MUSIC/README.md

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MUSIC v2 - multi-scale cosmological initial conditions
======================================================

MUSIC is a computer program to generate nested grid initial conditions for high-resolution "zoom" cosmological simulations. A detailed description of some of the algorithms can be found in [Hahn & Abel (2011)](http://arxiv.org/abs/1103.6031), but version 2.0 is much improved and has a much lower memory footprint. To learn how to use MUSIC, please [read the Wiki](https://github.com/cosmo-sims/music/wiki). 

Current MUSIC key features include:

- Supports output for RAMSES, ENZO, Arepo, Swift, Gadget-2/3, ART, Pkdgrav/Gasoline and NyX via plugins. New codes can be added.
- Support for first (1LPT) and second order (2LPT) Lagrangian perturbation theory.
- Full integration of the [PANPHASIA](https://arxiv.org/abs/1306.5968) hierarchical Gaussian random fields
- Pluggable transfer functions, currently CAMB, Eisenstein&Hu, BBKS, Warm Dark Matter variants. Distinct baryon+CDM fields.
- Minimum bounding ellipsoid and convex hull shaped high-res regions supported with most codes, supports refinement mask generation for RAMSES.
- Parallelized with OpenMP
- Requires FFTW3, GSL (and HDF5 for output for some codes)

## Building MUSIC
While we still supply the old Makefile, using CMake is now the preferred way of building. CMake use out-of-source build, i.e. you create a build directory, and then configure the code using CMake. Inside the `music` directory, do
```
  mkdir build
  cd build
  ccmake ..
  make -j
```
to configure the code (you will se a menu), and then start a parallel compilation. If CMake has trouble finding your FFTW or HDF5 installation, you can add hints as follows
```
  FFTW3_ROOT=<path> HDF5_ROOT=<path> ccmake ..
```
If you want to build on macOS, then it is strongly recommended to use GNU (or Intel) compilers instead of Apple's Clang. Install them e.g. via homebrew and then configure cmake to use them instead of the macOS default compiler via
```
  CC=gcc-13 CXX=g++-13 ccmake ..
```
This is necessary since Apple's compilers haven't supported OpenMP for years.


## Running
There is an example parameter file 'example.conf' in the main directory. Possible options are explained in it, it can be run as a simple argument, e.g. from within the build directory:
```
  ./MUSIC ../ics_example.conf
```


## Disclaimer
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. By downloading and using MUSIC, you agree to the LICENSE, distributed with the source code in a text file of the same name.