Add objective functions (#158)

[jayspeidell]

Description

Objective Function Updates: Verified Goldstein and Booth functions working and removed TODO tags. Fixed Bulkin No 6 and removed TODO tag. Implemented Cross-in-Tray, Easom, Eggholder, Himmelblau's, Holder Table, and Three Hump Camel functions. File is getting long so I sorted the functions and added a list of functions and their corresponding function name to the docstring.

Related Issue

Add more benchmark functions #158

Motivation and Context

More is better, right?

How Has This Been Tested?

I created a notebook with all the added functions and tested each function as I implemented it. All functions function in the full domain and visually match examples found online, and the minimums are what they should be.

Then I used flask8 and black. I restricted flask8 and black testing to the file that I edited.

I also ran py.test.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[ljvmiranda921]

Ok, this is good @jayspeidell !
I'll now leave you to @whzup 👍

[jayspeidell]

I'll add the tests in tomorrow or Wednesday. I hadn't noticed that there were tests for the individual functions.

[jayspeidell]

Added tests for all the functions! Thanks for your patience, I know you've had to review this pull request a few times. I think I got it this time!

[whzup]

Looks good @jayspeidell! 🎊 Thank you a lot for your contribution! 👍 I hope you learned some things working on this PR. We always appreciate good contributors so feel free to contribute again if you want to! 💯

[Kosisochi]

Hello, how do I specify if I want to either maximize or minimize my objective function?

[whzup]

@Kosisochi If you have a question please open an issue and do not use closed issues for this purpose😅. By default, it minimizes the function if you put a negative sign to the cost function you find the maximum position.