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Editorial Team
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Asked: 2026-06-03T15:55:02+00:00

Does anybody know the state of half precision floating point support in OpenCL as

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Does anybody know the state of half precision floating point support in OpenCL as implemented by Apple.

According to http://www.khronos.org/registry/cl/sdk/1.2/docs/man/xhtml/cl_khr_fp16.html

#pragma OPENCL EXTENSION cl_khr_fp16 : enable

should enable support for types such as half4 but when I come to build the kernel the compiler throws a message such as

error: variable has incomplete type 'half4' (aka 'struct __Reserved_Name__Do_not_use_half4')

is there anyway I can have half4 support in Apple’s OpenCL?

Thanks.

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1 Answer

  1. Editorial Team

    The cl_khr_fp16 extension (floating point operations on the 16bit scalar type (half) and vectors of half (half2,half3,half4,half8,half16) is an optional extension to OpenCL 1.0, 1.1 and 1.2.

    An OpenCL extension defines a macro of the same name as the extension if it is supported in the OpenCL implementation.

    e.g.

    #ifdef cl_khr_fp16
#pragma OPENCL EXTENSION cl_khr_fp16 : enable
... // Code using half
#else
#error No FP16 support
#endif

    I do not believe Apple are shipping an OpenCL with half support.

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