On Sep 28, 2009, at 9:40 AM, Olex P wrote:
Hi,
Yes, I mean "sizeOf 2". It's useful not only on GPUs but also in
"normal" software. Think of huge data sets in computer graphics
(particle clouds, volumetric data, images etc.) Some data (normals,
density, temperature and so on) can be easily represented as float
16 making files 200 GB instead of 300 GB. Good benefits.
From the OpenEXR technical introduction:
half numbers have 1 sign bit, 5 exponent bits,
and 10 mantissa bits. The interpretation of
the sign, exponent and mantissa is analogous
to IEEE-754 floating-point numbers. half
supports normalized and denormalized numbers,
infinities and NANs (Not A Number). The range
of representable numbers is roughly 6.0E-8 to 6.5E4;
numbers smaller than 6.1E-5 are denormalized.
Single-precision floats are already dangerously short for
many computations. (Oh the dear old B6700 with 39 bits of
precision in single-precision floats...) Half-precision
floats actually have less than half the precision of singles
(11 bits instead of 23). It's probably best to think of
binary 16 as a form of compression for Float, and to write
stuff that will read half-precision from a binary stream as
single-precision, and conversely stuff that will accept
single-precision values and write them to a binary stream in
half-precision form.
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