StackOverflow2013

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POFloat32 to Float16
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copied!<p>Can someone explain to me how I convert a 32-bit floating point value to a 16-bit floating point value?</p> <p>(s = sign e = exponent and m = mantissa)</p> <p>If 32-bit float is 1s7e24m<br> And 16-bit float is 1s5e10m </p> <p>Then is it as simple as doing?</p> <pre><code>int fltInt32; short fltInt16; memcpy( &fltInt32, &flt, sizeof( float ) ); fltInt16 = (fltInt32 & 0x00FFFFFF) >> 14; fltInt16 |= ((fltInt32 & 0x7f000000) >> 26) << 10; fltInt16 |= ((fltInt32 & 0x80000000) >> 16); </code></pre> <p>I'm assuming it ISN'T that simple ... so can anyone tell me what you DO need to do?</p> <p>Edit: I cam see I've got my exponent shift wrong ... so would THIS be better?</p> <pre><code>fltInt16 = (fltInt32 & 0x007FFFFF) >> 13; fltInt16 |= (fltInt32 & 0x7c000000) >> 13; fltInt16 |= (fltInt32 & 0x80000000) >> 16; </code></pre> <p>I'm hoping this is correct. Apologies if I'm missing something obvious that has been said. Its almost midnight on a friday night ... so I'm not "entirely" sober ;)</p> <p>Edit 2: Ooops. Buggered it again. I want to lose the top 3 bits not the lower! So how about this:</p> <pre><code>fltInt16 = (fltInt32 & 0x007FFFFF) >> 13; fltInt16 |= (fltInt32 & 0x0f800000) >> 13; fltInt16 |= (fltInt32 & 0x80000000) >> 16; </code></pre> <p><strong>Final code should be</strong>:</p> <pre><code>fltInt16 = ((fltInt32 & 0x7fffffff) >> 13) - (0x38000000 >> 13); fltInt16 |= ((fltInt32 & 0x80000000) >> 16); </code></pre>

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