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Weird NMinimize behaviour

  • To: mathgroup at smc.vnet.net
  • Subject: [mg97518] Weird NMinimize behaviour
  • From: Filippo Miatto <miatto at gmail.com>
  • Date: Sat, 14 Mar 2009 18:13:15 -0500 (EST)

Dear all,
i'm working in the quantum optics group of the university of Leiden, 
and i use mathematica 7 a lot.
we have both windows machines and macs. On a mac i was trying to 
minimize the function

j[s_] := Sum[F2[n1, k1, n2, k2], {n1, 0, 2 s - 1}, {k1, 0, 2 s - 1}, 
{n2, 0,2s - 1}, {k2, 0, 2s - 1}] + R2[s]

Where
R2[s_] := (1 - 1/=CF=80 Sum[(-1)^(n1 + 1) Subscript[z, n1], {n1, 1, 2 s - 
1}])^4

and
F2[n1_, k1_, n2_, k2_] := (-1)^(n1 + k1 + n2 + k2)/(360 =CF=80^4) (8 =CF=80^4 - 
60 =CF=80^2 Mod[-Subscript[z, k1] + Subscript[z, n1] - Subscript[z, k2] + 
Subscript[z, n2], 2 =CF=80]^2 + 60 =CF=80 Mod[-Subscript[z, k1] + Subscript[z, 
n1] - Subscript[z, k2] + Subscript[z, n2], 2 =CF=80]^3 -15 Mod[-
Subscript[z, k1] + Subscript[z, n1] - Subscript[z, k2] +  Subscript[z, 
n2], 2 =CF=80]^4)

(sorry for the mess, on the screen the subscripts simply appear as 
subscripts...)

and i get certain results for s=1,2,3,4,5,etc..
on the windows machine though, i get worse results! the version of 
mathematica is the same, machineprecision value is the same, even 
the .nb file is the same! (the processor is different: a dualcore2duo 
on the mac and a quad core xeon on the windows machine)
The mac can work well until s=6, the windows machine can go on to 
greater values, but still giving less good results.
Do you have any idea how i can solve this issue?
Thank you in advance!
Filippo=


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