Re: [gomp4 00/14] NVPTX: further porting

[Bernd Schmidt <bschmidt@redhat.com>]

On 10/21/2015 05:18 PM, Alexander Monakov wrote:
> On Wed, 21 Oct 2015, Bernd Schmidt wrote:
>
>> On 10/20/2015 08:34 PM, Alexander Monakov wrote:
>>> This patch series ports enough of libgomp.c to get warp-level parallelism
>>> working for OpenMP offloading.  The overall approach is as follows.
>>
>> Could you elaborate a bit what you mean by this just so we understand each
>> other in terms of terminology? "Warp-level" sounds to me like you have all
>> threads in a warp executing in lockstep at all times. If individual threads
>> can take different paths, I'd expect it to be called thread-level parallelism
>> or something like that.
>
> Sorry, that was unclear.  What I meant is that there is a degree of
> parallelism available across different warps, but not across different teams
> (because only 1 team is spawned), nor across threads in a warp (because all
> threads in a warp except one exit immediately -- later on we'd need to
> keep them converged so they can enter a simd region together).

I see. That ensures that you wouldn't see any problems related to 
reconvergence yet. I think I would like to see something with actual 
thread parallelism to demonstrate at least as a proof of concept that 
the synchronization code is roughly sane.


Bernd