# CMake 3.17 impossibly slow configuring VTK?

**URL:** <https://discourse.vtk.org/t/cmake-3-17-impossibly-slow-configuring-vtk/2955>\
**Category:** Development\
**Created:** [April 3, 2020, 7:26pm UTC](https://discourse.vtk.org/t/cmake-3-17-impossibly-slow-configuring-vtk/2955 "2020-04-03T19:26:12Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![seanm](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/s/a88e4f/32.png) [@seanm](https://discourse.vtk.org/u/seanm)\
**Post date:** [April 3, 2020, 7:26pm UTC](https://discourse.vtk.org/t/cmake-3-17-impossibly-slow-configuring-vtk/2955/1 "2020-04-03T19:26:12Z")

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Hi all,

Is it just me, or is there a major speed regression with the new CMake 3.17? On two different Macs now I’ve been waiting 10s of minutes for the ‘configure’ step. Steps like this:

Looking for frexpl  
Looking for frexpl - found  
Looking for gethostname  
Looking for gethostname - found

take minutes and minutes…

Anyone else?

Sean

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**Author:** ![ben.boeckel](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/b/ea5d25/32.png) [@ben.boeckel](https://discourse.vtk.org/u/ben.boeckel)\
**Post date:** [April 3, 2020, 7:43pm UTC](https://discourse.vtk.org/t/cmake-3-17-impossibly-slow-configuring-vtk/2955/2 "2020-04-03T19:43:04Z")

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Hmm. I haven’t noticed an issue on Linux so far. Looks like something with `try_compile` though. What generator are you using?

@brad.king @RobertMaynard

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**Author:** ![seanm](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/s/a88e4f/32.png) [@seanm](https://discourse.vtk.org/u/seanm)\
**Post date:** [April 3, 2020, 8:10pm UTC](https://discourse.vtk.org/t/cmake-3-17-impossibly-slow-configuring-vtk/2955/3 "2020-04-03T20:10:06Z")

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The default one, unix makefiles. I revert to CMake 3.16.2 and it’s definitely faster.

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**Author:** ![RobertMaynard](https://discourse.vtk.org/user_avatar/discourse.vtk.org/robertmaynard/32/24_2.png) [@RobertMaynard](https://discourse.vtk.org/u/RobertMaynard)\
**Post date:** [April 3, 2020, 8:16pm UTC](https://discourse.vtk.org/t/cmake-3-17-impossibly-slow-configuring-vtk/2955/4 "2020-04-03T20:16:18Z")

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Running from a `macOS 10.13.6` machine

```auto
time ./cmake-3.17/CMake.app/Contents/bin/cmake -S src/ -B build
> 49.78 real 27.95 user 18.73 sys

time ./cmake-3.16/CMake.app/Contents/bin/cmake -S src/ -B build
> 49.00 real 27.50 user 18.84 sys 

```

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<div class="post-metadata">

**Author:** ![seanm](https://discourse.vtk.org/letter_avatar_proxy/v4/letter/s/a88e4f/32.png) [@seanm](https://discourse.vtk.org/u/seanm)\
**Post date:** [April 3, 2020, 8:39pm UTC](https://discourse.vtk.org/t/cmake-3-17-impossibly-slow-configuring-vtk/2955/5 "2020-04-03T20:39:58Z")

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Interesting, it is fast with `cmake`, it seems only insanely slow with `ccmake`. Could you try?

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**Author:** ![RobertMaynard](https://discourse.vtk.org/user_avatar/discourse.vtk.org/robertmaynard/32/24_2.png) [@RobertMaynard](https://discourse.vtk.org/u/RobertMaynard)\
**Post date:** [April 3, 2020, 9:00pm UTC](https://discourse.vtk.org/t/cmake-3-17-impossibly-slow-configuring-vtk/2955/6 "2020-04-03T21:00:39Z")

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I have been able to reproduce and reported this as a CMake regression with a simple demo

[https://gitlab.kitware.com/cmake/cmake/-/issues/20535](https://gitlab.kitware.com/cmake/cmake/-/issues/20535)