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Re: underflow exceptions

On Fri, May 25, 2012 at 11:04:17AM +0000, Joseph S. Myers wrote:
> This is probably an instance of the same issue as in bug 14152, but for 
> fma.  I suggest updating the summary of that bug to reflect that the issue 
> applies to this fma test as well, and changing UNDERFLOW_EXCEPTION to 
> UNDERFLOW_EXCEPTION_OK in the test (with a comment above it referring to 
> bug 14152).

Thanks.  I made a comment in the BZ a will post patch shortly.

> I generally do libm testing with --disable-multi-arch so that it's 
> predictable what version of a function is used and to be sure that the 
> generic versions are properly fixed.  In this case, I suspect you had 
> multi-arch enabled, but a processor without FMA4 instructions, and this 
> combination meant your testing ended up using the dbl-64 version of 
> s_fma.c whereas mine used the ldbl-96 one (and this issue of missing 
> underflow exceptions may only arise when the operation is done in the same 
> internal precision as the final result).

Thanks for the pointer, my machine definitely hasn't FMA4, --disable-multi-arch


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