What do codes do in Diffpy_CMI?

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ali dordaee

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Aug 1, 2021, 7:30:16 PMAug 1
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Dear all, 
 Sorry if my questions look rudimentary. I have three questions:
 1. What is Scipy's LM optimizer matematically and where can I find the mathematical equations for it, if you know a good book I'd really appreciate it. Is it different than Scipy's least-squares method?

 2. The source codes in Github for Diffpy-CMI seem a little vague for me. What I mean is they definitely have used some mathematical equations, that's why they are working fine. I think those equations and algorithms can not be found in the GitHub page. To be more specific, I need to know how EXACTLY and MATHEMATICALLY diffpy-cmi calculates and obtains different parameters(like lattice parameter, particle size, ADP's, etc.). All I know is it definitely uses an iterative method, but if there is an in-situ example or an example which lets us follow through the process step by step(like an slow-motion movie), I'd really appreciate it if you could please introduce it to me. All I need is to know the iterative processes that are going on here.
 
 3. There are some functions in diffpy-cmi, like Fitrecipe() or PDFcontribution(), Profile(), PDFParser(), etc. which are still a little bit unclear for me. Can I find what exactly they are in somewhere? When I want to use "addVar" function, we know it already containts some parameters like scale, delta's, qdamp, etc. I searched to see what exactly is there inside "addVar" in Github, but it is like a vicious circle, one code refers to the other and that one refers to the first one without saying what exactly and mathematically they are doing.

 I hope I could let you know what is going on in my mind and thanks in advance for your time and consideration.

 Any help or guidance would be highly appreciated. 
 Thanks.
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