Mac FixedPoint[] problem looks like SameQ[] is culprit
- To: mathgroup at smc.vnet.net
- Subject: [mg119543] Mac FixedPoint[] problem looks like SameQ[] is culprit
- From: "McHale, Paul" <Paul.McHale at excelitas.com>
- Date: Wed, 8 Jun 2011 07:15:42 -0400 (EDT)
If this has already been covered, I apologize for the redundancy. I was playing with the problem with a Mac and PC side by side. The first test was to limit the iterations to see if the algorithm was working at all by running the following on the Mac.
m=Table[FixedPoint[Cos,1.1,x],{x,75,85}]
Table[{i+74,m[[i]]==m[[i+1]]},{i,1,Length[m]-1}]
{0.739085,0.739085,0.739085,0.739085,0.739085,0.739085,0.739085,0.739085,0.739085,0.739085,0.739085}
{{75,False},{76,False},{77,False},{78,False},{79,False},{80,False},{81,True},{82,True},{83,True},{84,True}}
This was the same on the PC. So it appeared the algorithm worked if I killed at iteration X. I started playing with the verification that is used to determine whether to re-apply the function.
FixedPoint[Cos,1.1,SameTest-> (#1 == #2&)]
0.739085
FixedPoint[Cos,1.1,SameTest->(Abs[#1-#2]<1*^-10&)]
0.739085
FixedPoint[Cos,1.1,SameTest->(Equal[#1,#2]&)]
0.739085
FixedPoint[Cos,1.1,SameTest->(SameQ[#1,#2]&)]
$Aborted
My conclusion is SameQ has some issue. Anyone think this is correct? BTW, all work on the PC.
Thanks,
Paul
Paul McHale | Electrical Engineer, Energetics Systems | Excelitas Technologies Corp.
Phone: +1 937.865.3004 | Fax: +1 937.865.5170 | Mobile: +1 937.371.2828
1100 Vanguard Blvd, Miamisburg, Ohio 45342-0312 USA
Paul.McHale at Excelitas.com
www.excelitas.com
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