[PATCH] D25564: Add interface to compute number of physical cores on host system

[Teresa Johnson via llvm-commits]

On Thu, Oct 13, 2016 at 10:35 AM, Aaron Ballman <aaron.ballman at gmail.com>
wrote:

> On Thu, Oct 13, 2016 at 1:30 PM, Mehdi AMINI <mehdi.amini at apple.com>
> wrote:
> > mehdi_amini added inline comments.
> >
> >
> > ================
> > Comment at: lib/Support/Host.cpp:1239
> > +// On other systems, return -1 to indicate unknown.
> > +int computeHostNumPhysicalCores() { return -1; }
> > +#endif
> > ----------------
> > aaron.ballman wrote:
> >> No Windows implementation? Should be able to use `
> GetLogicalProcessorInformation()` pretty easily.
> >>
> >> https://msdn.microsoft.com/en-us/library/windows/desktop/
> ms683194(v=vs.85).aspx
> > Patch welcome :)
>
> Happy to work on a patch, but I worry when we add new interfaces that
> don't work across platforms unless they bark loudly. An assert() here
> might not be amiss.
>

I don't want to add an assert, because when I submit the follow-on patch
that uses this in a new thread interface it will fall back to
hardware_concurrency if this returns -1. This seems like a friendlier
approach, since for all platforms but the ones implemented here it will
cause the user (ThinLTO backends initially) to fall back to the current
default parallelism. And they will then automatically pick up any support
added for other platforms.


>
> ~Aaron
>
> >
> > I'll supply the MacOS version when possible.
> >
> >
> > https://reviews.llvm.org/D25564
> >
> >
> >
>



-- 
Teresa Johnson |  Software Engineer |  tejohnson at google.com |  408-460-2413
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