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MathGroup Archive 1992

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problem with the exponential function on the NeXT

  • To: mathgroup at yoda.physics.unc.edu
  • Subject: problem with the exponential function on the NeXT
  • From: herrmann at siam.math.tamu.edu (joe herrmann)
  • Date: Sat, 26 Dec 1992 16:54:36 -0600

Dear math group,
	I found this working on my research about the energy input to cracks in  
inhomogeneous materials.  I was using Airy functions and got a strange value at one point.  
After checking Abramowitz and Stegun (p148) (10.4.59) I tried their asymptotic formula for  
the Airy function and found what was happening was a problem with the exponential  
function.  


Mathematica 2.0 for NeXT
Copyright 1988-91 Wolfram Research, Inc.

In[8]

Table[N[E^x],{x,-700000,-600000,5000}]

Out[8]
               -304007                -301835
{7.288996199 10       , 2.163103201 10       , 

 

                -299664                -297492
  6.419286457 10       , 1.905005669 10       , 

 

                -295321                -293149
  5.653348896 10       , 1.677703865 10       , 

 

            56                 -288806
  2.51105 10  , 1.4775232975 10       , 

 

                -286635                 -284463
  4.384740076 10       , 1.3012279106 10       , 

 

                -282292                 -280120
  3.861560881 10       , 1.1459677678 10       , 

 

                -277949                 -275777
  3.400806475 10       , 1.0092329824 10       , 

 

                -273606            22
  2.995028445 10       , 1.40101 10  , 

 

                -269263                -267092
  2.637667109 10       , 7.827615781 10       , 

 

                -264920                -262749
  2.322945477 10       , 6.893638932 10       , 

 

                -260577
  2.045775856 10       }


Note the incorrect results at -670,000 and -625,000.  I had a friend check this on his Sun  
and mathematica gave no incorrect answers in his test so it may only be a problem on the  
NeXT. 

Can you tell me what is happening?  Is there a fix?

Thank you.

Sincerely,

Joe Herrmann
Texas A&M Math Dept
herrmann at siam.tamu.edu






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