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[anu9anna]

Hi ,

              Can anyone explain whether opencl1.2 supports double precision? I understand that this is optional for 1.2 . If so how to enable the support?

Thanks

[ankhster]

Yes, OpenCL 1.2 supports double precision. Whether or not your device does is another question.

You can query your device to test this.

Page 39 onwards of the OpenCL 1.2 Specification: www.khronos.org/registry/cl/specs/opencl-1.2.pdf

If double precision is not supported, CL_DEVICE_PREFERRED_VECTOR_WIDTH_DOUBLE must return 0.

If double precision is not supported, CL_DEVICE_NATIVE_VECTOR_WIDTH_DOUBLE must return 0.

[anu9anna]

Thanku ankhster .. Can you just tell me if the device supports double precision, what should be the value ?

[ankhster]

As it says, the device must return zero if the device does not support double precision. Depending on the device you will get a zero or non-zero answer.

The values I get are:

Preferred Double Vector Width    1    // This is HD 7970 GPU

Preferred Double Vector Width    2    // This is Intel Q9450 CPU

indicating both devices support double precision.

[anu9anna]

I tried to get the info from the device Intel(R) Core(TM)2 Duo CPU E7500 and I got both the values as zero.

So does it mean that the CPU doesn't support double precision. Then how can I use double precision algorithms??

[nou]

you should check for cl_khr_fp64 device extension.

[anu9anna]

can I check using clinfo?

[ankhster]

Indeed you can, you should get something like this:

        CL_DEVICE_EXTENSIONS:   cl_khr_fp64 cl_amd_fp64 cl_khr_global_int32_base_atomics cl_khr_global_int32_extended_atomics cl_khr_local_int32_base_atomics cl_khr_local_int32_extended_atomics cl_khr_int64_base_atomics cl_khr_int64_extended_atomics cl_khr_3d_image_writes cl_khr_byte_addressable_store cl_khr_gl_sharing cl_ext_atomic_counters_32 cl_amd_device_attribute_query cl_amd_vec3 cl_amd_printf cl_amd_media_ops cl_amd_popcnt cl_khr_d3d10_sharing cl_khr_dx9_media_sharing

[anu9anna]

Hi,

         Do we have any other API to read and write data from and to the device other than , clEnqueueReadBuffer and clEnqueueWriteBuffer ?

[nou]

clEnqueueMapBuffer()