# Why doesn't VTK\_SMP\_IMPLEMENTATION\_TYPE default to STDThread?
**URL:** https://discourse.vtk.org/t/why-doesnt-vtk-smp-implementation-type-default-to-stdthread/8293
**Category:** Development
**Created:** [April 13, 2022, 8:39pm UTC](https://discourse.vtk.org/t/why-doesnt-vtk-smp-implementation-type-default-to-stdthread/8293 "2022-04-13T20:39:52Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@seanm](https://discourse.vtk.org/u/seanm)
#### Post date: [April 13, 2022, 8:39pm UTC](https://discourse.vtk.org/t/why-doesnt-vtk-smp-implementation-type-default-to-stdthread/8293/1 "2022-04-13T20:39:52Z")
Hi all,
Why does VTK\_SMP\_IMPLEMENTATION\_TYPE default to Sequential instead of STDThread?
Are there platforms where STDThread doesn’t exist/work?
Cheers,
Sean
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### Author:  [@will.schroeder](https://discourse.vtk.org/u/will.schroeder)
#### Post date: [April 13, 2022, 8:46pm UTC](https://discourse.vtk.org/t/why-doesnt-vtk-smp-implementation-type-default-to-stdthread/8293/2 "2022-04-13T20:46:53Z")
Good question, but note that std::thread is extremely sensitive to any hint of race conditions. I have also seen it much, much slower than TBB, and even slower than sequential on occasion. I personally never use std::thread except when debugging, and always prefer TBB.
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### Author:  [@ben.boeckel](https://discourse.vtk.org/u/ben.boeckel)
#### Post date: [April 13, 2022, 8:55pm UTC](https://discourse.vtk.org/t/why-doesnt-vtk-smp-implementation-type-default-to-stdthread/8293/3 "2022-04-13T20:55:59Z")
Yes, the deadlocks that were still around in STDThread blocked it from being the default. See `.gitlab/ci/ctest_exclusions.cmake` for the tests that seem to be affected.
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### Author:  [@mwestphal](https://discourse.vtk.org/u/mwestphal)
#### Post date: [April 14, 2022, 7:33am UTC](https://discourse.vtk.org/t/why-doesnt-vtk-smp-implementation-type-default-to-stdthread/8293/4 "2022-04-14T07:33:28Z")
@Charles_Gueunet
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### Author:  [@seanm](https://discourse.vtk.org/u/seanm)
#### Post date: [April 14, 2022, 4:21pm UTC](https://discourse.vtk.org/t/why-doesnt-vtk-smp-implementation-type-default-to-stdthread/8293/5 "2022-04-14T16:21:02Z")
Sounds like a job for Thread Sanitizer!
I should restore my TSan nightly build… I believe I disabled it because it was taking a long time, but perhaps I can build less of VTK to get things going.
I also have a patch coming that fixes at least one TSan complaint…
Sean
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### Author:  [@will.schroeder](https://discourse.vtk.org/u/will.schroeder)
#### Post date: [April 14, 2022, 4:54pm UTC](https://discourse.vtk.org/t/why-doesnt-vtk-smp-implementation-type-default-to-stdthread/8293/6 "2022-04-14T16:54:57Z")
Yes, tsan is extremely useful but as you say slow. It would be good to work through the std::thread issues that Ben referred to.
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### Author:  [@ben.boeckel](https://discourse.vtk.org/u/ben.boeckel)
#### Post date: [April 14, 2022, 4:55pm UTC](https://discourse.vtk.org/t/why-doesnt-vtk-smp-implementation-type-default-to-stdthread/8293/7 "2022-04-14T16:55:21Z")
I have an MR somewhere to re-enable the sanitizers, but the CI is a complete mess and I don’t have time to make it happy enough to turn on.
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### Author:  [@estan](https://discourse.vtk.org/u/estan)
#### Post date: [April 14, 2022, 5:00pm UTC](https://discourse.vtk.org/t/why-doesnt-vtk-smp-implementation-type-default-to-stdthread/8293/8 "2022-04-14T17:00:06Z")
Let me just cheer on from the sidelines to getting std::thread in shape. I guess once it’s mature enough, it could be used for the PyPI wheels? That would be great.