Even if we take care of the zero case, a fuzzy residue will deliver
random errors much higher than the small errors which naturally affects
real numbers? Multiplied with a big number and then the lost precision
of the subtraction can make these errors very significant? /Erling
On 2017-09-15 17:25, Erling Hellenäs wrote:
Hi all!
OK. I guess there is some way to implement this so that both Floor and
Residue are fuzzy without having the circular dependency. It seems to
basically be the implementation we have.
It seems Floor gives the closest integer within comparison tolerance
in the way it is specified then.
9!:19 [ 5.68434e_14
25j5": (9!:18'') * 5729082486784839 % 196
1.66153
25j5":a=: 5729082486784839 % 196
29230012687677.75000
25j5": <. a
29230012687678.00000
It means that this result, which we find strange, is according to
specification?
(14^2) | 5729082486784839
0
It also means that this result, which we find correct, is not
according to specification?
196 | 5729082486784839
147
So, now there is a question about if we should live with this
inconsistency or change the specification or the part of the
implementation that is not according to this specification?
I think the efforts to create a consistent algebra is good. However,
in my practical experience I found it important that functions give
correct results. Incorrect results without any fault indication could
mean that the patient dies, the bridge collapses or the company gets
insolvent. Could the zero result really be considered correct? If not,
is there a way in which we could deliver a fault indication instead of
the zero result? This means we should have an error in the integer
case and a NaN in the real case?
Cheers,
Erling Hellenäs
Den 2017-09-15 kl. 14:13, skrev Raul Miller:
Eugene's work should be thought of as specification, rather than
implementation.
That said, chasing through the various implementations of floor for
the various C data types can be an interesting exercise.
Thanks,
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