Provided by: opencl-1.2-man-doc_1.0~svn22836-1.1_all 
NAME
Explicit_conversions_with_convert_T() - Explicit type conversions using convert_T()
convert_destType(sourceType) destType
convert_destType<_sat><roundingMode>
(sourceType) destTypen
convert_destTypen<_sat><roundingMode>
(sourceType)
DESCRIPTION
Explicit conversions may be performed using the convert_destType(sourceType) suite of
functions. These provide a full set of type conversions between supported types (see
scalarDataTypes(3clc)) except for the following types: bool, half, size_t, ptrdiff_t,
intptr_t, uintptr_t, and void.
The number of elements in the source and destination vectors must match.
The behavior of the conversion may be modified by one or two optional modifiers that
specify saturation for out-of-range inputs and rounding behavior.
The full form of the scalar convert function is:
destType
convert_destType<_sat><_roundingMode>(sourceType)
The full form of the vector convert function is:
destTypen
convert_destTypen<_sat><_roundingMode>(sourceTypen)
Conversions are available for the following scalar types: char, uchar, short, ushort, int,
uint, long, ulong, float, and built-in vector types derived therefrom. The operand and
result type must have the same number of elements. The operand and result type may be the
same type in which case the conversion has no effect on the type or value of an
expression.
Conversions between integer types follow the conversion rules specified in sections
6.3.1.1 and 6.3.1.3 of the C99 specification except for out-of-range behavior and
saturated conversions which are described in section 6.2.3.3 below. Rounding Modes.PP
Conversions to and from floating-point type shall conform to IEEE-754 rounding rules.
Conversions may have an optional rounding mode modifier described in the table below.
┌─────────────────────────────┬──────────────────────────────────┐
│Modifier │ Rounding Mode Description │
├─────────────────────────────┼──────────────────────────────────┤
│ │ │
│ _rte │ Round to nearest even │
├─────────────────────────────┼──────────────────────────────────┤
│ │ │
│ _rtz │ Round towards zero │
├─────────────────────────────┼──────────────────────────────────┤
│ │ │
│ _rtp │ Round toward positive │
│ │ infinity │
├─────────────────────────────┼──────────────────────────────────┤
│ │ │
│ _rtn │ Round toward negative │
│ │ infinity │
├─────────────────────────────┼──────────────────────────────────┤
│ │ │
│ no modifier specified │ Use the default rounding │
│ │ mode for this destination │
│ │ type, _rtz for conversion │
│ │ to integers or the │
│ │ default rounding mode for │
│ │ conversion to │
│ │ floating-point types. │
└─────────────────────────────┴──────────────────────────────────┘
By default, conversions to integer type use the _rtz (round toward zero) rounding mode and
conversions to floating-point type use the default rounding mode. The only default
floating-point rounding mode supported is round to nearest even, i.e the default rounding
mode will be _rte for floating-point types.
For conversions to floating-point format, when a finite source value exceeds the maximum
representable finite floating-point destination value, the rounding mode will affect
whether the result is the maximum finite floating point value or infinity of same sign as
the source value, per IEEE-754 rules for rounding.
Out-of-Range Behavior and Saturated Conversions
When the conversion operand is either greater than the greatest representable destination
value or less than the least representable destination value, it is said to be
out-of-range. The result of out-of-range conversion is determined by the conversion rules
specified by the C99 specification in section 6.3. When converting from a floating-point
type to integer type, the behavior is implementation-defined.
Conversions to integer type may opt to convert using the optional saturated mode by
appending the _sat modifier to the conversion function name. When in saturated mode,
values that are outside the representable range shall clamp to the nearest representable
value in the destination format. (NaN should be converted to 0).
Conversions to floating-point type shall conform to IEEE-754 rounding rules. The _sat
modifier may not be used for conversions to floating-point formats.
Examples
In the following example, convert_int4 converts a uchar4 vector u to an int4 vector c:
uchar4 u; int4 c = convert_int4(u);
In the following example, convert_int converts a float scalar f to an int scalar i:
float f; int i = convert_int(f);
Example:
short4 s;
// negative values clamped to 0 ushort4 u =
convert_ushort4_sat( s );
// values > CHAR_MAX converted to CHAR_MAX //
values < CHAR_MIN converted to CHAR_MIN char4 c
= convert_char4_sat( s );
Example:
float4 f;
// values implementation defined for // f >
INT_MAX, f < INT_MIN or NaN int4 i =
convert_int4( f );
// values > INT_MAX clamp to INT_MAX, values <
INT_MIN clamp // to INT_MIN. NaN should produce
0.
// The _rtz rounding mode is // used to produce
the integer values. int4 i2 =
convert_int4_sat( f );
// similar to convert_int4, except that //
floating-point values are rounded to the nearest
// integer instead of truncated int4 i3 =
convert_int4_rte( f );
// similar to convert_int4_sat, except that //
floating-point values are rounded to the //
nearest integer instead of truncated int4 i4 =
convert_int4_sat_rte( f );
Example:
int4 i;
// convert ints to floats using the default
rounding mode. float4 f = convert_float4( i );
// convert ints to floats. integer values that
cannot // be exactly represented as floats
should round up to the // next representable
float. float4 f = convert_float4_rtp( i );
SPECIFICATION
OpenCL Specification[1]
SEE ALSO
scalarDataTypes(3clc), vectorDataTypes(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 207, section 6.2.3 - Explicit Conversions