Nbody Save
N body gravity attraction problem solver
Project README
N-body simulation program
Features
Integration methods
| Method alias | Order | Description | Implicit | Dynamic step |
|---|---|---|---|---|
| adams | up to 5 | Adams–Bashforth method | :heavy_minus_sign: | :heavy_minus_sign: |
| bs | 2*max_level |
Bulirsch-Stoer method | :heavy_minus_sign: | :star: |
| euler | 1 | Classic Euler method | :heavy_minus_sign: | :heavy_minus_sign: |
| midpoint | 2 | Midpoint method | :heavy_minus_sign: | :heavy_minus_sign: |
| midpoint-st | 2 | Midpoint method (Stetter modification. See 1) p. 228) | :star: | :heavy_minus_sign: |
| rk4 | 4 | Classic Runge-Kutta 4-order method | :heavy_minus_sign: | :heavy_minus_sign: |
| rk_butcher | - | Runge-Kutta method with arbitrary Butcher tableu | :heavy_minus_sign: | :heavy_minus_sign: |
| rkck | 5 | Runge-Kutta-Cash–Karp 5-order method | :heavy_minus_sign: | :star: |
| rkdp | 5 | Runge-Kutta-Dormand–Prince 5-order method | :heavy_minus_sign: | :star: |
| rkdverk | 5 | Runge-Kutta-Verner 5-order method. See 1) p. 181 | :heavy_minus_sign: | :star: |
| rkf | 7 | Runge-Kutta-Fehlberg 7-order method. See 1) p. 180 | :heavy_minus_sign: | :star: |
| rkfeagin10 | 10 | Runge-Kutta-Feagin 10-order method. See 4) | :heavy_minus_sign: | :star: |
| rkfeagin12 | 12 | Runge-Kutta-Feagin 12-order method. | :heavy_minus_sign: | :star: |
| rkfeagin14 | 14 | Runge-Kutta-Feagin 14-order method. | :heavy_minus_sign: | :star: |
| rkgl | 6 | Gauss–Legendre 6-order method | :star: | :heavy_minus_sign: |
| rklc | 4 | Runge-Kutta-Lobatto IIIC 4-order method | :star: | :star: |
| trapeze | 2 | Trapeze method | :star: | :heavy_minus_sign: |
Compute engines
| Engine alias | Approximate | Description |
|---|---|---|
| ah | :star: | Single threaded engine with Ahmad-Cohen universe force simulation. See 2) |
| block | :heavy_minus_sign: | Multi-threaded (OpenMP) engine with block-by-block force computation |
| cuda | :heavy_minus_sign: | Parallel CUDA engine |
| cuda_bh | :star: | CUDA engine with Burnes-Hut force simulation |
| cuda_bh_tex | :star: | CUDA engine with Burnes-Hut force simulation and with bodies tree stored at texture memory. Possible tree layout is 'heap' and 'heap_stackless' |
| opencl | :heavy_minus_sign: | Parallel OpenCL engine |
| opencl_bh | :star: | Parallel OpenCL engine with Burnes-Hut force simulation |
| openmp | :heavy_minus_sign: | Multi-threaded (OpenMP) engine |
| simple | :heavy_minus_sign: | Simple single threaded engine |
| simple_bh | :star: | Multi-threaded (OpenMP) engine with Burnes-Hut force simulation |
How to run
Simulation
To run n-body problem simulation use 'nbody-simulation' program.
Simulation control
| Argument | Description |
|---|---|
--stars_count |
Stars count |
--box_size |
'Universe' box size. |
--output |
Output stream name. |
--resume |
Stream name to resume (in this case output and initial_state are ignored). |
--initial_state |
Optional initial state file |
--initial_type |
Initial state type. Possible values are: Zeno, G1, SI, ADK. See initial state types table. |
--max_part_size |
Max stream file size (splits a stream into multiple files). |
--max_time |
Max simulation time. |
--dump_step |
Time step to dump simulation state to stream. |
--check_step |
Time step to verify the fundamental laws of physics. Conservation of impulse [P], angular momentum [L], energy [E], mass center velocity [V]. |
--check_list |
List of fundamental laws of physics to check. For example --check_list=PL to check only conservation of impulse [P] and angular momentum [L]. |
--verbose |
Print detailed simulation information. |
Initial state types
| Type | Description |
|---|---|
Zeno |
File in 'Zeno' format. Can be created with snapascii tool. |
G1 |
Plane text table with Rx Ry Rz Vx Vy Vz M values. Space as separator. |
SI |
Plane text table same format as G1. Units are meter, second, kilogram. On load mass will be multiplied by MassFactorSI to convert to G1 type. |
ADK |
Plane text table same format as G1. Units are astronomical unit, day, kilogram. On load mass will be multiplied by MassFactorAuDayKg to convert to G1 type. |
Engine control arguments are:
| Argument | Description |
|---|---|
--engine |
Compute engine type. |
--distance_to_node_radius_ratio |
Simulation accuracy control for Burnes-Hut engines. |
--traverse_type |
Space tree traverse type for Burnes-Hut engine. Possible values are cycle or nested_tree. |
--tree_layout |
Space tree layout type for Burnes-Hut engine. Possible values are tree or heap. |
--tree_build_rate |
Full tree build rate in cucles for Burnes-Hut engine. Only boxes geometry are rebuild between full builds, cells layout is not changed. If 0 than full tree build occurs on each compute. |
--full_recompute_rate |
Full force recompute rate in cucles (Ahmad-Cohen engine). |
--max_dist |
The maximum distance at which the force is calculated completely at each step (Ahmad-Cohen engine). |
--min_force |
The minimum force of attraction at which it is calculated completely at each step (Ahmad-Cohen engine). |
--device |
Platforms/devices list for OpenCL based engines. Format: Platform1_ID:Device1,Device2;Platform2_ID:Device1,Device2... For example: --device=0:0,1 - first and second devices from first platform (with same context), --device=0:0;0:1 - first and second devices from first platform (with separate contexts) |
--oclprof |
Enable OpenCL profile |
--block_size |
Data block size to load at local OpenCL/CUDA memory |
--use_nccl |
Use libNCCL for CUDA multi GPU communications (default: false) |
Solver control arguments are:
| Argument | Description |
|---|---|
--solver |
Solver type. |
--max_step |
Solvers max time step |
--min_step |
Embedded solvers min time step |
--rank |
Adams–Bashforth solver rank (1...5). |
--correction |
Kahan summation at each integration step (for now at Adams–Bashforth and Runge-Kutta solvers) |
--starter_solver |
Adams–Bashforth starter solver. |
--refine_steps_count |
Refine step count for implicit solvers. |
--error_threshold |
Step error threshold for solvers with dynamic step. If the error at the current step is greater than the threshold, then we decrease the time step and repeat the step. |
--max_recursion |
Max recursion level for embeded solvers. |
--substep_subdivisions |
Number of embeded solver substeps into which the current step is divided at the next level of recursion when the error greater than error_threshold. |
--max_level |
Maximum extrapolation table size for Bulirsch-Stoer solver |
--clamp |
Clamp outliers coordinates to bounding box |
Player
To view simulation results run 'nbody-player' program.
| Argument | Description |
|---|---|
--input |
Input stream name. |
--check_list |
List of fundamental laws of physics to check. For example --check_list=PL to check only conservation of impulse [P] and angular momentum [L]. |
Other parameters controlled via UI.
Gallery
Refs
- Hairer, Ernst; Nørsett, Syvert Paul; Wanner, Gerhard (1993), Solving ordinary differential equations I: Nonstiff problems, Berlin, New York
- A Numerical Integration Scheme for the N-Body Gravitational Problem A. AHMAD AND L. COHEN 1973
- Задача N тел или как взорвать галактику не выходя из кухни
- Feagin T. A tenth-order Runge–Kutta method with error estimate. In: Proc. of the IAENG Conf. on Scientific Computing. Hong Kong, 2007.
Open Source Agenda is not affiliated with "Nbody" Project. README Source: drons/nbody
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Open Issues
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Last Commit
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