Re: SIGFPE, Arithmetic exception. "Value optimized out" when using --ffast-math

[Tim Prince <n8tm at aol dot com>]

On 7/2/2011 11:18 AM, Steve Kargl wrote:
> On Sat, Jul 02, 2011 at 02:36:21PM +0200, Dominique Dhumieres wrote:
> >

> Associative is a forbidden transformation in the standard.
>
> Note 7.18 [1] form F2003 has the following forbidden transformation
>
> (X + Y) + Z          X + (Y + Z)
> (X * Y) - (X * Z)    X * (Y - Z)
> X * (Y - Z)          X*Y-X*Z
>
> If -funsafe-math-optimization any of these, then you get what
> you asked for. (NO, I haven't looked to see what the option
> allows).
>
> [1] Yes, I know a Note is non-normative text.

The Fortran list of permitted and forbidden associations has been 
carried over since the f66 standard.  It seems to have passed the test 
of practical usage time after time.
Is there a combination of options which observes the standard with 
respect to parentheses, but permits vectorization of sum reduction?

--
Tim Prince