Vc at MIC

[Matthias Kretz]

On Wednesday 21 August 2013 21:48:19 Kulakov, Igor wrote:
> We see significant differences in tracking results with Vc-0.99 and Vc-0.7.2
> using ICC-13.1.0. For example number of broken fast tracks (clones for ref
> set) is factor of 7(!) different. (see numbers below) Meanwhile with
> VC_IMPL=Scalar both Vc-0.99 and Vc-0.7.2 give same result.
> 
> Do you have any suggestions how to proceed?

Wow, that's bad.
It's hard to guess where this is coming from so I need you to find the guilty 
function(s) in Vc.

You should look through the unit tests in detail whether any of the failures 
happen in functions that you use. If this is the case, let me know and I'll 
give priority to those.

If not, then something breaks that doesn't have a test or where the test isn't 
thorough enough. You'd have to find the place where it breaks and deduce the 
function in Vc that is broken. It might be a miscompilation in which case this 
may turn into a Heisenbug...

Q: The results below are for AVX?

Cheers,
	Matthias

> Vc-0.99:
>  ---- Global Performance 10 events Statistic ----
> Track category         :  Eff   / Clones | All Reco | All MC
> Allset    efficiency   : 0.920  / 0.290  | 7119  | 7740
> Refset    efficiency   : 0.982  / 0.136  | 910  | 927
> Extra     efficiency   : 0.911  / 0.310  | 6209  | 6813
> Rest      efficiency   : 0.898  / 0.727  | 79  | 88
> Ghost     probability  : 0.129 | 917
> All reco tracks/ev : 711.900
> Reconstruction Time Real =    767.606 ms, CPU =    767.000 ms,
> parallelization speedup: 0.998
> 
> Vc-0.7.2:
>  ---- Global Performance 10 events Statistic ----
> Track category         :  Eff   / Clones | All Reco | All MC
> Allset    efficiency   : 0.944  / 0.113  | 7304  | 7740
> Refset    efficiency   : 0.980  / 0.020  | 908  | 927
> Extra     efficiency   : 0.939  / 0.126  | 6396  | 6813
> Rest      efficiency   : 0.909  / 0.773  | 80  | 88
> Ghost     probability  : 0.127 | 929
> All reco tracks/ev : 730.400
> Reconstruction Time Real =    146.283 ms, CPU =    145.000 ms,
> parallelization speedup: 0.981
> 
> ________________________________________
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>[please enable javascript to see the address]] on behalf of Matthias Kretz
>[please enable javascript to see the address]] Sent: Friday, August 16, 2013 10:33 AM
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> Subject: Re: Vc at MIC
> 
> On Tuesday 13 August 2013 20:19:52 Zyzak, Maksym wrote:
> > I have compiled Vc-0.99.71 on the computer with MIC cards. And the test
> > are
> > failed. For the compilation I used icc 13.1.0.
> 
> I recommend to always update ICC to the latest version. I use ICC 13.1.2
> 20130514. There were some really strange miscompiles with the older
> compilers.
> > The CPU is Intel(R) Xeon(R)
> > CPU E5-2680. The log of test is given below. Can you please suggest what
> > can be the problem? Should I use another version of Vc?
> 
> There are failing tests for me as well, but the failures are in very special
> features. Fixing those requires a lot of work. Most of the recent failures
> I fixed were ICC bugs.
> 
> --
> Dipl.-Phys. Matthias Kretz
> 
> Web:   http://compeng.uni-frankfurt.de/?mkretz
> 
> SIMD easy and portable: http://compeng.uni-frankfurt.de/?vc
> 
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-- 
Dipl.-Phys. Matthias Kretz

Web:   http://compeng.uni-frankfurt.de/?mkretz

SIMD easy and portable: http://compeng.uni-frankfurt.de/?vc