Re: Kernel FP software completion
I hope this is what I think it is! What has been missing for me to
use Linux/Alpha instead of DEC-Unix/Alpha is the floating point
problem. Am I right in assuming that with this kernel correction,
that DEC-Unix floating point errors (allowed lets say with the
DEC-Unix FORTRAN compiler -fpe1 switch) will now work correctly under
Linux/Alpha? Further, will this kernel ability allow one to not
utilize the -mieee switch on the g77 compiler and, hence, allow code
to run faster under Linux/Alpha?
>Date: Tue, 26 Jan 1999 14:25:09 +0100
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>From: "David A. van Leeuwen" <david@tm.tno.nl>
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>>>>>> "Stephane" == Stephane Bortzmeyer <bortzmeyer@pasteur.fr> writes:
>
> Stephane> On Monday 25 January 1999, at 23 h 39, the keyboard of
> Stephane> John Goerzen <jgoerzen@complete.org> wrote:
> >> So, my question is, why does Alpha suddenly require math
> >> emulation when it didn't before? Isn't FP one of the Alpha's
> >> strongest areas?
>
> Stephane> It is *not* FP emulation and it has nothing to do with
> Stephane> i387 emulation on the PC.
>
>That is what i thought, too. The Alpha doesn't seem to have `weird'
>numbers such as NaN (0/0, or log(-1)), +Inf (1/0) or -Inf(log(0)),
>which are defined for IEEE arithmetic. Indeed, compiling -mieee will
>generate code to deal with these constants.
>
>In c, you could say
>
>#include <huge_val.h>
>
>float min = -HUGE_VAL;
>for (i=0; i<N; i++ ) {
> if (a[i]>min) min=a[i];
>}
>
>This normally needs to be compiled -mieee on Alpha. I suspect that
>the new kernel config parameter relaxes this condition.
>
>---david
>
>
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