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Old   August 14, 2007, 09:33
Default Relative error
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Hi all,

I've got a question related to relative errors in the special case where the x(exact) is nearly 0.

Example : x(exact) = 1 e-10 x(simul) = 0.001

Er = |x(exact)-x(simul)|/|x(exact)| = 9999999!!!

I would like to know if there is a way to avoid this situation.

Thanks in advance.
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Old   August 14, 2007, 11:39
Default Re: Relative error
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Can you make your system non dimensional ? In that way you would not need to go for such high precision requirements.
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Old   August 14, 2007, 11:55
Default Re: Relative error
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Well, the purpose is to compare some methods via the absolute and relative errors. The equation resolved is of type: m.d2(y)/dt2 + k.y = f with y=1 and dy/dt=0 and the exact solution is y=cos(wt). It's clear to see that the y is zero, or nearly, at Pi/2 for example, as I explained before.

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