Name

log2 - returns the base-2 logarithm of scalars and vectors

Synopsis

float  log2(float a);
float1 log2(float1 a);
float2 log2(float2 a);
float3 log2(float3 a);
float4 log2(float4 a);

half   log2(half a);
half1  log2(half1 a);
half2  log2(half2 a);
half3  log2(half3 a);
half4  log2(half4 a);

fixed  log2(fixed a);
fixed1 log2(fixed1 a);
fixed2 log2(fixed2 a);
fixed3 log2(fixed3 a);
fixed4 log2(fixed4 a);

Parameters

a

Vector or scalar of which to determine the base-2 logarithm.

Description

Returns the base-2 logarithm a.

For vectors, the returned vector contains the base-2 logarithm of each element of the input vector.

Reference Implementation

float3 log2(float3 a)
{
  float3 rv;
  int i;

  for (i=0; i<3; i++) {
    rv[i] = log2(a[i]);  // this is the ANSI C standard library log2()
  }
  return rv;
}

log2 is typically implemented with a native base-2 logarithm instruction.

Profile Support

log2 is fully supported in all profiles unless otherwise specified.

Support in the fp20 is limited to constant compile-time evaluation.

See Also

exp, log, log10, pow