Hi Aseem,

This maybe caused by memory access collisions and/or lack of coalesced memory access. This technical report gives some pointers:
https://www2.eecs.berkeley.edu/Pubs/TechRpts/2016/EECS-2016-143.pdf
Do you use atomic operations? Or maybe you have too many thread fences?
I have no problem starting many threads: the number of threads alone is not the issues.

Cheers,
Sven


Op 6-6-2018 om 8:37 schreef aseem hegshetye:
Hi,
Does GPU speed exponentially drop as number of threads increase beyond a certain number?. I used to allocate number of threads= number of transactions in data under consideration.
For Tesla K80 I see exponential drop in speed above 30290 Threads. 
If true, is it a best practice to keep number of threads low and iterate over the data to get results at optimum speed. 
How to find best number of threads for a GPU?

Thanks
Aseem


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