Re: [Jchat] was [Jprogramming] Gustafson's Unums Revisited

[Erling Hellenäs]

This is how JWithATwist handles the same situation:

{ |<. 0.5 + 10 ^ 14 }
 100000000000000
{ |<. 0.5 + 10 ^ 15 }
 1000000000000000
{ |<. 0.5 + 10 ^ 16 }
Domain error
{ |>. 0.5 + 10 ^ 14 }
 100000000000001
{ |>. 0.5 + 10 ^ 15 }
 1000000000000001
{ |>. 0.5 + 10 ^ 16 }
Domain error
No ones invented. No data loss. Domain error if you use Floor or Ceiling 
on a double when precision is higher than 1.

/Erling


On 2016-08-22 10:16, Erling Hellenäs wrote:
0j3 ": 0.5+10^14

100000000000000.500

The strange result under discussion. How does J create this result?

0j3 ": <. 0.5+10^14

100000000000001.000

I must admit I don't understand why this happens. It is loss of 
precision?

0j3 ": 0.5+10^15

1000000000000000.500

Here we have loss of precision:

0j3 ": 0.5+10^16

10000000000000000.000

/Erling


On 2016-08-20 19:38, Raul Miller wrote:
If loss of precision is a problem, you should be using extended 
precision
numbers (or rationals) for your values.

And, of course, you should be careful to use operations whose results 
are
extended precision numbers (or rationals) for the values you are working
with.

For example:

    <.1r2+10^13x

10000000000000


Thanks,



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