topic Re:DCP++ subgroup in Intel® oneAPI DPC++/C++ Compiler

DCP++ subgroup

RitaChu — Sat, 04 Dec 2021 23:52:45 GMT

Hi,

What is the difference between subgroup shuffle and group_broadcast. To me they seem to generate same results if you give the same index to shuffle/broadcast.

Thanks

Re:DCP++ subgroup

SantoshY_Intel — Mon, 06 Dec 2021 08:47:36 GMT

Hi,

Thanks for reaching out to us.

The sub-group broadcast function can be thought of as a specialized version of the general-purpose shuffle function, where the shuffle index is the same for all work-items in the sub-group.

>>"To me they seem to generate same results if you give the same index to shuffle/broadcast."

When the shuffle index is known to be the same for all work-items in the sub-group, then we will get the same results for both shuffle and broadcast.

But, using broadcast instead of shuffle provides the compiler additional information and may increase performance on some implementations.

Thanks & Regards,

Santosh

Re: Re:DCP++ subgroup

RitaChu — Mon, 06 Dec 2021 16:52:03 GMT

@SantoshY_Intel thanks for the explanation.

Re: DCP++ subgroup

SantoshY_Intel — Tue, 07 Dec 2021 10:22:07 GMT

Hi,

Could you please let us know whether you have any other issues? If not, could you please confirm whether we can close this thread from our end?

Thanks & Regards,

Santosh

Re: DCP++ subgroup

RitaChu — Tue, 07 Dec 2021 16:43:13 GMT

@SantoshY_Intel I have no more issue, please close the thread. Thank you very much

Re:DCP++ subgroup

SantoshY_Intel — Wed, 08 Dec 2021 05:36:57 GMT

Hi,

As your issue is resolved, we are closing this thread. If you need any additional information, please post a new question as this thread will no longer be monitored by Intel.

Thanks & Regards,

Santosh