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Operations Research Software Development Mathematica

Posted 12 years ago

My augmented Lagrangian local minimization code gives slightly different results for the same inputs for a problem involving packing 50 integer circles. Past work has shown that circle packing is chaotic in that slightly different inputs give different results but I don't understand why the same input gives different results. For the first run, I get an objective function value of 232.568 and 232.132 for the second. The starting point is generated randomly but is used for both runs. The attached notebook has the code. It was run with Mathematica Version 10.1 on a PC running Windows 8. Attachments:

POSTED BY: Frank Kampas

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Posted 12 years ago

I put in some Print statements. The results of the first FindMinimum run are different when the final results differ.

POSTED BY: Frank Kampas

Posted 12 years ago

Well, my impression of Windows 8 is that your results might depend on what's currently available on Taylor Swift's facebook page. ;-)

POSTED BY: David Keith

Posted 12 years ago

I also get the same result both times under Win 7 x64.

POSTED BY: Frank Kampas

Posted 12 years ago

The problem does not occur on my MacBookAir, which makes me think it is not a coding problem but a problem related to the operating system. When I run packing problems with MathOptimizer Professional, which compiles the objective function and and constraints to Fortran or C, I get slightly different results with different compilers, but consistent results for one compiler.