Re: [patch V2] lib: GCD: add binary GCD algorithm

On Wed, Apr 27, 2016 at 12:20:33PM -0400, George Spelvin wrote: > The frequent "if (USE_FFS)" conditions seem to clutter the code. > Would it be easier to read if the two variants were just separated? > The function is short enough that the duplication isn't too severe. Yes please, this is _MUCH_

Re: [patch V2] lib: GCD: add binary GCD algorithm

On Wed, Apr 27, 2016 at 12:20:33PM -0400, George Spelvin wrote: > The frequent "if (USE_FFS)" conditions seem to clutter the code. > Would it be easier to read if the two variants were just separated? > The function is short enough that the duplication isn't too severe. Yes please, this is _MUCH_

Re: [patch V2] lib: GCD: add binary GCD algorithm

On Wed, 27 Apr 2016 16:05:50 +0800 zengzhao...@163.com wrote: > From: Zhaoxiu Zeng > > Because some architectures (alpha, armv6, etc.) don't provide hardware > division, > the mod operation is slow! Binary GCD algorithm uses simple arithmetic > operations, > it

Re: [patch V2] lib: GCD: add binary GCD algorithm

On Wed, 27 Apr 2016 16:05:50 +0800 zengzhao...@163.com wrote: > From: Zhaoxiu Zeng > > 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

Re: [patch V2] lib: GCD: add binary GCD algorithm

I replicated your results in 32- and 64-bit x86: - If __ffs (gcc's __builtin_ctz) is available, the basic (non-even/odd) binary GCD algorithm is faster than the divsion-based or even/odd. - If shifting down has to be done in a loop, the even/odd binary algorithm is fastest. I tried a few

Re: [patch V2] lib: GCD: add binary GCD algorithm

I replicated your results in 32- and 64-bit x86: - If __ffs (gcc's __builtin_ctz) is available, the basic (non-even/odd) binary GCD algorithm is faster than the divsion-based or even/odd. - If shifting down has to be done in a loop, the even/odd binary algorithm is fastest. I tried a few

[patch V2] lib: GCD: add binary GCD algorithm

From: Zhaoxiu Zeng 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. I have

[patch V2] lib: GCD: add binary GCD algorithm

From: Zhaoxiu Zeng 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. I have compiled successfully with