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On 9/20/2010 10:07 PM, Mike McGonagle wrote:
On Mon, Sep 20, 2010 at 9:35 AM, KHMan wrote:
In libm, the software implementation of floor() seems normal enough. Looking
at i387 assembly code in libm, the rounding mode is indeed changed, but it
is restored, pretty standard stuff -- no one in the right mind would have
left it as changed.

Since there is nothing amiss on Tony Finch's Mac OS version of Lua, I don't
think Mac OS or FreeBSD developers would have missed such a simple thing.

I guess that the 'something' is likely to be found in additional libraries
or code that the OP is using, like a heavy maths library that can have its
floating point modes adjusted and assumes that it is king of its

I don't think this could be it, as I don't have anything other than
the base install for 5.1.4 running. I can only assume that this might
stem from how the G4 (an IBM chip) as opposed to the Intel that the
Mac now uses.

Thanks for the update, it is appreciated.

Mac_OSX_Numerics.pdf in the PowerPC section say the default is round-to-nearest. The rounding mode can be checked using fegetround() -- if it's round to -INF, then I suppose it would support the current hypothesis. Hard to see anything else whilst doing normal arithmetic would produce a -0.0 other than the change of rounding mode.

On PPC floor(), from:
it does not look like floor() is going to change any of the processor's rounding flags. There is no native floor() but only a faster version in math.h in the same source tree.

Kein-Hong Man (esq.)
Kuala Lumpur, Malaysia