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