RE: [apple scitech] posix_memalign on PowerPC?

• Subject: RE: [apple scitech] posix_memalign on PowerPC?
• From: "Kaufman, Ian" <email@hidden>
• Date: Fri, 19 Dec 2008 11:03:09 -0800
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• Delivered-to: email@hidden
• Thread-index: Aclhe9OkNfWwGQymTCmswBBxqKCFMwAj2sxQAAA6XpA=
• Thread-topic: [apple scitech] posix_memalign on PowerPC?

> >
> > > Indeed, we just had to find a replacement for _posix_memalign
> for
> > > MSVC
> > > ... now it looks like we need a replacement here too!
> > >
> > > Please tell me what equivalent function your platform has (hint,
> > on
> > > windows it was called _aligned_malloc).
> >
> > I'm helping a PowerPC G5 user and a Linux developer port a science
> > package (Eigen) to Mac. This works fine for me on Leopard/Intel,
> but
> > doesn't work for the G5 user.
> >
> > Is _posix_memalign not defined for PowerPC, or is it another
> issue?
> >
> > Thanks,
> > -Geoff
> >  _______________________________________________
>
> Hi Geoff,
>
> posix_memalign is not necessary in OSX.
>
> >From some alloc.c code I stumbled across:
>
> #elif defined(__APPLE__)
>     /*
>      * malloc in Mac OS X guarantees 16 byte alignment.  And large
>      * memory allocations are guaranteed to be page-aligned.  See
>      *
> http://developer.apple.com/documentation/Performance/Conceptual/
>      * ManagingMemory/Articles/MemoryAlloc.html
>      * --
>      * ekato Jan 23 2006
>      */
>     if (sizeof(ScmCell) <= 16)
>         p = malloc(size);
>     else
>         PLAIN_ERR("cannot ensure memory alignment");
>
> As noted in the comments above and the developer info, OSX
> guarantees 16 byte alignment. So, you'll have to find some
> way add in the code that sets this in the Eigen code.
>
> Ian Kaufman
> Research Systems Administrator
> Jacobs School of Engineering
>

Oh, and I forgot. Since it works on your Intel Mac, but not
on your PPC/G5 Mac, and it is coming from Linux code, you
may be running into an endianness issue.

Ian Kaufman
Research Systems Administrator
Jacobs School of Engineering

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