fast_normalize

Normal vector length 1.

floatn fast_normalize ( floatn p)

Description

Returns a vector in the same direction as p but with a length of 1. fast_normalize is computed as:

          p * half_rsqrt(p.x2 + p.y2 +...)

The result shall be within 8192 ulps error from the infinitely precise result of:

          if (all(p == 0.0f))
                    result = p;
          else
                    result = p /  sqrt(p.x2 + p.y2 +...);

with the following exceptions:

  1. If the sum of squares is greater than FLT_MAX then the value of the floating-point values in the result vector are undefined.

  2. If the sum of squares is less than FLT_MIN then the implementation may return back p.

  3. If the device is in 'denorms are flushed to zero' mode, individual operand elements with magnitude less than sqrt(FLT_MIN) may be flushed to zero before proceeding with the calculation.

Notes

Built-in geometric functions operate component-wise. The description is per-component. floatn is float, float2, float3, or float4 and doublen is double, double2, double3, or double4. The built-in geometric functions are implemented using the round to nearest even rounding mode.

The geometric functions can be implemented using contractions such as mad or fma.

Specification

OpenCL Specification

Also see

Geometric Functions

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