Provided by: opencl-1.2-man-doc_1.0~svn33624-5_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 │ cl_half2 │
│ │ half-precision │ │
│ │ floating-point vector │ │
├────────────────────────┼───────────────────────┼──────────────────────────┤
│half3 │ 3-component │ cl_half3 │
│ │ half-precision │ │
│ │ floating-point vector │ │
├────────────────────────┼───────────────────────┼──────────────────────────┤
│half4 │ 4-component │ cl_half4 │
│ │ half-precision │ │
│ │ floating-point vector │ │
├────────────────────────┼───────────────────────┼──────────────────────────┤
│half8 │ 8-component │ cl_half8 │
│ │ half-precision │ │
│ │ floating-point vector │ │
├────────────────────────┼───────────────────────┼──────────────────────────┤
│half16 │ 16-component │ cl_half16 │
│ │ half-precision │ │
│ │ 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