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MathGroup Archive 2008

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Re: Machine-precision Exp[] function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg93624] Re: Machine-precision Exp[] function
  • From: Roman <rschmied at gmail.com>
  • Date: Tue, 18 Nov 2008 07:22:20 -0500 (EST)
  • References: <gfma98$g54$1@smc.vnet.net>

Daniel Lichtblau kindly pointed out a very simple solution: with
  SetSystemOptions["CatchMachineUnderflow" -> False]
the default behavior of switching to arbitrary-precision numbers can
be suppressed. After the above command, we get
  In[1] := Exp[-1`*^6]
  Out[1] = 0.`
and the execution speed is identical to that of the compiled command.

There are some hints in this direction in the help file under
$MinMachineNumber, but they seem outdated (Version 6.0.2.0) as they
invoke the command
  Developer`SetSystemOption["CatchMachineUnderflow" -> False]
which no longer exists.

Roman.


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