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Altera_Forum's avatar
Altera_Forum
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9 years ago

get_global_id(0) cause much latency ?

Hi I'm trying to compare the performance of FPGA and GPU based on image processing algorithm. I've found that there's a 10ms different when using the get_global_id(0) and not using it. The kernel ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
9 years ago

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You can see the latency values by hovering your mouse over the blocks in the "System Viewer" tab of the report.

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Thanks a lot!

I saw that the load in the kernel that compile optimized for NDRange (containing get_globle_id) is in burst-coalesced mode and the single pipeline one is in prefetching mode, and the latency of burst-coalesced mode is huge(159) compare to prefetching(2).

Is there anyway to achieve what I was trying to do in the first place: creating multiple kernel copies by using num_compute_unit and get_globle_id and not enduring the huge latency caused by the burst-coalesced mode?

Beside from launch them separately under different queues of cause:)