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 floating-point vector | cl_half2 |
| half3 | 3-component half-precision floating-point vector | cl_half3 |
| half4 | 4-component half-precision floating-point vector | cl_half4 |
| half8 | 8-component half-precision floating-point vector | cl_half8 |
| half16 | 16-component half-precision floating-point vector | cl_half16 |
The relational, equality, logical and logical unary
operators 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 for an
OpenCL device that supports half precision floating-point.
Conversions
The implicit conversion rules specified in section 6.2.1
now include the half scalar and
halfn
vector data types.
The explicit casts described in section 6.2.2 are
extended to take a half scalar data type and a
halfn vector data type.
The explicit conversion functions described in section
6.2.3 are extended to take a half scalar
data type and a halfn
vector data type.
The as_typen()
function for re-interpreting types as described in section
6.2.4.2 is extended to allow conversion-free casts between
shortn,
ushortn and
halfn
scalar and vector data types.
Also see
EXTENSION, clGetDeviceInfo, mathFunctions, commonFunctions, geometricFunctions, relationalFunctions, vectorDataLoadandStoreFunctions, asyncCopyFunctions, imageFunctions
Copyright © 2007-2013 The Khronos Group Inc.
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