BUG: Call SetGlobalDefaultNumberOfThreads when processing "-threads"

[N-Dekker]

It appears that SetGlobalMaximumNumberOfThreads may not affect the size of ITK's ThreadPool. The ThreadPool only uses "GlobalDefaultNumberOfThreads".

• Related to ITK issue GlobalDefaultNumberOfThreads should not be greater than GlobalMaximumNumberOfThreads InsightSoftwareConsortium/ITK#4773 "GlobalDefaultNumberOfThreads should not be greater than GlobalMaximumNumberOfThreads"

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@Svdvoort This should at least partially address the multi-threading issues you reported

[N-Dekker]

For the record, on my LKEB/LUMC Windows 10 pc (6 cores, 12 logical processors), I tested the effect of the "-threads" command-line option within Visual Studio 2022, both before and after this pull request:

Before this pull request:

"-threads" command-line option	actual number of threads
no such option	16
"-threads" 0	16
"-threads" 1	16
"-threads" 2	16
"-threads" 4	16

After this pull request:

"-threads" command-line option	actual number of threads
no such option	16
"-threads" 0	5
"-threads" 1	5
"-threads" 2	6
"-threads" 4	8

These eight threads in the last row (from "-threads" 4) are the main thread, three Windows system threads, and four threads maintained by ITK's ThreadPool.

By the way, those three Windows system threads are there because of Windows 10 Parallel Loading: https://blogs.blackberry.com/en/2017/10/windows-10-parallel-loading-breakdown

[N-Dekker]

@mstaring @stefanklein Please check that this is good enough: "-threads" 4 will create an ITK ThreadPool of (at most) 4 threads, but the executable may still have some other threads as well (e.g., a main thread, and a few "system threads".)

[stefanklein]

No strong opinion, sounds reasonable to me Stefan Van: Niels Dekker ***@***.***> Verzonden: vrijdag 12 juli 2024 16:43 Aan: SuperElastix/elastix ***@***.***> CC: Stefan Klein ***@***.***>; Mention ***@***.***> Onderwerp: Re: [SuperElastix/elastix] BUG: Call `SetGlobalDefaultNumberOfThreads` when processing "-threads" (PR #1195) Waarschuwing: Deze e-mail is afkomstig van buiten de organisatie. Klik niet op links en open geen bijlagen, tenzij u de afzender herkent en weet dat de inhoud veilig is. Caution: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. @mstaring<https://github.com/mstaring> @stefanklein<https://github.com/stefanklein> Please check that this is good enough: "-threads" 4 will create an ITK ThreadPool of (at most) 4 threads, but the executable may still have some other threads as well (e.g., a main thread, and a few "system threads".) - Reply to this email directly, view it on GitHub<#1195 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AAF2LNLHUBV7TGNAKGMHMS3ZL7TNPAVCNFSM6AAAAABKW74KJWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDEMRVG42DENBYGY>. You are receiving this because you were mentioned.Message ID: ***@***.******@***.***>>