No built-in swap function?

[Josiah Carlson]

> The xorswap function is not much use for anything other than numbers,
> however, I would have expected a psyco'ed xorSwap to much faster than
> the alternatives!

You are testing function calling overhead.  Try the below...

import time

def tupleswap(a,b):
     t = time.time()
     for i in xrange(100000):
         a,b=b,a;a,b=b,a;a,b=b,a;a,b=b,a;a,b=b,a;
         a,b=b,a;a,b=b,a;a,b=b,a;a,b=b,a;a,b=b,a;
     print "1 million tuple swaps in", time.time()-t, "seconds."

def tempswap(a,b):
     s = time.time()
     for i in xrange(100000):
         t=a;a=b;b=a;t=a;a=b;b=a;t=a;a=b;b=a;t=a;a=b;b=a;t=a;a=b;b=a;
         t=a;a=b;b=a;t=a;a=b;b=a;t=a;a=b;b=a;t=a;a=b;b=a;t=a;a=b;b=a;
     print "1 million temp swaps in", time.time()-s, "seconds."

def xorswap(a,b):
     t = time.time()
     for i in xrange(100000):
         a^=b;b^=a;a^=b;a^=b;b^=a;a^=b;a^=b;b^=a;a^=b;a^=b;b^=a;a^=b;
         a^=b;b^=a;a^=b;a^=b;b^=a;a^=b;a^=b;b^=a;a^=b;a^=b;b^=a;a^=b;
         a^=b;b^=a;a^=b;a^=b;b^=a;a^=b;
     print "1 million xor swaps in", time.time()-t, "seconds."

a = 2**30-1
b = 2**16-1
tupleswap(a,b)
tempswap(a,b)
xorswap(a,b)

Without Psyco (on a celeron 400):
1 million tuple swaps in 1.10899996758 seconds.
1 million temp swaps in 0.703000068665 seconds.
1 million xor swaps in 2.14099979401 seconds.

With Psyco (on a celeron 400):
1 million tuple swaps in 0.0 seconds.
1 million temp swaps in 0.0 seconds.
1 million xor swaps in 0.0 seconds.

Having 100 times as many loops for the Psyco run (xrange(10000000))...
1 million tuple swaps in 0.125 seconds.
1 million temp swaps in 0.125 seconds.
1 million xor swaps in 1.04699993134 seconds.


Looks like a big win for Psyco to me.

  - Josiah