test_approx.py 文件源码

def test_notracermasses():
    # approx should work with tracer sheets
    # Test that energy is conserved for a self-gravitating disk
    N= 101
    totmass= 1.
    sigma= 1.
    zh= 2.*sigma**2./totmass
    x= numpy.arctanh(2.*numpy.random.uniform(size=N)-1)*zh
    v= numpy.random.normal(size=N)*sigma
    v-= numpy.mean(v) # stabilize
    m= numpy.ones_like(x)/N*(1.+0.1*(2.*numpy.random.uniform(size=N)-1))
    m[N//2:]= 0.
    m*= 2.
    g= wendy.nbody(x,v,m,0.05,approx=True,nleap=1000)
    E= wendy.energy(x,v,m)
    cnt= 0
    while cnt < 100:
        tx,tv= next(g)
        assert numpy.fabs(wendy.energy(tx,tv,m)-E)/E < 10.**-6., "Energy not conserved during approximate N-body integration with some tracer particles"
        cnt+= 1
    return None