Hello, I am trying to run a simulation in sage as part of my homework. The simulation itself is pretty fast and working fine. The problem starts when i try to run the simulation several times in a loop, then sage becomes incredibly slow in each repeat.

The program I wrote:

```
def poisson(lmu):
var('mu n')
g(mu,n)=(e^-mu * mu^n)/factorial(n)
num=random()
sum=g(lmu,0)
for i in xrange(1000):
if num<sum:
return i-1
else:
sum=sum+g(lmu,i)
```

def galtonwatson(mu,s,gens):
deaths=0
for i in range (gens):
N=1
n=0
while n~~ ~~

`n=n+1 if N==0: deaths=deaths+1 return (deaths/gens).N()`

both of the functions works fine, then telling sage to fill a list of 10 arrays with the values, and checking how much time it took for each repeat:

```
L=np.array([[0,0]for i in range(9)])
for i in xrange (9):
t=time.time()
print i
L[i]= (i,galtonwatson(2,i,100))
print (time.time()-t)
```

Sage output is:

```
0
```

0.000202894210815 1 0.393799066544 2 0.893945932388 3 1.54169392586 4 2.87310600281 5 4.84653711319 6 9.23449707031 7 18.3007540703 8 35.5397469997

It ain't the first time that sage loops becomes slower and slower on the run, and I could'nt understand the reason when searching the net.

Thanks in advanced, David