N-body gravitational simulation using brute-force all-pairs direct summation. Computes exact O(n^2) pairwise interactions per step — maximum accuracy baseline. Supports preset configurations (solar system, binary star, galaxy cluster, collision).
| Date | Fitness | Safety | Calls |
|---|---|---|---|
| Mar 17 | 1.0000 | 1.00 | 1 |
Brute-force N-body gravitational simulation — a pure-computation Native Gene for the Rotifer Protocol.
All-pairs direct summation with O(n²) complexity per step. For each pair of particles (i, j), computes the exact gravitational force using Newton's law with a softening parameter to prevent singularities:
F = G × m_i × m_j × r̂ / (|r|² + ε²)^(3/2)
Integration uses the symplectic leapfrog (kick-drift-kick) scheme for energy conservation.
This is the accuracy baseline — every pairwise interaction is computed exactly, making it ideal for validating approximation-based algorithms like Barnes-Hut or spatial hashing.
# Solar system preset (64 particles, 100 steps)
rotifer run particle-brute --input '{"preset": "solar"}'
# Cluster collision (128 particles, 500 steps)
rotifer run particle-brute --input '{"preset": "collision", "count": 128, "steps": 500}'
# Custom particles
rotifer run particle-brute --input '{"particles": [{"x":0,"y":0,"vx":0,"vy":0,"mass":100}, {"x":5,"y":0,"vx":0,"vy":4.47,"mass":1}]}'
| Preset | Description |
|---|---|
solar |
Central massive body + orbiting lighter bodies with circular velocities |
binary |
Two equal-mass stars in mutual orbit + debris ring |
cluster |
Random particles in a disk with small random velocities |
collision |
Two groups of particles approaching head-on |
particles — final positions and velocities of all particlessteps_computed — number of simulation steps executedtotal_energy — total system energy (kinetic + potential) for conservation validationinteractions_computed — total force evaluations (n(n-1)/2 × 2 × steps for kick-drift-kick)| Metric | Expected |
|---|---|
| Success Rate | 1.0 (deterministic, no failure mode) |
| Accuracy | Exact (machine-precision pairwise forces) |
| Complexity | O(n² × steps) |
| Interactions | n(n-1) × steps |
| Best For | Small N (≤256), accuracy benchmarks |
| Weakness | Scales poorly for large N |
{
"type": "object",
"required": [],
"properties": {
"G": {
"type": "number",
"default": 1,
"description": "Gravitational constant"
},
"dt": {
"type": "number",
"default": 0.01,
"description": "Time step size"
},
"seed": {
"type": "number",
"description": "Random seed for preset generation (deterministic output)"
},
"count": {
"type": "number",
"default": 64,
"maximum": 2048,
"minimum": 2,
"description": "Number of particles for preset generation"
},
"steps": {
"type": "number",
"default": 100,
"maximum": 10000,
"minimum": 1,
"description": "Number of simulation steps"
},
"preset": {
"enum": [
"solar",
"binary",
"cluster",
"collision"
],
"type": "string",
"description": "Preset particle configuration"
},
"particles": {
"type": "array",
"items": {
"type": "object",
"required": [
"x",
"y",
"vx",
"vy",
"mass"
],
"properties": {
"x": {
"type": "number"
},
"y": {
"type": "number"
},
"vx": {
"type": "number"
},
"vy": {
"type": "number"
},
"mass": {
"type": "number"
}
}
},
"description": "Initial particle states. Ignored if preset is provided."
},
"softening": {
"type": "number",
"default": 0.01,
"description": "Softening parameter to prevent singularity at close range"
}
}
}{
"type": "object",
"required": [
"particles",
"steps_computed",
"total_energy",
"interactions_computed"
],
"properties": {
"particles": {
"type": "array",
"items": {
"type": "object",
"properties": {
"x": {
"type": "number"
},
"y": {
"type": "number"
},
"vx": {
"type": "number"
},
"vy": {
"type": "number"
},
"mass": {
"type": "number"
}
}
},
"description": "Final particle states after simulation"
},
"total_energy": {
"type": "number",
"description": "Total system energy (kinetic + potential) at final state"
},
"steps_computed": {
"type": "number",
"description": "Actual number of simulation steps computed"
},
"interactions_computed": {
"type": "number",
"description": "Total pairwise force evaluations across all steps"
}
}
}