[Beowulf] Re: Accelerator for data compressing

Jason Riedy jason at acm.org
Mon Oct 6 12:50:30 EDT 2008


And Greg Lindahl writes:
> I often find that floating-point data doesn't compress much, but that
> ASCII representations of the same data compresses to a file smaller
> than the binary one.

However, some care is necessary if you're using decimal output rather
than hex.  I've run into problems with the identical decimal (in ASCII)
number converting to different binary numbers.  The difference is only
in the last bit, but that ends up being important for my uses.

Sometimes the cause is an actual bug in the conversion, but most times
the decimal version provided *more* than the number of decimal digits
expected for the binary format.  For example, some people store 20
digits rather than 17 for decimal.  Different systems handle the extra
digits differently.  sigh.  And remember that 754-1985 did *not* require
correct conversion for all numbers, so some people have not provided
correct conversion.  (The new 754-2008 *does* require correct
conversion.)

But there's C99-style hex output.  Makes my life much easier.  And
conversions are relatively fast, unlike the conversions to/from decimal.

Jason
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