Use Built-In Functions
OpenCL™ offers a library of built-in functions, including vector variants.
For details, see the OpenCL specification.
Using built-in functions is typically more efficient than using their
manual implementation in OpenCL code. Consider the following code example:
__kernel void Foo(const __global float* a, const __global float* b, __global float* c) { int tid = get_global_id(0); c[tid] = 1/sqrt(a[tid] + b[tid]); }
The following code uses the
rsqrt
built-in to implement
the same example:__kernel void Foo(const __global float* a, const __global float* b, __global float* c) { int tid = get_global_id(0); c[tid] = rsqrt(a[tid] + b[tid]); }
Consider simple expressions and built-ins based equivalents below:
dx * fCos + dy * fSin == dot( (float2)(dx, dy),(float2)(fCos, fSin)) x * a - b == mad(x, a, -b) sqrt(dot(x, y)) == distance(x,y)
Use specialized built-in versions like
math
, integer
,
and geometric
built-ins, where possible, as the specialized
built-ins work faster than their manually-computed counterparts. For example,
when the x
value for xy
is ≥0, use powr
instead of pow
.See Also
The OpenCL™ 1.2 Specification at