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Date: Wed, 5 Aug 2020 20:27:02 +0200
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: sha512crypt-opencl / Self test failed (cmp_all(1))

On Tue, Aug 04, 2020 at 03:04:28PM +0200, Solar Designer wrote:
> sha512crypt-opencl works for me on Vega 64 with:
> 
>     Device #0 (1) name:     gfx900
>     Board name:             Radeon RX Vega
>     Device vendor:          Advanced Micro Devices, Inc.
>     Device type:            GPU (LE)
>     Device version:         OpenCL 2.0 AMD-APP (2766.4)
>     Driver version:         2766.4 (PAL,HSAIL) - AMDGPU-Pro  
> 
> but the speed is very poor (for that hardware):
> 
> LWS=64 GWS=262144 (4096 blocks) DONE
> Speed for cost 1 (iteration count) of 5000
> Raw:	65372 c/s real, 5242K c/s virtual

As Claudio pointed out to me, that must have been a temporary glitch -
maybe the GPU was in other use at that time.  Here's what I am getting
now that I rerun the test:

$ ./john -test -form=sha512crypt-opencl 
Device 1: gfx900 [Radeon RX Vega]
Benchmarking: sha512crypt-opencl, crypt(3) $6$ (rounds=5000) [SHA512 OpenCL]... LWS=256 GWS=262144 (1024 blocks) DONE
Speed for cost 1 (iteration count) of 5000
Raw:	129453 c/s real, 5242K c/s virtual

Even forcing it to LWS=64 (which it had autotuned to before), I get
almost the same better speed:

$ LWS=64 ./john -test -form=sha512crypt-opencl 
Device 1: gfx900 [Radeon RX Vega]
Benchmarking: sha512crypt-opencl, crypt(3) $6$ (rounds=5000) [SHA512 OpenCL]... LWS=64 GWS=262144 (4096 blocks) DONE
Speed for cost 1 (iteration count) of 5000
Raw:	127875 c/s real, 4032K c/s virtual

which is reasonable scaling from:

> It also works for me on Tahiti with this ancient driver:
> 
>     Device #0 (3) name:     Tahiti
>     Board name:             AMD Radeon HD 7900 Series  
>     Device vendor:          Advanced Micro Devices, Inc.
>     Device type:            GPU (LE)
>     Device version:         OpenCL 1.2 AMD-APP (1642.5)
>     Driver version:         1642.5 (VM) - Catalyst 14.12(Omega) [supported]
> 
> delivering a saner speed (for that hardware):
> 
> LWS=64 GWS=262144 (4096 blocks) DONE
> Speed for cost 1 (iteration count) of 5000
> Raw:	51150 c/s real, 2621K c/s virtual

Vega 64 is a twice larger GPU at 1.5x higher clock rate than Tahiti, so
a ~3x difference is expected.

Alexander

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