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"""
N-body benchmark from the Computer Language Benchmarks Game.
This is intended to support Unladen Swallow's pyperf.py. Accordingly, it has been
modified from the Shootout version:
- Accept standard Unladen Swallow benchmark options.
- Run report_energy()/advance() in a loop.
- Reimplement itertools.combinations() to work with older Python versions.
Pulled from:
http://benchmarksgame.alioth.debian.org/u64q/program.php?test=nbody&lang=python3&id=1
Contributed by Kevin Carson.
Modified by Tupteq, Fredrik Johansson, and Daniel Nanz.
"""
import pyperf
from memray_helper import get_tracker
__contact__ = "collinwinter@google.com (Collin Winter)"
DEFAULT_ITERATIONS = 20000
DEFAULT_REFERENCE = "sun"
def combinations(l):
"""Pure-Python implementation of itertools.combinations(l, 2)."""
result = []
for x in range(len(l) - 1):
ls = l[x + 1 :]
for y in ls:
result.append((l[x], y))
return result
PI = 3.14159265358979323
SOLAR_MASS = 4 * PI * PI
DAYS_PER_YEAR = 365.24
BODIES = {
"sun": ([0.0, 0.0, 0.0], [0.0, 0.0, 0.0], SOLAR_MASS),
"jupiter": (
[4.84143144246472090e00, -1.16032004402742839e00, -1.03622044471123109e-01],
[
1.66007664274403694e-03 * DAYS_PER_YEAR,
7.69901118419740425e-03 * DAYS_PER_YEAR,
-6.90460016972063023e-05 * DAYS_PER_YEAR,
],
9.54791938424326609e-04 * SOLAR_MASS,
),
"saturn": (
[8.34336671824457987e00, 4.12479856412430479e00, -4.03523417114321381e-01],
[
-2.76742510726862411e-03 * DAYS_PER_YEAR,
4.99852801234917238e-03 * DAYS_PER_YEAR,
2.30417297573763929e-05 * DAYS_PER_YEAR,
],
2.85885980666130812e-04 * SOLAR_MASS,
),
"uranus": (
[1.28943695621391310e01, -1.51111514016986312e01, -2.23307578892655734e-01],
[
2.96460137564761618e-03 * DAYS_PER_YEAR,
2.37847173959480950e-03 * DAYS_PER_YEAR,
-2.96589568540237556e-05 * DAYS_PER_YEAR,
],
4.36624404335156298e-05 * SOLAR_MASS,
),
"neptune": (
[1.53796971148509165e01, -2.59193146099879641e01, 1.79258772950371181e-01],
[
2.68067772490389322e-03 * DAYS_PER_YEAR,
1.62824170038242295e-03 * DAYS_PER_YEAR,
-9.51592254519715870e-05 * DAYS_PER_YEAR,
],
5.15138902046611451e-05 * SOLAR_MASS,
),
}
SYSTEM = list(BODIES.values())
PAIRS = combinations(SYSTEM)
def advance(dt, n, bodies=SYSTEM, pairs=PAIRS):
for i in range(n):
for (([x1, y1, z1], v1, m1), ([x2, y2, z2], v2, m2)) in pairs:
dx = x1 - x2
dy = y1 - y2
dz = z1 - z2
mag = dt * ((dx * dx + dy * dy + dz * dz) ** (-1.5))
b1m = m1 * mag
b2m = m2 * mag
v1[0] -= dx * b2m
v1[1] -= dy * b2m
v1[2] -= dz * b2m
v2[0] += dx * b1m
v2[1] += dy * b1m
v2[2] += dz * b1m
for (r, [vx, vy, vz], m) in bodies:
r[0] += dt * vx
r[1] += dt * vy
r[2] += dt * vz
def report_energy(bodies=SYSTEM, pairs=PAIRS, e=0.0):
for (((x1, y1, z1), v1, m1), ((x2, y2, z2), v2, m2)) in pairs:
dx = x1 - x2
dy = y1 - y2
dz = z1 - z2
e -= (m1 * m2) / ((dx * dx + dy * dy + dz * dz) ** 0.5)
for (r, [vx, vy, vz], m) in bodies:
e += m * (vx * vx + vy * vy + vz * vz) / 2.0
return e
def offset_momentum(ref, bodies=SYSTEM, px=0.0, py=0.0, pz=0.0):
for (r, [vx, vy, vz], m) in bodies:
px -= vx * m
py -= vy * m
pz -= vz * m
(r, v, m) = ref
v[0] = px / m
v[1] = py / m
v[2] = pz / m
def bench_nbody(loops, reference, iterations):
# Set up global state
offset_momentum(BODIES[reference])
range_it = range(loops)
with get_tracker():
t0 = pyperf.perf_counter()
for _ in range_it:
report_energy()
advance(0.01, iterations)
report_energy()
return pyperf.perf_counter() - t0
def add_cmdline_args(cmd, args):
cmd.extend(("--iterations", str(args.iterations)))
if __name__ == "__main__":
runner = pyperf.Runner(add_cmdline_args=add_cmdline_args)
runner.metadata["description"] = "n-body benchmark"
runner.argparser.add_argument(
"--iterations",
type=int,
default=DEFAULT_ITERATIONS,
help="Number of nbody advance() iterations "
"(default: %s)" % DEFAULT_ITERATIONS,
)
runner.argparser.add_argument(
"--reference",
type=str,
default=DEFAULT_REFERENCE,
help="nbody reference (default: %s)" % DEFAULT_REFERENCE,
)
args = runner.parse_args()
runner.bench_time_func("nbody", bench_nbody, args.reference, args.iterations)
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