# Latest **URL:** https://forum.ysang.org/latest.md [Latest](https://forum.ysang.org/latest.md) · [Categories](https://forum.ysang.org/categories.md) --- ## [Welcome to the Forum of Our Lab!](https://forum.ysang.org/t/welcome-to-the-forum-of-our-lab/7)
**Author:** [@system](https://forum.ysang.org/u/system)\ **Replies:** 0\ **Last updated:** [June 6, 2020, 11:57pm UTC](https://forum.ysang.org/t/welcome-to-the-forum-of-our-lab/7 "2020-06-06T23:57:08Z")
Hello! Welcome to the online community for our lab :tada: I always believe a good community is a great catalyst for success. As researchers, we explore unknown territories and it’s quite normal to hit rough patches ever… --- ## [SLURM-based Raspberry Pi 400 Computing Cluster Setup Tutorial](https://forum.ysang.org/t/slurm-based-raspberry-pi-400-computing-cluster-setup-tutorial/58)
**Author:** [@jelopezmolinab](https://forum.ysang.org/u/jelopezmolinab)\ **Replies:** 0\ **Last updated:** [August 4, 2023, 7:45am UTC](https://forum.ysang.org/t/slurm-based-raspberry-pi-400-computing-cluster-setup-tutorial/58 "2023-08-04T07:45:38Z")
Hello! In this forum I will be posting a tutorial on how to build a Raspberry Pi 400 computer cluster using SLURM daemon controllers, as well as a troubleshooting guide for help on verifying where you might’ve committed … --- ## [Setting Up SSH (Secure Shell) Before OS (Operating System) Install](https://forum.ysang.org/t/setting-up-ssh-secure-shell-before-os-operating-system-install/55)
**Author:** [@Jciriza](https://forum.ysang.org/u/Jciriza)\ **Replies:** 0\ **Last updated:** [May 10, 2023, 7:17pm UTC](https://forum.ysang.org/t/setting-up-ssh-secure-shell-before-os-operating-system-install/55 "2023-05-10T19:17:09Z")
Hello all! The following tutorial is meant for users that are setting up SSH during their OS install. Enabling SSH will open up opportunities to increase the effectiveness of parallel computing. --- ## [Setting Up SSH (Secure Shell) after OS (Operating System) Install](https://forum.ysang.org/t/setting-up-ssh-secure-shell-after-os-operating-system-install/54)
**Author:** [@Jciriza](https://forum.ysang.org/u/Jciriza)\ **Replies:** 0\ **Last updated:** [May 10, 2023, 6:26pm UTC](https://forum.ysang.org/t/setting-up-ssh-secure-shell-after-os-operating-system-install/54 "2023-05-10T18:26:36Z")
Hello all! While Parallel computing can be done on one device, using cores as nodes, it can bottle the potential of your computing capabilities. Below are instructions to set up the SSH client so that we can eventually… --- ## [Reformatting Disk (Microsoft)](https://forum.ysang.org/t/reformatting-disk-microsoft/53)
**Author:** [@Jciriza](https://forum.ysang.org/u/Jciriza)\ **Replies:** 0\ **Last updated:** [May 10, 2023, 6:14pm UTC](https://forum.ysang.org/t/reformatting-disk-microsoft/53 "2023-05-10T18:14:56Z")
Hello all! Below you will find instructions on how to reformat a SD card if it ever gives you issues. Keep in mind that when you reformat a disk all the data is deleted so be sure to save any work previously installed … --- ## [Cloning a GitHub Repository](https://forum.ysang.org/t/cloning-a-github-repository/48)
**Author:** [@ksantacruz](https://forum.ysang.org/u/ksantacruz)\ **Replies:** 0\ **Last updated:** [February 26, 2023, 5:06am UTC](https://forum.ysang.org/t/cloning-a-github-repository/48 "2023-02-26T05:06:29Z")
Notes Cloning a GitHub repository pulls a copy of the files found on the website along with all versions of the projects. This allows users to push their own changes to the remote repository or pull changes that others … --- ## [Setting up a Local Repository in GitHub using Git](https://forum.ysang.org/t/setting-up-a-local-repository-in-github-using-git/47)
**Author:** [@ksantacruz](https://forum.ysang.org/u/ksantacruz)\ **Replies:** 1\ **Last updated:** [February 26, 2023, 12:17am UTC](https://forum.ysang.org/t/setting-up-a-local-repository-in-github-using-git/47 "2023-02-26T00:17:04Z")
Notes GitHub is a version control system that can be used to keep track of versions of codes for projects we work on in our lab. In addition, it can be used to collaborate with others on the same projects. 1. Create a … --- ## [Setting up Julia JuMP](https://forum.ysang.org/t/setting-up-julia-jump/38)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [April 9, 2021, 8:46pm UTC](https://forum.ysang.org/t/setting-up-julia-jump/38 "2021-04-09T20:46:30Z")
Notes You could find an installation guide on the official website: Installation Guide · JuMP Here in my tutorial I will provide some notes on the pitfalls that I experienced. Basic JuMP Installation Download and insta… --- ## [How to connect to WPA2-Enterprise wifi](https://forum.ysang.org/t/how-to-connect-to-wpa2-enterprise-wifi/46)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [September 2, 2022, 1:31am UTC](https://forum.ysang.org/t/how-to-connect-to-wpa2-enterprise-wifi/46 "2022-09-02T01:31:47Z")
Connecting to the university wifi is such a pain on Raspberry Pi 400 because the default settings were not right and it was impossible to select the right one in the UI. Please follow the following steps: In the UI, co… --- ## [Set up Julia and Gurobi on a Raspberry Pi 400](https://forum.ysang.org/t/set-up-julia-and-gurobi-on-a-raspberry-pi-400/45)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [August 30, 2022, 10:18pm UTC](https://forum.ysang.org/t/set-up-julia-and-gurobi-on-a-raspberry-pi-400/45 "2022-08-30T22:18:10Z")
Install a 64-bit Ubuntu OS (Gurobi requires a 64-bit OS): Download Raspberry Pi Imager at https://www.raspberrypi.com/software/ and install it on a regular computer. Download the Ubuntu Image for Raspberry Pi at Install… --- ## [Python, Anaconda, Gurobi, and Pyomo Installation](https://forum.ysang.org/t/python-anaconda-gurobi-and-pyomo-installation/42)
**Author:** [@ldramirez](https://forum.ysang.org/u/ldramirez)\ **Replies:** 0\ **Last updated:** [June 25, 2021, 11:41pm UTC](https://forum.ysang.org/t/python-anaconda-gurobi-and-pyomo-installation/42 "2021-06-25T23:41:08Z")
1. Installing Python with Anaconda (Recomended) Anaconda installation is not necessary but it is the easiest way to manage environments and packages with a user friendly interface, it also comes with preinstalled usef… --- ## [What to do if our optimization problem is infeasible](https://forum.ysang.org/t/what-to-do-if-our-optimization-problem-is-infeasible/19)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [June 9, 2020, 11:19pm UTC](https://forum.ysang.org/t/what-to-do-if-our-optimization-problem-is-infeasible/19 "2020-06-09T23:19:10Z")
When we run our C++ Gurobi code, sometimes we end up getting a result saying the problem is “infeasible”. How do we figure out makes the code infeasible? First thing first, if you are using a reusable code, your code wa… --- ## [Setting up Gurobi with C++ in the Linux environment](https://forum.ysang.org/t/setting-up-gurobi-with-c-in-the-linux-environment/13)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 2\ **Last updated:** [February 3, 2021, 8:00pm UTC](https://forum.ysang.org/t/setting-up-gurobi-with-c-in-the-linux-environment/13 "2021-02-03T20:00:48Z")
Install Windows Subsystem for Linux and install necessary packages. WSL1 is good enough. No need to update to WSL2. Tutorial: https://docs.microsoft.com/en-us/windows/wsl/install-win10 Open the Microsoft Store app, a… --- ## [How to set the MIP gap](https://forum.ysang.org/t/how-to-set-the-mip-gap/30)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 1\ **Last updated:** [August 18, 2020, 4:05am UTC](https://forum.ysang.org/t/how-to-set-the-mip-gap/30 "2020-08-18T04:05:05Z")
There is a MIP gap for every mixed-integer problem. The default MIP gap for Gurobi is 1e-4. However, you could do some settings to change this value. It can be any non-negative value. Warning: Most of the time, a MIP ga… --- ## [How to read test system data](https://forum.ysang.org/t/how-to-read-test-system-data/33)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [August 4, 2020, 5:03pm UTC](https://forum.ysang.org/t/how-to-read-test-system-data/33 "2020-08-04T17:03:41Z")
If the test system just has 3 buses, we could define the system in the C++ code. However, if the system is not that small, it would take a lot of work to define the system in the C++ code. What I do is: Use .txt files… --- ## [How to output the results from Gurobi](https://forum.ysang.org/t/how-to-output-the-results-from-gurobi/31)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [August 4, 2020, 3:42pm UTC](https://forum.ysang.org/t/how-to-output-the-results-from-gurobi/31 "2020-08-04T15:42:26Z")
Once you run the code MyModel.optimize(); you will be able to solve the problem, and the objective value will be displayed in the command window automatically. However, the values of the variables will not be displayed a… --- ## [How to track the solution time of the optimization problem](https://forum.ysang.org/t/how-to-track-the-solution-time-of-the-optimization-problem/32)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [August 4, 2020, 4:01pm UTC](https://forum.ysang.org/t/how-to-track-the-solution-time-of-the-optimization-problem/32 "2020-08-04T16:01:25Z")
After the optimization problem is solved, the solution time will be displayed in the command window, shown as follows: You could record the solution time manually, however, there is a method that you could save the so… --- ## [How to get the dual value of a constraint using C++&Gurobi?](https://forum.ysang.org/t/how-to-get-the-dual-value-of-a-constraint-using-c-gurobi/28)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [August 4, 2020, 12:16am UTC](https://forum.ysang.org/t/how-to-get-the-dual-value-of-a-constraint-using-c-gurobi/28 "2020-08-04T00:16:11Z")
First thing first, if you are solving mixed-integer programs (MIP), including mixed-integer linear programs (MILP), you are out of luck, because Gurobi does not support getting dual values for mixed-integer problems. You… --- ## [Finding the runtime error in your C++ code](https://forum.ysang.org/t/finding-the-runtime-error-in-your-c-code/15)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [June 7, 2020, 11:39pm UTC](https://forum.ysang.org/t/finding-the-runtime-error-in-your-c-code/15 "2020-06-07T23:39:31Z")
There are two types of errors in the C++ code that you may encounter: (1) Errors that show up when you compile the code (2) Errors that show up when you run the code (runtime error) For error Type (1), it is relativel… --- ## [How to catch the runtime error](https://forum.ysang.org/t/how-to-catch-the-runtime-error/29)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [August 4, 2020, 3:24am UTC](https://forum.ysang.org/t/how-to-catch-the-runtime-error/29 "2020-08-04T03:24:55Z")
We talked about how to find the runtime error in a previous post (Finding the runtime error in your C++ code). Many times, we could figure out what the error is by checking the code closely once figure out which part of … --- ## [Is 0.8% of error worth your attention?](https://forum.ysang.org/t/is-0-8-of-error-worth-your-attention/27)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [July 20, 2020, 12:18am UTC](https://forum.ysang.org/t/is-0-8-of-error-worth-your-attention/27 "2020-07-20T00:18:08Z")
Recently, I got the code for a mixed-integer linear programming (MILP) problem implemented using C++&Gurobi. The objective value of this optimization problem is 1.97308e6, while the correct answer that I got from a previ… --- ## [Set up SSH remote access for Windows Subsystem for Linux (WSL)](https://forum.ysang.org/t/set-up-ssh-remote-access-for-windows-subsystem-for-linux-wsl/26)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [July 4, 2020, 11:41pm UTC](https://forum.ysang.org/t/set-up-ssh-remote-access-for-windows-subsystem-for-linux-wsl/26 "2020-07-04T23:41:29Z")
To access lab computers remotely, you could use TeamViewer in the Windows environment. However, it gets stuck sometimes and the experience is just not perfect. Since we usually run our code in the Linux environment, it w… --- ## [Defining the objective function in Gurobi](https://forum.ysang.org/t/defining-the-objective-function-in-gurobi/25)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [June 11, 2020, 5:37pm UTC](https://forum.ysang.org/t/defining-the-objective-function-in-gurobi/25 "2020-06-11T17:37:14Z")
There two methods using which you could define objective functions. ===================================================== The first one is to define the objective explicitly: GRBVar x = SimpleExample.addVar(0, 50, 20… --- ## [C++ Gurobi programming for Beginners](https://forum.ysang.org/t/c-gurobi-programming-for-beginners/20)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [June 10, 2020, 12:24am UTC](https://forum.ysang.org/t/c-gurobi-programming-for-beginners/20 "2020-06-10T00:24:38Z")
Hey! Once you set up your C++ and Gurobi, you might want to quickly start solving your first problem! (If you haven’t set up your C++ and Gurobi under the Linux environment and don’t know how to compile and run a code un… --- ## [Make your posts easier to read using the Markdown language](https://forum.ysang.org/t/make-your-posts-easier-to-read-using-the-markdown-language/23)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [June 10, 2020, 12:58am UTC](https://forum.ysang.org/t/make-your-posts-easier-to-read-using-the-markdown-language/23 "2020-06-10T00:58:20Z")
A tutorial on the markdown language is here: https://commonmark.org/help/ What I find particularly useful is the for the code blocks - if you type \`\`\` at the beginning and the end of your code, then your code is formatt… --- ## [How to access the forum using the mobile app](https://forum.ysang.org/t/how-to-access-the-forum-using-the-mobile-app/17)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [June 8, 2020, 12:03am UTC](https://forum.ysang.org/t/how-to-access-the-forum-using-the-mobile-app/17 "2020-06-08T00:03:04Z")
You can now access our online forum by downloading the mobile app Discourse. Follow the directions below to access our forum on your mobile device: 1.) Download the Discourse app to your device. Depending on which app s… --- ## [Removing null characters](https://forum.ysang.org/t/removing-null-characters/14)
**Author:** [@yuanruisang](https://forum.ysang.org/u/yuanruisang)\ **Replies:** 0\ **Last updated:** [June 7, 2020, 6:17am UTC](https://forum.ysang.org/t/removing-null-characters/14 "2020-06-07T06:17:42Z")
Once when I was compiling my code under the Linux environment, and bash told me that there were a lot of errors in my code - because my code had a lot of null characters. I used the following command to remove the null c…