# Description of a method in Minpack

**URL:** <https://fortran-lang.discourse.group/t/description-of-a-method-in-minpack/7314>\
**Category:** Help\
**Created:** [February 2, 2024, 6:09am UTC](https://fortran-lang.discourse.group/t/description-of-a-method-in-minpack/7314 "2024-02-02T06:09:31Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![nicholaswogan](https://avatars.discourse-cdn.com/v4/letter/n/f1d935/32.png) [@nicholaswogan](https://fortran-lang.discourse.group/u/nicholaswogan)\
**Post date:** [February 2, 2024, 6:09am UTC](https://fortran-lang.discourse.group/t/description-of-a-method-in-minpack/7314/1 "2024-02-02T06:09:31Z")

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The Github page for modern Minpack () provides the following citation for the non-linear solver (`hybrd`) in the package:

> - M. J. D. Powell, A Hybrid Method for Nonlinear Equations. Numerical Methods for Nonlinear Algebraic Equations, P. Rabinowitz, editor. Gordon and Breach, 1970.

But I can’t find the article anywhere (my universities library, google, etc.). Does anyone know of where I can find a good description of Powell’s hybrid method for nonlinear equations?

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**Author:** ![gak](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/gak/32/146_2.png) [@gak](https://fortran-lang.discourse.group/u/gak)\
**Post date:** [February 2, 2024, 7:29am UTC](https://fortran-lang.discourse.group/t/description-of-a-method-in-minpack/7314/2 "2024-02-02T07:29:45Z")

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I found a copy on The Internet Archive, available to be borrowed.

[A Hybrid Method for Nonlinear Equations by M. J. D. Powell](https://openlibrary.org/books/OL4766575M/Numerical_methods_for_nonlinear_algebraic_equations)

I have a rather hefty PDF of the article (pages 87-114); email me if you would like a copy of it.

Also this [Mathematica implementation](https://cosmos.phy.tufts.edu/Powell/).

And this Handwiki article on [Powell’s dog leg method](https://handwiki.org/wiki/Powell%27s_dog_leg_method).

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**Author:** ![nicholaswogan](https://avatars.discourse-cdn.com/v4/letter/n/f1d935/32.png) [@nicholaswogan](https://fortran-lang.discourse.group/u/nicholaswogan)\
**Post date:** [February 2, 2024, 3:54pm UTC](https://fortran-lang.discourse.group/t/description-of-a-method-in-minpack/7314/3 "2024-02-02T15:54:04Z")

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Thanks so much! I send a private message asking for the PDF. Really appreciate the info.