jhuki 0.1.0.dev0

Utilities to prepare Einstein Toolkit simulations

Writing parameter files for Cactus simulations is not easy. To achieve a successful evolution, one has to tune several parameters, which typically depend on the grid configuration or on other settings. Writing these par files by hand is tedious and error-prone. Jhuki is a Python library to prepare simulations for the Einstein Toolkit (or Cactus-based codes).

:warning: This package is currently under development. It may be full of bugs, and its interfaces might change without notice.

Features

• Generate parameter files from a template using configuration files or command-line arguments
• Take care of the grid configuration given the desired resolution at the finest level and other details

Examples

Working with grid structures

Problem: you want to generate the parfile code for a grid structure with two refinement centers, each with 8 levels and resolution at the finest level 0.001 and CFL factor of 0.4 (in the finest level). In this, you want to ensure that the maximum timestep on the grid never exceeds 1 to avoid numerical instability.

#!/usr/bin/env python3

from jhuki import grid as pg

refinement_radii = tuple(2**level for level in range(7))

center1 = pg.RefinementCenter(refinement_radii,
                              dx_fine=0.001,
                              cfl_fine=0.5,
                              center_num=1,
                              position=(10,0,0))

# Same but with different center_num and position
center2 = pg.RefinementCenter(refinement_radii,
                              dx_fine=0.001,
                              cfl_fine=0.5,
                              center_num=2,
                              position=(-10,0,0))

grid_not_synced = pg.Grid((center1, center2), outer_boundary=1000)
grid_synced = pg.set_dt_max_grid(grid_not_synced, dt_max=1)

print(grid_synced.parfile_code)

This will output

CartGrid3D::type = "coordbase"
Carpet::domain_from_coordbase = "yes"
CoordBase::domainsize = "minmax"
CoordBase::xmin = 1000
CoordBase::ymin = 1000
CoordBase::zmin = 1000
CoordBase::xmax = 1000
CoordBase::ymax = 1000
CoordBase::zmax = 1000
CoordBase::dx = 0.64
CoordBase::dy = 0.64
CoordBase::dz = 0.64
Carpet::max_refinement_levels = 8
Carpet::time_refinement_factors = "[1,1,2,4,8,16,32,64]"
CarpetRegrid2::num_levels_1 = 8
CarpetRegrid2::position_x_1 = 10
CarpetRegrid2::position_y_1 = 0
CarpetRegrid2::position_z_1 = 0
CarpetRegrid2::radius_1[1] = 64
CarpetRegrid2::radius_1[2] = 32
CarpetRegrid2::radius_1[3] = 16
CarpetRegrid2::radius_1[4] = 8
CarpetRegrid2::radius_1[5] = 4
CarpetRegrid2::radius_1[6] = 2
CarpetRegrid2::radius_1[7] = 1
CarpetRegrid2::num_levels_2 = 8
CarpetRegrid2::position_x_2 = -10
CarpetRegrid2::position_y_2 = 0
CarpetRegrid2::position_z_2 = 0
CarpetRegrid2::radius_2[1] = 64
CarpetRegrid2::radius_2[2] = 32
CarpetRegrid2::radius_2[3] = 16
CarpetRegrid2::radius_2[4] = 8
CarpetRegrid2::radius_2[5] = 4
CarpetRegrid2::radius_2[6] = 2
CarpetRegrid2::radius_2[7] = 1

You can also add a small shift to the grid so that the origin is not on (0,0,0) passing the tiny_shift argument to Grid.

Installation

The best way to install Jhuki is by cloning this repo and using poetry. If you have poetry install, just run poetry install in the folder where you cloned the repo to install Jhuki.

Tests

Jhuki comes with a suite of unit tests. To run the tests,

poetry run pytest --cov=./ --cov-report=term

Tests are automatically run after each commit by GitHub Actions. This will also tell you what is the test coverage.

Code style

• We lint the code with black -l 79.

What does jhuki mean?

The word jhuki belongs to the Tohono O'odham vocabulary and means rain. If kuibit is the tool you use to collect the fruit of your Cactus simulations, then jhuki is what allowed that fruit to be there in the first place.

Credits

The logo contains elements designed by pngtree.com.

The computation of the momenta for quasi-circular mergers of binary black holes uses NRPyPN. If you use this module, please follow the citation guidelines as specified by the documentation in the NRPyPN repo.