N-body problem: Difference between revisions
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;Task
Write a simulation of three masses interacting under gravitation and show their evolution over a number of time-steps (at least 20).
=={{header|11l}}==
{{trans|Python}}
<lang 11l>-V origin = (0.0, 0.0, 0.0)
T NBody
Float gc
Int bodies
Int timeSteps
[Float] masses
[(Float, Float, Float)] positions, velocities, accelerations
F (fileName)
V lines = File(fileName, ‘r’).read().split("\n")
V gbt = lines[0].split(‘ ’)
.gc = Float(gbt[0])
.bodies = Int(gbt[1])
.timeSteps = Int(gbt[2])
.masses = [0.0] * .bodies
.positions = [:origin] * .bodies
.velocities = [:origin] * .bodies
.accelerations = [:origin] * .bodies
L(i) 0 .< .bodies
.masses[i] = Float(lines[i * 3 + 1])
.positions[i] = .__decompose(lines[i * 3 + 2])
.velocities[i] = .__decompose(lines[i * 3 + 3])
print(‘Contents of ’fileName)
L(line) lines
print(line)
print()
print(‘Body : x y z |’, end' ‘ ’)
print(‘ vx vy vz’)
F __decompose(line)
V xyz = line.split(‘ ’)
V x = Float(xyz[0])
V y = Float(xyz[1])
V z = Float(xyz[2])
R (x, y, z)
F __computeAccelerations()
L(i) 0 .< .bodies
.accelerations[i] = :origin
L(j) 0 .< .bodies
I i != j
V temp = .gc * .masses[j] / (length(.positions[i] - .positions[j]) ^ 3)
.accelerations[i] += (.positions[j] - .positions[i]) * temp
F __computePositions()
L(i) 0 .< .bodies
.positions[i] += .velocities[i] + .accelerations[i] * 0.5
F __computeVelocities()
L(i) 0 .< .bodies
.velocities[i] += .accelerations[i]
F __resolveCollisions()
L(i) 0 .< .bodies
L(j) 0 .< .bodies
I .positions[i] == .positions[j]
swap(&.velocities[i], &.velocities[j])
F simulate()
.__computeAccelerations()
.__computePositions()
.__computeVelocities()
.__resolveCollisions()
F printResults()
L(i) 0 .< .bodies
print(‘Body #. : #2.6 #2.6 #2.6 | #2.6 #2.6 #2.6’.format(i + 1, .positions[i].x, .positions[i].y, .positions[i].z, .velocities[i].x, .velocities[i].y, .velocities[i].z))
V nb = NBody(‘nbody.txt’)
L(i) 0 .< nb.timeSteps
print("\nCycle #.".format(i + 1))
nb.simulate()
nb.printResults()</lang>
{{out}}
<pre>
Contents of nbody.txt
0.01 3 20
1
0 0 0
0.01 0 0
0.1
1 1 0
0 0 0.02
0.001
0 1 1
0.01 -0.01 -0.01
Body : x y z | vx vy vz
Cycle 1
Body 1 : 0.010177 0.000179 0.000002 | 0.010354 0.000357 0.000004
Body 2 : 0.998230 0.998232 0.020002 | -0.003539 -0.003536 0.020004
Body 3 : 0.010177 0.988232 0.988055 | 0.010354 -0.013536 -0.013889
Cycle 2
Body 1 : 0.020709 0.000718 0.000011 | 0.010710 0.000721 0.000014
Body 2 : 0.992907 0.992896 0.039971 | -0.007109 -0.007138 0.019935
Body 3 : 0.020717 0.972888 0.972173 | 0.010727 -0.017153 -0.017876
Cycle 3
Body 1 : 0.031600 0.001625 0.000034 | 0.011072 0.001094 0.000033
Body 2 : 0.983985 0.983910 0.059834 | -0.010735 -0.010835 0.019790
Body 3 : 0.031643 0.953868 0.952235 | 0.011125 -0.020886 -0.021999
...
Cycle 20
Body 1 : 0.258572 0.116046 0.112038 | -0.013129 0.000544 0.046890
Body 2 : 0.426346 -0.111425 -0.681150 | 0.234987 0.006241 -0.440245
Body 3 : -1.006089 -4.103186 -3.122591 | -0.359686 -1.177995 -0.875924
</pre>
=={{header|C}}==
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