WORD_SIZE: 64
> LIBM: libopenlibm
> LLVM: libLLVM-14.0.6 (ORCJIT, alderlake)
> Threads: 20 on 20 virtual cores
>
> julia> sortperm(rand(1:10,10^3), lt= >=)
> 1000-element Vector{Int64}:
> 995
> 983
> 982
> 981
> 980
> 965
> 963
> 960
> 955
> 953
> 951
> 932
> 924
> ⋮
> 102
> 95
> 92
> 90
> 80
> 78
> 76
> 67
> 49
> 34
> 27
> 9
>
> julia> a = [10, 9, 8, 9, 7, 1, 3, 10, 4, 5, 5, 4, 6, 10, 10, 2, 2, 2, 8, 9, 1, 2, 8, 6, 7, 10, 1, 3, 5, 10];
>
> julia> sortperm(a, lt=(>=))
> 30-element Vector{Int64}:
> 30
> 26
> 15
> 14
> 8
> 1
> 20
> 4
> 2
> 23
> 19
> 3
> 25
> ⋮
> 10
> 12
> 9
> 28
> 7
> 22
> 18
> 17
> 16
> 27
> 21
> 6
>
> julia> a[sortperm(a, lt=(>=))]
> 30-element Vector{Int64}:
> 10
> 10
> 10
> 10
> 10
> 10
> 9
> 9
> 9
> 8
> 8
> 8
> 7
> ⋮
> 5
> 4
> 4
> 3
> 3
> 2
> 2
> 2
> 2
> 1
> 1
> 1
>
> ```
---
### Author:  [@uniment](https://discourse.julialang.org/u/uniment)
#### Post date: [January 8, 2023, 5:41am UTC](https://discourse.julialang.org/t/sortperm-with-keyword-lt-isless-throws-boundserror/92648/6 "2023-01-08T05:41:18Z")
On Julia 1.9.0-alpha1:
```julia
julia> bget22=repeat([1],22);
julia> sort(bget22, lt=(>=))
22-element Vector{Int64}:
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
julia> bget22=repeat([23],22);
julia> sort(bget22, lt=(>=))
22-element Vector{Int64}:
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
23
```
---
### Author:  [@rocco\_sprmnt21](https://discourse.julialang.org/u/rocco_sprmnt21)
#### Post date: [January 8, 2023, 8:53am UTC](https://discourse.julialang.org/t/sortperm-with-keyword-lt-isless-throws-boundserror/92648/7 "2023-01-08T08:53:51Z")
The problem (or part of it) seems to be in calculating the left end of the pivot for the sort! function.
Is it possible to trace the steps of the calculation via debug in vscode?
how?
---
### Author:  [@aplavin](https://discourse.julialang.org/u/aplavin)
#### Post date: [January 8, 2023, 9:33am UTC](https://discourse.julialang.org/t/sortperm-with-keyword-lt-isless-throws-boundserror/92648/8 "2023-01-08T09:33:31Z")
Silent crash is a bug, but `sort(lt= >=)` isn’t expected to work anyway. Docs say:
> the lt keyword allows providing a custom “less than” function (note that
> for every x and y, only one of lt(x,y) and lt(y,x) can return true
---
### Author:  [@rocco\_sprmnt21](https://discourse.julialang.org/u/rocco_sprmnt21)
#### Post date: [January 8, 2023, 11:20am UTC](https://discourse.julialang.org/t/sortperm-with-keyword-lt-isless-throws-boundserror/92648/9 "2023-01-08T11:20:31Z")
not only crashing silently, but you may end up in a loop that seems to never end
`sort!(rand(1:10, 10^7),lt= >=)`
In any case, it would be preferable to block unmanaged inputs from code.
And, if possible, give reasons for introducing this limitation, which seems artificial in the context of a sorting function.
I also submit this case to tell where this problem came from.
[here](https://discourse.julialang.org/t/index-of-max-values-of-n-columns-in-a-dataframe-without-manually-entering-each-column/92532/15) I wanted to use the sortperm function to sort the values in descending order as requested by the OP.
Instead of rev=true it occurred to me to use the kwarg `lt`, which has by default `isless`. I tried `isgreater` but it wasn’t defined so I thought `!isless` or `(>=)`
---
### Author:  [@Dan](https://discourse.julialang.org/u/Dan)
#### Post date: [January 8, 2023, 12:52pm UTC](https://discourse.julialang.org/t/sortperm-with-keyword-lt-isless-throws-boundserror/92648/10 "2023-01-08T12:52:30Z")
Perhaps, introduce `unsafe_sort` which can take a non-pre-vetted order, and the regular `sort` will work with functions bearing ‘Ordering’ trait?
But writing `unsafe_sort` would be a pain. Checking order is non-reflexive (`lt(x,x)` is false) once before sort, might cost little and do away with many such problem cases.