On Feb 11 2007, Falk Hueffner wrote:
> [EMAIL PROTECTED] writes:
>
> > In tracking down issues with ganglia/rrdtool, I found that floor()
> > is not working properly in testing on my Avanti - it always seems to
> > return zero:
> >
> > [EMAIL PROTECTED]:~$ cat junk.c
> > #include <stdio.h>
> > #include <math.h>
> >
> > int main()
> > {
> > double x = 1.1;
> >
> > printf("floor(%f) = %f\n", x, floor(x));
> >
> > return(0);
> > }
> > [EMAIL PROTECTED]:~$ gcc junk.c -o junk -lm
> > [EMAIL PROTECTED]:~$ ./junk
> > floor(1.100000) = 0.000000
> >
> > The same code on EV56 produces the expected result.
> >
> > Anyone have any ideas or recommendations?
>
> The EV4 FPU cannot round to minus infinity, as glibc's floor wants to
> do, so the kernel emulates this. So it's almost certainly a kernel
> bug.
<snip>
Or pilot error :-( I finally got a chance to look more into this,
and I see that I have gaffed. I did not have the math-emu module
loaded. Once loaded, floor() (and other stuff) works fine.
Maybe everyone except me knew to have math-emu loaded? I was
kind of surprised it was not built-in. Is this intended?
Cheers,
Craig
Here's the Kconfig help for MATHEMU:
This option is required for IEEE compliant floating point arithmetic
on the Alpha. The only time you would ever not say Y is to say M in
order to debug the code. Say Y unless you know what you are doing.
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