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How to understand divergence_approx #25

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jatentaki opened this issue Apr 23, 2021 · 1 comment
Open

How to understand divergence_approx #25

jatentaki opened this issue Apr 23, 2021 · 1 comment

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@jatentaki
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I'm trying to understand divergence_approx. I am not sure what exactly it is trying to compute, I suppose something related to the trace of the Jacobian, that is equation 7 in your paper (linking in case the numbering differed between versions or something).

I am confused on two levels. Firstly, I don't know what the variables mean: the function arguments are called (f, y, e) but the function returns something called dzdx and finally it is called in a context where f=dy and y=y, so it would compute something related to d^2y/y^2?? Secondly, I don't understand the overall implementation, why is it looping (and seemingly computing the same thing in a loop, since this call is equivalent to that from line 10 and its parameters are not being updated between the iterations. Finally, why is the e parameter fixed?

Thank you in advance for your response

@emilemathieu
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Hello,

I am also wondering what is the while loop for? @stevenygd

Best,
Emile

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