On Thursday, 19 May 2016 at 11:00:31 UTC, Ola Fosheim Grøstad
wrote:
On Thursday, 19 May 2016 at 08:37:55 UTC, Joakim wrote:
On Thursday, 19 May 2016 at 08:28:22 UTC, Ola Fosheim Grøstad
wrote:
On Thursday, 19 May 2016 at 06:04:15 UTC, Joakim wrote:
In this case, not increasing precision gets the more
accurate result, but other examples could be constructed
that _heavily_ favor increasing precision. In fact, almost
any real-world, non-toy calculation would favor it.
Please stop saying this. It is very wrong.
I will keep saying it because it is _not_ wrong.
Can you then please read this paper in it's entirety before
continuing saying it. Because changing precision breaks
properties of the semantics of IEEE floating point.
What Every Computer Scientist Should Know About Floating-Point
Arithmetic
https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html#3377
«Conventional wisdom maintains that extended-based systems must
produce results that are at least as accurate, if not more
accurate than those delivered on single/double systems, since
the former always provide at least as much precision and often
more than the latter. Trivial examples such as the C program
above as well as more subtle programs based on the examples
discussed below show that this wisdom is naive at best: some
apparently portable programs, which are indeed portable across
single/double systems, deliver incorrect results on
extended-based systems precisely because the compiler and
hardware conspire to occasionally provide more precision than
the program expects.»
The example he refers to is laughable because it also checks for
equality.
The notion that "error correction" can fix the inevitable
degradation of accuracy with each floating-point calculation
is just laughable.
Well, it is not laughable to computer scientists that accuracy
depends on knowledge about precision and rounding... And I am a
computer scientists, in case you have forgotten...
Computer scientists are no good if they don't know any science.
