From mboxrd@z Thu Jan  1 00:00:00 1970
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
In-reply-to: Your message of "Sun, 02 Oct 2011 18:38:00 +0200."
	<20111002163800.GA12773@polynum.com>
References: <20111002163800.GA12773@polynum.com>
Date: Sun,  2 Oct 2011 10:52:27 -0700
From: Bakul Shah <bakul@bitblocks.com>
Message-Id: <20111002175227.2D7F1B856@mail.bitblocks.com>
Subject: Re: [9fans] circular fonctions: precision?
Topicbox-Message-UUID: 2f45cc2a-ead7-11e9-9d60-3106f5b1d025

On Sun, 02 Oct 2011 18:38:00 +0200 tlaronde@polynum.com  wrote:
> Hello,
>
> Is there some documentation about the precision of the circular (i.e
> trigonometric) fonctions, depending on the (plan9) implementation and
> the hardware?

Do you mean precision (number of significant bits) or accuracy
(closeness to true value)? For a double the precision is 52
bits, for a float 23.

> To my limited knowledge, an OS is integer based, so the floating
> point support is mainly "user space" and is, despite IEEE754 and due to
> the interaction between hardware, software, and programmer, really
> floating, but is there a range given for the association of OS/hardware
> telling that say sin(r) or asin(s) is accurate, at worst, at some
> epsilon near?

It depends on the algorithm used, not on the OS. The C
standard leaves accuracy upto the implementation. If you care,
you can compare the result of a C function with what bc(1)
computes for the same function (by using a suitably large
scale).