Re: Calculation issue with octave (data unexpectedly go to zero at some point)

[rchretien]

Thank you all for your answers.

I understand you better Michael. I have found back a much (much !) simpler
version of the code, exhibiting the same problem with octave, dating of last
September, so that it should be simple to launch. Please, find that version
here :

https://www.dropbox.com/sh/hiuv8u4jxqk2hs3/tI_GfBHJ3Y

Simply uncompress the archive, composed of a minimalistic version of the
code. To launch it, use the function called main that way :

[expectedPopulationOfGroundState] = main(N)

where N is a parameter denoting the number of realisations of the method (I
suggest to put N=1, since the problem does not depend on N).

Then, look at what happens when launched under Octave :


> expectedPopulationOfGroundState =
> 
>    0.00000
>    0.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    1.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000
>    0.00000 

And what happens when launched under matlab


> expectedPopulationOfGroundState =
> 
>     0.0000
>          0
>          0
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000
>     1.0000

Since the problem treated here is the spontaneous emission of a photon by an
atom, the expected population of the ground state is expected to be one when
the time is large (this explanation is given just in case someone tries to
understand the code).

Bill, I have read your answer and I am going to test tomorrow since I am
running out of time tonight. I will provide more details tomorrow if
necessary.

Once again, thank you for your help.

Best regards,

Renaud



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