Scientific computing and parallel computing C++23/C++26

Bruce Carneal bcarneal at
Sat Jan 15 11:24:44 UTC 2022

On Saturday, 15 January 2022 at 10:35:29 UTC, Guillaume Piolat 
> On Saturday, 15 January 2022 at 09:03:11 UTC, Nicholas Wilson 
> wrote:
>> from what I understand unified memory allows the GPU to access 
>> the host RAM with the same pointer. This reduces the total 
>> memory consumed by the program, but to get to the GPU the data 
>> must still cross the PCI-e.
> Exactly. I remember that in 2013 "Unified Memory Access" on 
> NVIDIA was underwhelming, performing worse than pinned transfer 
> + GPU memory access.

Exactly++.  Pinned buffers + async HW copies always won out for 

I imagine there could be scenarios where programmatic 
peeking/poking from either side wins but I've not seen them, 
probably because if your data flows are small enough for that to 
win you'd just fire up SIMD and call it a day.

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