Provided by: opencl-1.2-man-doc_1.0~svn33624-1_all 
NAME
cl_khr_fp16 - Optional half floating-point support.
#pragma OPENCL EXTENSION cl_khr_fp16 : enable
DESCRIPTION
This extension adds support for half scalar and vector types as built-in types that can be used for
arithmetic operations, conversions, etc. An application that wants to use half and halfn types will need
to include the directive shown above.
The list of built-in scalar and vector data types are extended to include the types in the table below.
The built-in vector data types for halfn are also declared as appropriate types in the OpenCL API (and
header files) that can be used by an application. The following table describes the built-in vector data
types for halfn as defined in the OpenCL C programming language and the corresponding data type available
to the application:
┌────────────────────────┬─────────────────────────────┬──────────────────────────┐
│Type in OpenCL Language │ Description │ API type for application │
├────────────────────────┼─────────────────────────────┼──────────────────────────┤
│half2 │ 2-component half-precision │ cl_half2 │
│ │ floating-point vector │ │
├────────────────────────┼─────────────────────────────┼──────────────────────────┤
│half3 │ 3-component half-precision │ cl_half3 │
│ │ floating-point vector │ │
├────────────────────────┼─────────────────────────────┼──────────────────────────┤
│half4 │ 4-component half-precision │ cl_half4 │
│ │ floating-point vector │ │
├────────────────────────┼─────────────────────────────┼──────────────────────────┤
│half8 │ 8-component half-precision │ cl_half8 │
│ │ floating-point vector │ │
├────────────────────────┼─────────────────────────────┼──────────────────────────┤
│half16 │ 16-component half-precision │ cl_half16 │
│ │ floating-point vector │ │
└────────────────────────┴─────────────────────────────┴──────────────────────────┘
The relational, equality, logical and logical unary operators(3clc) can be used with half scalar and
halfn vector types and shall produce a scalar int and vector shortn result respectively.
The OpenCL compiler accepts an h and H suffix on floating point literals, indicating the literal is typed
as a half.
The macro names given in the following list must use the values specified. These constant expressions are
suitable for use in #if preprocessing directives.
The following table also describes the corresponding macro names available to the application.
Macro in OpenCL Language value Macro for application
#define HALF_DIG 3 HALF_DIG
#define HALF_MANT_DIG 11 HALF_MANT_DIG
#define HALF_MAX_10_EXP +4 HALF_MAX_10_EXP
#define HALF_MAX_EXP +16 HALF_MAX_EXP
#define HALF_MIN_10_EXP -4 HALF_MIN_10_EXP
#define HALF_MIN_EXP -13 HALF_MIN_EXP
#define HALF_RADIX 2 HALF_RADIX
#define HALF_MAX 0x1.ffcp15h HALF_MAX
#define HALF_MIN 0x1.0p-14h HALF_MIN
#define HALF_EPSILON 0x1.0p-10h HALF_EPSILON
The following constants are also available. They are of type half and are accurate within the precision
of the half type.
┌─────────────┬──────────────────┐
│Constant │ Description │
├─────────────┼──────────────────┤
│M_E_H │ Value of e │
├─────────────┼──────────────────┤
│M_LOG2E_H │ Value of log2 e │
├─────────────┼──────────────────┤
│M_LOG10E_H │ Value of log10 e │
├─────────────┼──────────────────┤
│M_LN2_H │ Value of ln 2 │
├─────────────┼──────────────────┤
│M_LN10_H │ Value of ln 10 │
├─────────────┼──────────────────┤
│M_PI_H │ Value of π │
├─────────────┼──────────────────┤
│M_PI_2_H │ Value of π / 2 │
├─────────────┼──────────────────┤
│M_PI_4_H │ Value of π / 4 │
├─────────────┼──────────────────┤
│M_1_PI_H │ Value of 1 / π │
├─────────────┼──────────────────┤
│M_2_PI_H │ Value of 2 / π │
├─────────────┼──────────────────┤
│M_2_SQRTPI_H │ Value of 2 / √π │
├─────────────┼──────────────────┤
│M_SQRT2_H │ Value of √2 │
├─────────────┼──────────────────┤
│M_SQRT1_2_H │ Value of 1 / √2 │
└─────────────┴──────────────────┘
Ann application may query the configuration information using the op-code CL_DEVICE_HALF_FP_CONFIG with
clGetDeviceInfo(3clc) for an OpenCL device that supports half precision floating-point.
SPECIFICATION
OpenCL Specification[1]
SEE ALSO
EXTENSION(3clc), clGetDeviceInfo(3clc), mathFunctions(3clc), commonFunctions(3clc),
geometricFunctions(3clc), relationalFunctions(3clc), vectorDataLoadandStoreFunctions(3clc),
asyncCopyFunctions(3clc), imageFunctions(3clc)
AUTHORS
The Khronos Group
COPYRIGHT
Copyright © 2007-2011 The Khronos Group Inc.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or
associated documentation files (the "Materials"), to deal in the Materials without restriction, including
without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to
the condition that this copyright notice and permission notice shall be included in all copies or
substantial portions of the Materials.
NOTES
1. OpenCL Specification
page 14, section 9.5 - Half Floating-Point