OpenCL™ Developer Guide for Intel® Core™ and Intel® Xeon® Processors
Visible to Intel only — GUID: GUID-BB455275-1969-4973-A898-9896BEFA2E6E
Visible to Intel only — GUID: GUID-BB455275-1969-4973-A898-9896BEFA2E6E
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 https://www.khronos.org/registry/OpenCL/specs/opencl-1.2.pdf