Different Results with Different Operating systems

[faraklit]

Hi,
I have been working with OpenSees for three years.
I have just noticed that OpenSees gives different results with different computers; one is windows 7 and other is Ubuntu 14.04. The code is totally same, however; the result is different. Is this normal? Or there is problem with my computers.

[fmk]

i can give you 2 exe for the same os that will give different results by changing the optimization flags sent to the compiler .. while the source code is the same the set of instructions generated by the compiler is different .. as a consequence of this and the fact that we deal in finite precision mathematics when running on a computer, the results start getting different .. typically not noticable unless you start looking at the last digits .. it can be noticable if problems start becoming ill-conditioned and small changes on rhs of the matrix equation lead to big changes in solution .. excaserbated if transient problems, for if you consider some step during the analysis as starting point and boundary condition at that step are different which will result in a different end solution.