N-sample v0.1 Author: Michael D. Schneider

Code to add new large-scale Fourier mode realizations to an N-body simulation that was run without any large-scale power.

This version is not intended to readily compile on other systems, but matches the code version used for the publication below.

Please cite the following paper in any publications resulting from use of this code: M. D. Schneider, S. Cole, C. S. Frenk, and I. Szapudi, “Fast generation of ensembles of cosmological N-body simulations via mode-resampling,” arXiv, 2011. http://arxiv.org/abs/1103.2767

See the LICENSE file for terms of use and redistribution of the source code and documentation.

Dependencies (must be separately downloaded):

• FFTW (http://www.fftw.org/) v2.1.5 is required for the MPI functionality. For serial runs, FFTW v3.2.2 is also supported. If the compiler flags -DFFTW and -DMPI are both omitted then the code will compile with FFT from the Sun Performance Library. The routines in fft_nsample.f90 need to be changed for other FFT options in this case.

• FITPACK (http://www.netlib.org/fitpack/index.html) Compile without the flag -DFITPACK to remove this dependency. Log-linear interpolation of the theory power spectrum is used instead of splines in this case. Interface blocks for the necessary FITPACK routines are included io_nsample.f90 in this package.

• read_millennium Routines by John Helly, ICC Durham. These routines are not publicly available so the user of this software will need to replace the functionality for reading their own N-body snapshot files.