[Bug target/32180] Paranoia UCB GSL TestFloat libm tests fail - accuracy of recent gcc math poor

["kargl at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #10 from kargl at gcc dot gnu dot org  2007-06-04 17:32 -------
(In reply to comment #7)
> >> kargl@gcc.gnu.org
> >> IEEE 754 does not discuss any of the functions you list above.  In fact,
> >> IEEE 754 places requirements on exactly one function in libm, and that is
> >> sqrt(), which must be exact in all rounding modes.
> 
> 
> I did a search of this document for "sqrt". Adobe reader says the word is not
> there.
> 
> DRAFT Standard for Floating-Point Arithmetic P754 - Draft 1.3.0
> Modified at 17:15 GMT on February 23, 2007
> http://www.validlab.com/754R/drafts/archive/2007-02-23.pdf

Compare the current working draft of the revised IEEE 754 standard
to the standing Standard is similar to a comparison of a Boeing 747
to the Wright brothers' aircraft.  The standing IEEE 754 standard
is 23 pages in total length.

Here is the text concerning square root:

  5.2. Square Root
  The square root operation shall be provided in all supported formats. The
  result is defined and has a positive sign for all operands >= 0, except that
  sqrt(­0) shall be ­0. The destination format shall be at least as wide as the
  operand's. The result shall be rounded as specified in Section 4.

There are a few functions described in the Appendix, which contains this
disclaimer: "(This Appendix is not a part of ANSI/IEEE Std 754-­1985, IEEE
Standard for Binary Floating-Point Arithmetic.)"


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32180