Re: [boost] SIMD implementation of uBLAS

Subject: Re: [boost] SIMD implementation of uBLAS
From: Joel Falcou (joel.falcou_at_[hidden])
Date: 2013-05-29 09:05:55

On 29/05/2013 15:00, Nasos Iliopoulos wrote:
> As a matter of fact I am surprised by the progress  of the compilers 
> auto-vectorization facilities the last few years, that make me -doubt- 
> the need for explicit vectorization any more. The GSOC project will 
> make it clear for us. An added benefit on relying on compiler is that 
> future vector instructions come for free. A disadvantage is of course 
> the non-guarantee that auto-vectorization will work but I find this 
> rarely the case.

I beg to differ, you're in for some nasty surprises. It basically works 
for simple operations on simple one-level loops with easily inferred 
loop boundaries.
Also, those stuff are very fragile and based on vendor willingness to do 
whatever.

In multiple actual cases we had to deal with in both academic and 
industrial context, the autovectorizer was rapidly confused even for 
rather simple c++ code.