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Gaepsi is a PYTHON extension for visualizing cosmology simulations produced by Gadget. Visualization is the most important facet of Gaepsi, but it also allows data analysis on GADGET simulations with its growing number of physics related subroutines and constants. Unlike mesh based scheme, SPH simulations are directly visible in the sense that a splatting process is required to produce raster images from the simulations. Gaepsi produces images of 2-dimensional line-of-sight projections of the simulation. Scalar fields and vector fields are both supported.
Besides the traditional way of slicing a simulation, Gaepsi also has built-in support of 'Survey-like' domain transformation proposed by Carlson & White. An improved implementation is used in Gaepsi. Gaepsi both implements an interactive shell for plotting and exposes its API for batch processing. When complied with OpenMP, Gaepsi automatically takes the advantage of the multi-core computers. In interactive mode, Gaepsi is capable of producing images of size up to 32000 x 32000 pixels. The user can zoom, pan and rotate the field with a command in on the finger tip. The interactive mode takes full advantages of matplotlib's rich annotating, labeling and image composition facilities. There are also built-in commands to add objects that are commonly used in cosmology simulations to the figures.
covdisc computes the disconnected part of the covariance matrix of 2-point functions in large-scale structure studies, accounting for the survey window effect. This method works for both power spectrum and correlation function, and applies to the covariances for various probes including the multi- poles and the wedges of 3D clustering, the angular and the projected statistics of clustering and lensing, as well as their cross covariances.
nbodykit provides algorithms for analyzing cosmological datasets from N-body simulations and large-scale structure surveys, and takes advantage of the abundance and availability of large-scale computing resources. The package provides a unified treatment of simulation and observational datasets by insulating algorithms from data containers, and reduces wall-clock time by scaling to thousands of cores. All algorithms are parallel and run with Message Passing Interface (MPI); the code is designed to be deployed on large super-computing facilities. nbodykit offers an interactive user interface that performs as well in a Jupyter notebook as on super-computing machines.
FastPM solves the gravity Possion equation with a boosted particle mesh. Arbitrary time steps can be used. The code is intended to study the formation of large scale structure and supports plain PM and Comoving-Lagranian (COLA) solvers. A broadband correction enforces the linear theory model growth factor at large scale. FastPM scales extremely well to hundred thousand MPI ranks, which is possible through the use of the PFFT Fourier Transform library. The size of mesh in FastPM can vary with time, allowing one to use coarse force mesh at high redshift with increase temporal resolution for accurate large scale modes. The code supports a variety of Greens function and differentiation kernels, though for most practical simulations the choice of kernels does not make a difference. A parameter file interpreter is provided to validate and execute the configuration files without running the simulation, allowing creative usages of the configuration files.
MADLens produces non-Gaussian cosmic shear maps at arbitrary source redshifts. A MADLens simulation with only 256^3 particles produces convergence maps whose power agree with theoretical lensing power spectra up to scales of L=10000. The code is based on a highly parallelizable particle-mesh algorithm and employs a sub-evolution scheme in the lensing projection and a machine-learning inspired sharpening step to achieve these high accuracies.