  
    <bridgehead>Half and Native forms</bridgehead>

    <para>
        A subset of Math functions (table 6.8) are defined 
        with the <code>half_</code> prefix. These 
        functions are implemented with a minimum of 
        10-bits of accuracy i.e. an ULP value &le; 
        8192 ulp.
    </para>

    <para>
        A subset of Math functions (table 6.8) are 
        defined with the <code>native_</code> prefix. These 
        functions may map to one or more native device 
        instructions and will typically have 
        better performance compared to the corresponding 
        functions (without the <code>native__</code>
        prefix). The accuracy (and in some cases the 
        input range(s)) of 
        these functions is implementation-defined.
    </para>

    <para>
        For the half and native forms, we use the 
        generic type name 
        gentype to indicate that the functions 
        (table 6.9) can take 
        <type>float</type>, <type>float2</type>, 
        <type>float3</type>, 
        <type>float4</type>, <type>float8</type> 
        or <type>float16</type> as the type for the 
        arguments.
    </para>

    <para>
        Support for denormal values is optional for 
        <code>half_</code> functions. The <code>half_</code> 
        functions may return any 
        result allowed by section 7.5.3, even when 
        <code>-cl-denorms-are-zero</code> (see section 5.8.4.2) is not in 
        force. Support for denormal values is 
        implementation-defined for <code>native_</code> functions.
    </para>

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