Re: Random Number Generation

[eachus@spectre.mitre.org (Robert I. Eachus)]

In article <52ten0$ish@netty.york.ac.uk> njt@minster.york.ac.uk (Nigel J. Tracey) writes:

  > Thanks for all the replies on this issue. I now have the problem
  > sorted for discrete random values. However nobody has suggested
  > a solution for generating large random reals. I really need
  > to be able to generate random values in the range of
  > Float'Safe_First..Float'Safe_Last. Or perhaps a variable
  > sub-range of these. Any idea...

  With what distribution?  If you are using this for testing
arithmetic units, I suggest unchecked converting a string of random
bits of the right length.  This will be a distribution which covers
all representable numbers equally. (To save Robert Dewar the
trouble...Certain bit patterns do not correspond to legal floating
point values.  This a legitimate use for 'VALID).  However if you want
a numerically uniform distribution:

   2.0 * Float'Safe_Last * (Ada.Numerics.Float_Random.Random(Gen) - 0.5);

   Actually you may want to add more bits to the typical floating
point generator value.


--

					Robert I. Eachus

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