lucene-solr-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Yonik Seeley <yo...@lucidimagination.com>
Subject Re: Tuning caching of geofilt queries
Date Fri, 10 Aug 2012 18:11:27 GMT
On Fri, Aug 10, 2012 at 1:47 PM, David Smiley (@MITRE.org)
<DSMILEY@mitre.org> wrote:
> Information I've read vary on exactly what is the accuracy of float
> vs double but at a kilometer there's no question a double is overkill.

Back of the envelope:

23 mantissa bits + 1 implied bit == 24 effective mantissa bits in a 32
bit float.

40,000 km circumference / (2^24) = .0024 km  (i.e. our resolution at
the equator is 2.4m at best - there will be some lost unused space at
the beginning and end of the +-180 number-line).

Is that in line with what you've read?

-Yonik
http://lucidworks.com

Mime
View raw message