bandwidth of different clImage format and efficient access pattern

[chris_pn]

Hi,

    Per OpenCL Developer Guide (as shown below), I find that max bandwidth of each sampler is 64 Byte/cyc:

https://software.intel.com/content/www/us/en/develop/documentation/iocl-opg/top/coding-for-the-intel-processor-graphics/memory-hierarchy.html

    My questions are:

1. Which clImage format with (efficient access pattern) can achieve max bandwidth?

2. Does different clImage format has a max texel/cyc when read by sampler? If yes, where can I find the data for common-used format?

3. What's efficient access pattern to read clImage by Sampler?

    Thanks!

[VidyalathaB_Intel]

Hi Chris,

Thanks for reaching out to us

we are working on your issue. we will get back to you soon

Regards,

Vidya

[chris_pn]

Thanks Vidya. For clImage write operation, I also has the same question. So many thanks If you could also provide answer for clImage write operation. Thanks again!

[chris_pn]

Hi Vidya,

    Can you answer my questions now or could you tell me how long should I wait for the answer? Thanks.

[chris_pn]

Hi Vidya,

    Do you have any update? I'm looking forward to your answer. Thanks!

[Dunni_A_Intel · Accepted solution]

Hi Chris,

Apologies for the delay in providing you with a timely response.

1. The maximum bandwidth may only be achieved when all accesses hit the cache. In general, accesses to smaller image formats will yield better performance than accesses to larger image formats.
2. Yes, performance varies with different image formats. However, I am unable to locate any public documents with specific performance numbers.
3. 2D accesses patterns will be efficient based on how images are actually laid out in memory.

Please let me know if this answers your questions and if you have any additional questions.

[chris_pn]

Hi Dunni,

    Thanks for your answer. It can be better if there is detailed explaination and samples. Current answer related to clImage provided by Intel official document is too short and rough to understand. Image is also a important memory object of OpenCL for user. Thanks anyway.

[Dunni_A_Intel]

Hi Chris,

We will no longer be monitoring this thread. Please feel free to make a new post if you have additional questions.