Message-ID: <20120731201350.GA5187@cs.cas.cz>
Date: 2012-07-31T20:13:50Z
From: Petr Savicky
Subject: protential rounding error concern
In-Reply-To: <CACXG3Gh58Mv+UqtWV9Ja99rvNJJqeaz8gWMbKqkGYqm6aD9SyQ@mail.gmail.com>
On Tue, Jul 31, 2012 at 03:45:14PM -0400, Jie wrote:
> Dear All,
>
> I am running a r code on 32bit win, involving absolutely small numbers.
> Although I tried sth like the ratio of numers like 10^(-100) and did not
> have issue to get the correct answer,
> but still a little concerned about it.
> Could anyone give some suggestion or have any experience?
Hi.
Numbers of the order 10^(-100) are still relatively far from the lower
limit and are represented with full precision, which is 53 bits.
The smallest number representable in full precision is 2^-1022 = 2.225074e-308
and the smallest representable number (in limited precision) is 2^-1074 =
4.940656e-324.
See
http://en.wikipedia.org/wiki/Double_precision_floating-point_format
for more detail.
Hope this helps.
Petr Savicky.