Doc

If you wish to run QuESTlink in multithreaded or GPU-accelerated modes, or as a server, you will need to download and manually compile it. Below are instructions for getting QuESTlink up and running, when it doesn't quite run out-of-the-box.

• Tools
• Download
• Compile
• Launch offline
• Launch as a server

---

Tools

Don't have a compiler handy? We recommend the comprehensive guide for the parent QuEST project to obtain the tools needed below.

Download

The best way to download the QuESTlink source code is through git at the command-line.

git clone --recurse-submodules https://github.com/QTechTheory/QuESTlink.git
cd QuESTlink

This will also download the QuEST submodule source-code. You are thereafter in the root directory of QuESTlink and ready to compile.

If you wish to compile a specific Github branch like develop, simply additionally run

git checkout develop

You can also perform this within the /QuEST subdirectory to change the branch of the QuEST submodule and access in-development features.

---

Compile

Compiling is trivial with GNUMake and the provided makefile, and a C++ compiler (which supports C++11).

See here for a comprehensive guide to compiling QuESTlink on Windows, including how to obtain the necessary compilers.

Note Linux users should first run sudo apt-get install uuid-dev before compiling. If this fails (and/or compiling says cannot find -luuid), also try to install uuid, uuid-devel and libuuid-devel. On a SLURM cluster, this can often be resolved with module load util-linux.

Within the root directory, edit the makefile and set:

• OS to your operating system (LINUX, MACOS or WINDOWS)

• COMPILER to your C++11 compiler command.

  If in doubt, leave this as g++

• COMPILER_TYPE to the type of your compiler (GNU, INTEL, CLANG or MSVC).

  If in doubt, run g++ --version in terminal for a clue. Otherwise, COMPILER_TYPE will likely match your OS, as: LINUX & GNU, MACOS & CLANG, WINDOWS & MSVC.

• MULTITHREADED = 1 to compile in multithreaded mode

  After compiling, and before calling CreateLocalQuESTEnv[], you should set (in terminal)

  export OMP_NUM_THREADS=<nthreads>
  

  replacing <nthreads> with the number of CPU cores of your machine, minus a few (sparing them for the Mathematica kernel itself).

  Note MULTITHREADED mode requires an OpenMP-compatible compiler. MacOS users should thus avoid clang, and download/use a GNU compiler (e.g. gcc@8).

• GPUACCELERATED = 1 to use an NVIDIA GPU.

  This requires an nvcc compiler compatible with your chosen COMPILER. The nvcc compiler command can be changed by overwriting CUDA_COMPILER in the makefile. An nvcc compiler can be obtained on Linux with sudo apt install nvidia-cuda-toolkit

  Note you must also set GPU_COMPUTE_CAPABILITY in the makefile to the CC corresponding to your GPU. You can look this up here.

With these settings set, QuESTlink is compiled from terminal, in the root directory QuESTlink/, via

make

Compiling will create an executable quest_link, and some other build files. These other unneeded files can be removed with

make tidy 

leaving only quest_link.

Should you wish to remove all compiled files and start again, run

make clean 

From within Mathematica, the compiled quest_link environment is connected to via

Import[...]
CreateLocalQuESTEnv["path/to/quest_link"];

---

Launch offline

QuESTlink can be launched without an internet connection, using a copy of this repository. In Mathematica, simply run

Import["path/to/QuESTlink/Link/QuESlink.m"];
CreateLocalQuESTEnv["path/to/quest_link"];

where quest_link has been compiled as above, or previously obtained using

CreateDownloadedQuESTEnv[];

Launch as a server

To launch quest_link as a server, to access remotely from a local kernel, run

./quest_link -linkcreate -linkprotocol TCPIP -linkname <PORT1>@<IP>,<PORT2>@<IP>

substituting <PORT1> and <PORT2> with two open and available ports, and <IP> with the server IP or domain name.

Then in your local Mathematica kernel, connect to it via

CreateRemoteQuESTEnv[<IP>, <PORT1>, <PORT2>];