Re: current development

[Philippe Michel]

On Wed, Dec 04, 2019 at 10:07:18AM +1300, Joseph Heled wrote:

> Yes, info says multithread support. It says SSE/SSE2 support. What
> about SSE3/4 etc, or they confer no real improvement over SSE2?

SSE3/4 probably wouldn't make a meningful difference. AVX helps but 
these SIMD instructions are used only in the forward propagation 
computations.

When I looked at profiling info, with SSE2, time was spent, roughly, 1/3 
in inputs computations, 1/3 in forward propagation and 1/3 in the rest, 
mostly moves generation and match equity calculations. So using AVX 
instead of SSE2 would be at best a 1/6 gain.

Debian's choice of building with SSE2 support seems reasonable for 
amd64. For 32 bits architectures, I don't know at which point SSE2 
instructions are guaranteed to be available (are they in i686 ?), but if 
they build without SIMD instructions to support older CPUs the cost for 
users doing rollouts or thorough analyses will be significant.