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MathGroup Archive 1992

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Re: problem with the exponential function on the NeXT

  • To: mathgroup at yoda.physics.unc.edu
  • Subject: Re: problem with the exponential function on the NeXT
  • From: me at leidecker.gsfc.nasa.gov
  • Date: Tue, 29 Dec 92 09:52:00 -0500

Joe Herrmann writes that he used his NeXT and Mma to evaluate 

Table[N[E^x],{x,-700000,-600000,5000}], and then found *wrong* results  
for x=-670,000 and x=-625,000.  However, correct results were observed  
when running on a friend's Sun.

I just evaluated the expression on my NeXT, and did not get the reported  
wrong values --- all of them looked fine.  And my friend, Charles Powers,  
just ran the full expression on his NeXT --- all the values look fine.   
In particular, we both get E^(-670,000)=4.97880161*10^(-290978). (Other  
values supplied on request.)

I am running Mma ver. 1.2 (I'll get around to upgrading someday) on a  
Cube with the 25 MHz 040 board, and NeXTstep 3.0; and Powers is running  
Mma ver. 2.1 on a NeXTstation with a 33 MHz 040, and NeXTstep 3.0.

NeXTstep 2.0 had a bug in the routines that the 040's internal math  
co-processor used to handle the transcendentals --- perhaps Joe found  
something like that?

Regards,
Henning Leidecker





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