From: Phillip Gawlowski <pg@...>
Date: 2010-01-15T14:32:27+09:00
Subject: Re: Float Points error

On 15.01.2010 05:56, THAKUR PRASHANT SINGH wrote:

> While retrieving from array I get some number like 22.09000015.
>
> So when I do groupings I miss out my original number as 22.09<
> 22.09000015
>
> Where as it should come in a group where numbers are 22.09>= 22.09

Floats aren't exact, they are approximations: IEEE 754-2008 
<http://en.wikipedia.org/wiki/IEEE_754-2008>

> I wish to have last condition returning true.Is there any simple way to
> do that as my dataset contains around a million numbers.

Short of implementing a #rounding method (1.8.6 Core does only integer 
rounding, after a curious check; STDLIB, 1.8.7 and 1.9.1 might have a 
different behavior) to the accuracy you need: No.

Or you could implement a custom comparison operator that does what you need.

> If I use conversion to string and back to to_f I lose time of
> approximately 10 secs for each 7000 rows.

You'll loose time when computing with Floats, anyway, since outside of 
vector-based CPUs (IIRC), the performance of performing maths on floats 
is terrible (in relative terms).

--
Phillip Gawlowski