How to compile HPL (LINPACK)

This guide will show you how to compile HPL (Linpack) and provide some tips for selecting the best input values for hpl.dat based on my experiences at the student cluster competitions. This benchmark stresses the computers floating point operation capabilities. Although just calculating FLOPs is not reflective of applications typically run on supercomputers, floating point is still important when precise calculations are required. I assume a version of mpi, c/c++/fotran compilers, blas and whatever libraries you need are installed. There...

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How to Create Shared Folder on VirtualBox – Windows and Ubuntu

I have a Windows 10 laptop, and I am running VirtualBox. One of my virtual machines has Ubuntu 14.04 64 bit operating system. Now, I want to be able to share folders from my Ubuntu to Windows 10 and vice versa. I’m assuming that you have installed the Ubuntu virtual machine already and ready to set up the shared folder. Step 1) Make a folder to be shared on your Windows 10 host operating system. I’ll create a folder called...

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How to use MPI without NFS

You can use MPI without NFS or a shared file system! We had a situation where we couldn’t find the NFS server or client packages for arm64 for Ubuntu 16.04. We had OpenMPI version 1.10.2 installed on 2 nodes without NFS. When you use MPI without NFS, you need to ensure that the same version of MPI is installed by every node. Then, you have to ensure that the same data files, which include the program, hostnames file, and input files,...

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How to Fix OpenMPI ORTE Error: unknown option “–hnp-topo-sig”

We encountered an ORTE bug with the error message, Error: unknown option “–hnp-topo-sig”, while using OpenMPI version 1.10.2 for arm64 on Ubuntu 14.04 server. More specifically, we ran the following command using 2 nodes with MPI: mpirun –hostfile /nfs/hostnames -n 4 /nfs/mpi-hello-world/mpi_hello_world

ORTE errors can happen because of a variety of different things, but it’s usually because your mpirun is not the same version as your mpi compiler. Even if you think that you only have one MPI version, you may in...

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How to Get Multiple Terminals on Ubuntu Server

Let’s say that you want multiple terminals on an Ubuntu server. If you have ever used the Ubuntu server version of the OS, you should know that it is maneuvered only through the terminal. We had a situation where we didn’t have access to the Internet, so we couldn’t install something like tmux for multi-tasking, and we thought screen was hard to use. We needed multiple terminals, so that we could run multiple commands at the same time! If you...

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How to Download Packages and Dependencies from Different Architectures on Ubuntu

Let’s say that I have a computer that I installed Ubuntu 14.04 x86-64 also known as amd64. I want to download a package, but I want to download the package and its dependencies from a different architecture instead of amd64. In this scenario, I want to download a package from arm64 architecture. Enable Another Architecture to Download First, we will add a new architecture to be able to select when installing or downloading any package. Instead of arm64, you can substitute...

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How to Download Packages and Dependencies Locally on Ubuntu

I want to download a package and all of its dependencies that I would typically use apt-get to install on Ubuntu. How do I download a package and its dependencies locally on Ubuntu? I am using Ubuntu 14.04 and Ubuntu 16.04 for this tutorial. How to Download Ubuntu Packages and Dependencies Locally We require Internet access to download the packages locally. First, we should always update our package sources. sudo apt-get update Afterwards, we should make a directory to store...

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How to SSH to Another Computer with Ethernet Cable – Local Area Network

Let’s say that we wanted to connect an Ethernet cable from Ethernet port of one computer to Ethernet port of another computer. I want to be able to SSH into the other machine from my computer given that I know the other machine’s password or have an authenticated SSH key. You can also SSH to a series of machines if you have a switch with all the other machines connected to that switch through Ethernet cables. The switch is basically a...

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How to Set Static IP on Ubuntu

To set the static IP address on Ubuntu, we want to first determine what network interfaces we currently have. These network interfaces represent the Infiniband or Ethernet ports on your computer. You will typically have an interface called eth0 or eth1 that allows you to connect to the Internet. Note, setting the static IP will allow you to connect to the Internet as long as the IP address is valid according to your DHCP server. If you set any static IP...

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Fixing 500 Internal Server Error for a PHP File

The 500 Internal Server Error, which you may be seeing on the web console, may occur because of a random PHP file. 500 Internal Server Error may happen because of faulty .htaccess configuration, PHP memory limit, or a slew of other random issues. I’ll show you how I normally debug and fix the 500 Internal Server Error for PHP files for most scenarios. Press F12 on Google Chrome and look at the Console tab to see if a PHP file...

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