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Date: Sun, 2 Nov 2014 13:02:48 -0900
From: Royce Williams <>
To: john-dev <>
Subject: Re: descrypt speed

On Sun, Nov 2, 2014 at 12:19 PM, magnum <> wrote:

> On 2014-11-02 18:59, Royce Williams wrote:
>> On Thu, Oct 30, 2014 at 9:33 PM, magnum <> wrote:
>>> On 2014-10-31 06:02, Royce Williams wrote:
>>>> On a GTX970, shouldn't this be sm_52?
>>> You can force this by editing NVCC_FLAGS in Makefile. Add something like
>>> "-arch sm_50" (or 52). But I doubt it will make much difference and it
>>> will
>>> only affect CUDA formats.
>> In my system with both an sm_20 and an sm_50 card, when running solely
>> descrypt-opencl (not CUDA), the ptxas info shows that sm_50 is involved in
>> some way.  Is this cosmetic?
> OpenCL compiles a suitable (different) kernel for each and you do not have
> to configure anything.

What's giving me pause is that without changing anything on either system,
descrypt-opencl is appropriately using sm_20 and sm_50 on my heterogeneous
system, but is only using sm_20 on my GTX750 system.  Previously, the
latter system was happily using sm_52.  I am not sure what changed.

> You can configure CUDA for compiling several archs at once, see "nvcc
> --help". It something like "-gencode arch=compute_20,code=sm_20 -gencode
> arch=compute_50,code=sm_50" (added to NVCC_FLAGS instead of just -arch
> sm_xx). The one most suitable of them will be picked at runtime.

Interesting -- I'll try that.


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