# Mmap error on windows

**URL:** <https://discourse.julialang.org/t/mmap-error-on-windows/24594>\
**Category:** General Usage\
**Created:** [May 25, 2019, 3:35am UTC](https://discourse.julialang.org/t/mmap-error-on-windows/24594 "2019-05-25T03:35:56Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![ranjan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ranjan/32/4832_2.png) [@ranjan](https://discourse.julialang.org/u/ranjan)\
**Post date:** [May 25, 2019, 3:35am UTC](https://discourse.julialang.org/t/mmap-error-on-windows/24594/1 "2019-05-25T03:35:56Z")

</div>

Hello,

I am using SharedArrays to accumulate matrices that have been generated by different worker processes in my package Circuitscape. However, on windows, when I run the tests, I get:

```julia
Got exception outside of a @test
  could not create mapping view: The operation completed successfully.
  Stacktrace:
   [1] error(::String) at .\error.jl:33
   [2] #mmap#1(::Bool, ::Bool, ::Function, ::Mmap.Anonymous, ::Type{Array{Float64,2}}, ::Tuple{Int64,Int64}, ::Int64) at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\Mmap\src\Mmap.jl:221
   [3] mmap(::Mmap.Anonymous, ::Type{Array{Float64,2}}, ::Tuple{Int64,Int64}, ::Int64) at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\Mmap\src\Mmap.jl:186
   [4] _shm_mmap_array(::Type, ::Tuple{Int64,Int64}, ::String, ::UInt16) at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\SharedArrays\src\SharedArrays.jl:660
   [5] shm_mmap_array(::Type, ::Tuple{Int64,Int64}, ::String, ::UInt16) at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\SharedArrays\src\SharedArrays.jl:639
   [6] #call#3(::Bool, ::Array{Int64,1}, ::Type{SharedArrays.SharedArray{Float64,2}}, ::Tuple{Int64,Int64}) at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\SharedArrays\src\SharedArrays.jl:118
   [7] Type at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\SharedArrays\src\SharedArrays.jl:105 [inlined]
   [8] SharedArrays.SharedArray(::Array{Float64,2}) at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\SharedArrays\src\SharedArrays.jl:347
   [9] initialize_cum_maps(::Array{Float64,2}, ::Bool) at C:\Users\ranjan\.julia\dev\Circuitscape\src\utils.jl:216
   [10] compute_graph_data_no_polygons(::Circuitscape.RasData{Float64,Int32}, ::Circuitscape.RasterFlags) at C:\Users\ranjan\.julia\dev\Circuitscape\src\raster\pairwise.jl:226
   [11] _pt_file_no_polygons_path(::Circuitscape.RasData{Float64,Int32}, ::Circuitscape.RasterFlags, ::Dict{String,String}) at C:\Users\ranjan\.julia\dev\Circuitscape\src\raster\pairwise.jl:60
   [12] raster_pairwise(::Type, ::Type, ::Dict{String,String}) at C:\Users\ranjan\.julia\dev\Circuitscape\src\raster\pairwise.jl:29
   [13] _compute(::Type, ::Type, ::Dict{String,String}) at C:\Users\ranjan\.julia\dev\Circuitscape\src\run.jl:42
   [14] compute_cholmod(::String, ::Int64) at C:\Users\ranjan\.julia\dev\Circuitscape\src\utils.jl:84
   [15] compute_cholmod at C:\Users\ranjan\.julia\dev\Circuitscape\src\utils.jl:75 [inlined]
   [16] macro expansion at .\logging.jl:311 [inlined]
   [17] macro expansion at C:\Users\ranjan\.julia\dev\Circuitscape\src\utils.jl:263 [inlined]
   [18] macro expansion at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\Test\src\Test.jl:1083 [inlined]
   [19] macro expansion at C:\Users\ranjan\.julia\dev\Circuitscape\src\utils.jl:262 [inlined]
   [20] macro expansion at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\Test\src\Test.jl:1083 [inlined]
   [21] runtests(::typeof(compute_cholmod)) at C:\Users\ranjan\.julia\dev\Circuitscape\src\utils.jl:260
   [22] top-level scope at C:\Users\ranjan\.julia\dev\Circuitscape\test\runtests.jl:12 [inlined]
   [23] top-level scope at .\none:0
   [24] include at .\boot.jl:317 [inlined]
   [25] include_relative(::Module, ::String) at .\loading.jl:1044
   [26] include(::Module, ::String) at .\sysimg.jl:29
   [27] include(::String) at .\client.jl:392
   [28] top-level scope at none:0
   [29] eval(::Module, ::Any) at .\boot.jl:319
   [30] macro expansion at .\logging.jl:317 [inlined]
   [31] exec_options(::Base.JLOptions) at .\client.jl:219
   [32] _start() at .\client.jl:425

```

Any ideas on how to debug this? I don’t have an MWE, the easiest way to reproduce is to run `Pkg.test("Circuitscape")` on Windows. There’s an issue filed [here](https://github.com/Circuitscape/Circuitscape.jl/issues/178)

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<div class="post-metadata">

**Author:** ![vlandau](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/vlandau/32/8986_2.png) [@vlandau](https://discourse.julialang.org/u/vlandau)\
**Post date:** [July 10, 2019, 4:43pm UTC](https://discourse.julialang.org/t/mmap-error-on-windows/24594/2 "2019-07-10T16:43:57Z")

</div>

Bumping the above.

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<div class="post-metadata">

**Author:** ![shipengcheng1230](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/shipengcheng1230/32/4089_2.png) [@shipengcheng1230](https://discourse.julialang.org/u/shipengcheng1230)\
**Post date:** [August 3, 2019, 5:55am UTC](https://discourse.julialang.org/t/mmap-error-on-windows/24594/3 "2019-08-03T05:55:25Z")

</div>

Had the same issue in Windows. My guess it’s probably related to initializing a `SharedArray`. Also, in my case, this problem is not reproducible every time, roughly 50/50.

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<div class="post-metadata">

**Author:** ![jmcastro2109](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jmcastro2109/32/38427_2.png) [@jmcastro2109](https://discourse.julialang.org/u/jmcastro2109)\
**Post date:** [November 27, 2019, 2:43pm UTC](https://discourse.julialang.org/t/mmap-error-on-windows/24594/4 "2019-11-27T14:43:15Z")

</div>

Bumping this! Do we have a solution for this issue?

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<div class="post-metadata">

**Author:** ![ranjan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ranjan/32/4832_2.png) [@ranjan](https://discourse.julialang.org/u/ranjan)\
**Post date:** [November 30, 2019, 6:37pm UTC](https://discourse.julialang.org/t/mmap-error-on-windows/24594/5 "2019-11-30T18:37:06Z")

</div>

We don’t have a solution to this particular issue per se but we can avoid it when we move Circuitscape to use mulit-threading.

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<div class="post-metadata">

**Author:** ![mfariacastro](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mfariacastro/32/4432_2.png) [@mfariacastro](https://discourse.julialang.org/u/mfariacastro)\
**Post date:** [August 12, 2020, 10:46pm UTC](https://discourse.julialang.org/t/mmap-error-on-windows/24594/6 "2020-08-12T22:46:49Z")

</div>

Just came here to say that I get this problem quite often on Julia 1.5.0 Windows, when using SharedArrays.