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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