Are atomics supported or not?

[peastman]

I've just begun testing my code under Intel OpenCL, and I've found what appears to be a bug. If I queryCL_DEVICE_EXTENSIONS, it returns the following:

cl_khr_fp64 cl_khr_icd cl_khr_global_int32_base_atomics cl_khr_global_int32_extended_atomics cl_khr_local_int32_base_atomics cl_khr_local_int32_extended_atomicscl_khr_byte_addressable_store cl_intel_printf cl_ext_device_fission cl_intel_exec_by_local_thread cl_khr_gl_sharing cl_intel_dx9_media_sharing

Notice the third one listed:cl_khr_global_int32_base_atomics. But when I try to compile a kernel that uses that extension, it gives the following warning:

:9:61: warning: OpenCL extension 'cl_khr_global_int32_base_atomics' is not supported - ignoring

So is it really supported or not? This is on Windows 7, with an Ivy Bridge processor and using the CPU device.

Peter

[Brijender_B_Intel]

Hi,
which device are you checking for - CPU or HD4000?

Just curious, do you have a usecase to use global atomics? I have not seen many people using it.
thanks

[peastman]

It's on the CPU. Yes, I use global atomics extensively.

Peter

[Raghupathi_M_Intel]

Hi Peter,

What driver version and SDK are you using. Using the latest SDK and driver (both internal)I couldnt reproduce the warning.

Thanks,
Raghu

[peastman]

The graphics driver is 8.15.10.2696. The SDK version is 2.0.

Peter

[peastman]

Do any Intel engineers read this forum? Is there a better place to ask questions?

Peter

[Raghupathi_M_Intel]

Sorry for the delay in responding. Our engineers were buried in other tasks.

I found out that we do support atomics but I am trying to find out why the warning is generated. Other than the warning do you see incorrect behavior using atomics?

Thanks,
Raghu

[peastman]

Thanks. Aside from the warning, it appears to be working.

Peter

[Guy_B_Intel]

Hi Peter,
Sorry again for the delay.
This atomic extension became a core feature since OpenCL 1.1, and that's why you do not need to use the extension pragma on our product, whichcomplies with theOpenCL 1.1 specification.

Thanks,
Guy Benyei

[EvgeniyPeshkov]

HiGuy,

Sorry, but in my opinion it doesn't solve the problem with generated warnings. According to OpenCL 1.1 specification this atomic extensions must be supported by all devices that support OpenCL 1.1 C to provide backwardscompatibility. In other case you can not use programs written in OpenCL 1.0 C using extentions that became a core features in later versions of OpenCL. So it'sdeviation from standard.

By the way enablingcl_intel_printf extension causes warning too. See this thread for more informationhttp://software.intel.com/en-us/forums/showthread.php?t=106028