Skip> I took the original version, tweaked it slightly (probably did
Skip> about the same things as Python #2, I didn't look). For N ==
Skip> 200,000 the time went from 21.94s (user+sys) to 17.22s. Using
Skip> psyco and binding just the advance function on my improved version
Skip> improved that further to 6.48s. I didn't have the patience to run
Skip> larger values of N. Diff appended.
Ah, wait a moment. One more tweak. Make the body class a psyco class.
That improves the runtime to 3.02s. Diff appended.
Skip
% diff -u nbody.py.~1~ nbody.py
--- nbody.py.~1~ 2006-10-06 15:13:31.636675000 -0500
+++ nbody.py 2006-10-06 15:35:36.619976000 -0500
@@ -5,28 +5,31 @@
# contributed by Kevin Carson
import sys
+import psyco
+import psyco.classes
pi = 3.14159265358979323
solar_mass = 4 * pi * pi
days_per_year = 365.24
-class body :
+class body(psyco.classes.psyobj):
pass
def advance(bodies, dt) :
- for i in xrange(len(bodies)) :
+ nbodies = len(bodies)
+ for i in xrange(nbodies) :
b = bodies[i]
- for j in xrange(i + 1, len(bodies)) :
+ for j in xrange(i + 1, nbodies) :
b2 = bodies[j]
dx = b.x - b2.x
dy = b.y - b2.y
dz = b.z - b2.z
- distance = (dx**2 + dy**2 + dz**2)**0.5
-
- b_mass_x_mag = dt * b.mass / distance**3
- b2_mass_x_mag = dt * b2.mass / distance**3
+ dsqr = (dx*dx + dy*dy + dz*dz)
+ dtd3 = dt / dsqr ** 1.5
+ b_mass_x_mag = dtd3 * b.mass
+ b2_mass_x_mag = dtd3 * b2.mass
b.vx -= dx * b2_mass_x_mag
b.vy -= dy * b2_mass_x_mag
@@ -39,6 +42,7 @@
b.x += dt * b.vx
b.y += dt * b.vy
b.z += dt * b.vz
+psyco.bind(advance)
def energy(bodies) :
e = 0.0
--
http://mail.python.org/mailman/listinfo/python-list
