> Otherwise I don't think we can justify the additional maintenance
> cost/risk, sorry.
This is am extremely self-contained and easy to test piece of code.
Look at the history; the total edits to the function since the
beginning of git in 2005 are:
- A theoretical bug fix to handle zero arguments
On Fri, 15 Aug 2014 20:49:16 +0800 Zhaoxiu Zeng wrote:
> Because some architectures (alpha, armv6, etc.) don't provide hardware
> division,
> the mod operation is slow! Binary GCD algorithm uses simple arithmetic
> operations,
> it replaces division with arithmetic shifts, comparisons, and subt
Here's a variant using the even-odd speedup:
(Feel free to add my S-o-b if you use it.)
/*
* This implements Brent & Kung's "even-odd" variant of the binary GCD
* algorithm. (Often attributed to Stein, but as Knith has noted, appears
* a first-century Chinese math text.)
*
* First, find the
On Fri, Aug 15, 2014 at 04:16:01PM -0400, George Spelvin wrote:
> What I'd like is a better way to automatically configure "divide is
> slow" from an architecture.
So the usual thing and have arch/*/Kconfig select the fancy one if it
doesn't have a hardware divide instruction.
For instance:
arch
> So I looked at wikipedia (I wasn't aware of this algorithm, clever
> though), and am still somewhat puzzled by your 'r'.
>
> What's 'wrong' with their iterative version, or what's better about your
> 'r' stuff?
I need to look more carefully, but it looks nifty.
Basically, it's avoiding the usu
在 2014/8/15 21:58, Peter Zijlstra 写道:
> On Fri, Aug 15, 2014 at 08:49:16PM +0800, Zhaoxiu Zeng wrote:
>> Because some architectures (alpha, armv6, etc.) don't provide hardware
>> division,
>> the mod operation is slow! Binary GCD algorithm uses simple arithmetic
>> operations,
>> it replaces divi
On Fri, Aug 15, 2014 at 08:49:16PM +0800, Zhaoxiu Zeng wrote:
> Because some architectures (alpha, armv6, etc.) don't provide hardware
> division,
> the mod operation is slow! Binary GCD algorithm uses simple arithmetic
> operations,
> it replaces division with arithmetic shifts, comparisons, and
Because some architectures (alpha, armv6, etc.) don't provide hardware division,
the mod operation is slow! Binary GCD algorithm uses simple arithmetic
operations,
it replaces division with arithmetic shifts, comparisons, and subtraction.
Signed-off-by: Zhaoxiu Zeng
---
lib/Kconfig | 15 +++
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