Non-deterministic output

[Laurent Claessens]

> One of us thought it could be set and dictionaries not always yielding
> the same results. I, however, would think that given the exact same
> operations, a set/dictionary would always yield the same results. Am I
> correct? Or could different runs of the same program yield different
> results due to, say, different memory locations?

If you have

d={"a":1,"b":2}
print d.keys()

then there are no way to be deterministic.

What you can do is

d={"a":1,"b":2}
k = d.keys()
k.sort()
print k

This is deterministic.

An other source of non-deterministic behaviour is to rely on the 15th 
decimal of a difficult computation.

I had the following with Sage[1] :

sage: p=plot(x**2,-1,1)
sage: p.get_minmax_data()
{'xmin': -1.0, 'ymin': 3.0448943892610684e-06, 'ymax': 1.0, 'xmax': 1.0}

and in a new Sage shell :

sage: p=plot(x**2,-1,1)
sage: p.get_minmax_data()
{'xmin': -1.0, 'ymin': 1.2545281288559271e-05, 'ymax': 1.0, 'xmax': 1.0}

Hope it helps
Laurent


[1] www.sagemath.org