[MCLEAN-102] Fast is slower on windows with many cores

**[Delany](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=delany)** opened **[MCLEAN-102](https://issues.apache.org/jira/browse/MCLEAN-102?redirect=false)** and commented

I run a 500+ module project with 4 core Linux and experience a 20sec improvement in reactor build time when enabling the fast.

My one colleagues runs the same build with 4 cores on Windows and also sees an improvement.

But two other colleagues run the same build with 12 cores on Windows (one uses cygwin, the other powershell) and they consistently see a slowdown from 2:14 to 3:23, for example.

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**Affects:** 3.2.0

The report names no source files, tests, or entry points. Start by reproducing the fast-mode comparison on Windows with a 500+ module project and 4 versus 12 cores, using Cygwin and PowerShell as reported. Done means identifying the cause of the slowdown and confirming improved timings without regressing the Linux case.

Written by the indexing model from the issue text.