Re: [ublas] ublas Digest, Vol 130, Issue 8

Subject: Re: [ublas] ublas Digest, Vol 130, Issue 8
From: palik imre (imre_palik_at_[hidden])
Date: 2016-01-22 04:18:24

vectorisation: -Ofast vectorises even better.  (Though the results might be off somewhat)BTW, this is one of the big issues with the vanila ublas implementation.  I mean that it doesn't vectorise.

    On Friday, 22 January 2016, 0:30, "ublas-request_at_[hidden]" <ublas-request_at_[hidden]> wrote:
 

 From: nasos <nasos_i_at_[hidden]>
To: ublas_at_[hidden]
Subject: Re: [ublas] Matrix multiplication performance
Message-ID: <BLU436-SMTP2214ADFAE38F3F9E1812E2999C30_at_phx.gbl>
Content-Type: text/plain; charset="windows-1252"; Format="flowed"

Michael,
please see below

On 01/21/2016 05:23 PM, Michael Lehn wrote:
> Hi Nasos,
>
> first of all I don?t want to take wrong credits and want to point out 
> that this is not my algorithm.  It is based on
>
> http://www.cs.utexas.edu/users/flame/pubs/blis2_toms_rev3.pdf
>
> https://github.com/flame/blis
>
> For a few cores (4-8) it can easily made multithreaded.  For 
> many-cores like Intel Xeon Phi this is a bit more
> sophisticated but still not too hard.
Setting up Phis is indeed an issue, especially because they are "locked" 
with icpc. Openmp is working properly though.

> The demo I posted does not use micro kernels that exploit SSE, AVX or
> FMA instructions.  With that the matrix product is on par with Intel 
> MKL.  Just like BLIS. For my platforms I wrote
> my own micro-kernels but the interface of function ugemm is compatible 
> to BLIS.
>
If you compile with -O3 I think you are getting  near optimal SSE 
vectorization. gcc is truly impressive and intel is even more.