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 Scalar Data Types) 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 outofrange 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 builtin 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 outofrange behavior and saturated conversions which are described in section 6.2.3.3 below.
Conversions to and from floatingpoint type shall conform to IEEE754 rounding rules. Conversions may have an optional rounding mode modifier described in the table below.
Modifier  Rounding Mode Description 


Round to nearest even 

Round towards zero 

Round toward positive infinity 

Round toward negative infinity 
no modifier specified 
Use the default rounding mode for this destination type, 
By default, conversions to integer type use the _rtz
(round toward zero) rounding mode and conversions to floatingpoint type use the default rounding mode.
The only default floatingpoint rounding mode supported is round to nearest even, i.e the default rounding mode will be _rte
for floatingpoint types.
For conversions to floatingpoint format, when a finite source value exceeds the maximum representable finite floatingpoint 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 IEEE754 rules for rounding.
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 outofrange. The result of outofrange conversion is determined by the conversion rules specified by the C99 specification in section 6.3. When converting from a floatingpoint type to integer type, the behavior is implementationdefined.
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 floatingpoint type shall conform to IEEE754 rounding rules.
The _sat
modifier may not be used for conversions to floatingpoint formats.
Notes
OpenCL provides convert_
operators for conversion between all types.
C99 does not define what happens when a floatingpoint type is converted to integer type and the floatingpoint value lies outside the representable range of the integer type after rounding.
When the sat
variant of the conversion is used, the float shall be converted to the nearest representable integer value.
Similarly, OpenCL also makes recommendations about what should happen with NaN.
Hardware manufacturers that provide the saturated conversion in hardware may use the saturated conversion hardware for both the saturated and nonsaturated versions of the OpenCL convert
operator.
OpenCL does not define what happens for the nonsaturated conversions when floatingpoint operands are outside the range representable integers after rounding.
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 // floatingpoint values are rounded to the nearest // integer instead of truncated int4 i3 = convert_int4_rte( f ); // similar to convert_int4_sat, except that // floatingpoint 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 );