From: Eric Dumazet <eric.dumazet@gmail.com>
To: Dave Taht <dave.taht@gmail.com>
Cc: codel@lists.bufferbloat.net
Subject: Re: [Codel] fp sqrt vis int sqrt?
Date: Fri, 04 May 2012 19:47:32 +0200 [thread overview]
Message-ID: <1336153652.3752.361.camel@edumazet-glaptop> (raw)
In-Reply-To: <CAA93jw7Mo0QdhgKk2p+LeT_esv6TSA2qhgK5Xg7YzcDHX=z3WA@mail.gmail.com>
On Fri, 2012-05-04 at 10:23 -0700, Dave Taht wrote:
> In looking over the (lack of) compiler support for fp in the kernel,
> it seems simplest to load up a table from userspace for the
> interval/sqrt(count) calculation.
Well, you could have a small table (not from userspace, thats really not
needed at all) for the 16 first sqrt values.
More over, for the first sqrt values you can use reciprocal divide so
that we dont have a divide anymore (see include/linux/reciprocal_div.h),
and you can have a very precise sqrt this way, not an integral one.
With count >= 16, the error you mention becomes small.
next prev parent reply other threads:[~2012-05-04 17:47 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-04 15:11 Dave Taht
2012-05-04 15:14 ` Jim Gettys
2012-05-04 15:19 ` Dave Taht
2012-05-04 15:26 ` Jim Gettys
2012-05-04 15:56 ` Eric Dumazet
2012-05-04 17:23 ` Dave Taht
2012-05-04 17:43 ` Dave Taht
2012-05-04 17:44 ` Dave Taht
2012-05-04 17:46 ` Dave Taht
2012-05-04 23:42 ` Kathleen Nichols
2012-05-05 0:01 ` Dave Taht
2012-05-04 17:47 ` Eric Dumazet [this message]
2012-05-04 18:26 ` Eric Dumazet
2012-05-04 18:39 ` Dave Taht
2012-05-04 18:50 ` Eric Dumazet
2012-05-04 19:04 ` Dave Taht
2012-05-04 19:16 ` Eric Dumazet
2012-05-05 8:14 ` Eric Dumazet
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