[Haskell-cafe] 16 bit floating point data in Haskell?
Richard O'Keefe
ok at cs.otago.ac.nz
Sun Sep 27 19:06:47 EDT 2009
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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