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Re: Effects of newly introduced -mpcX 80387 precision flag
- From: Bradley Lucier <lucier at math dot purdue dot edu>
- To: Uros Bizjak <ubizjak at gmail dot com>
- Cc: Bradley Lucier <lucier at math dot purdue dot edu>, Richard Henderson <rth at redhat dot com>, gcc mailing list <gcc at gcc dot gnu dot org>, Richard Guenther <richard dot guenther at gmail dot com>
- Date: Thu, 3 May 2007 15:01:04 -0400
- Subject: Re: Effects of newly introduced -mpcX 80387 precision flag
- References: <D78A6CE9-4B67-46AC-9279-732C64E068C6@math.purdue.edu> <4639FB91.1050802@gmail.com> <821B0FDF-532D-4075-9D87-1D9172BE5AF8@math.purdue.edu> <463A2DE3.7070507@gmail.com>
On May 3, 2007, at 2:45 PM, Uros Bizjak wrote:
Bradley Lucier wrote:
On May 3, 2007, at 11:11 AM, Uros Bizjak wrote:
Could you please post a patch with suggested wording about this
option (I was trying to write something similar to the warning
that icc has in its documentation about precision settings).
How about this? It perhaps reflects my own biases, but the term
"catastrophic loss of accuracy" is sometimes used in the technical
sense that I mean here. For the performance figures, I used the
figures you gave in your e-mail but add "or more" to be on the
safe side.
What about "significant loss of accuracy" as these options probably
won't cause a nuclear reactor meltdown ;)
Well, I did some googling, and the technical term I was thinking of
was "catastrophic cancellation". So how about
Note that some mathematical routines in such libraries could suffer
significant loss of accuracy, typically through so-called
"catastrophic cancellation", when this option is used to set the
precision to less than extended precision.
Brad