2's complement conversion. Is this right?

[Bob Greschke]

On 2008-04-21 17:06:39 -0600, Bob Greschke <bob at passcal.nmt.edu> said:

> On 2008-04-21 16:51:13 -0600, Bob Greschke <bob at passcal.nmt.edu> said:
> JUST COMPLETELY IGNORE THAT LAST ONE.  What a dope.  Here:
> 
> #! /usr/bin/env python
> 
> from os import system
> from struct import unpack
> 
> print "unpack 1"
> system("date")
> for x in xrange(0, 100000000):
>     Value = unpack(">B", "a")[0]
>     if Value > 0x800000:
>         Value -= 0x1000000
> system("date")
> print
> 
> print "ord 1"
> system("date")
> for x in xrange(0, 100000000):
>     Value = ord("a")
>     if Value > 0x800000:
>         Value -= 0x1000000
> system("date")
> print
> 
> print "unpack 3"
> system("date")
> for x in xrange(0, 100000000):
>     Value1, Value2, Value3 = unpack(">BBB", "abc")
>     Value = (Value1 << 16)+(Value2 << 8)+Value3
>     if Value > 0x800000:
>         Value -= 0x1000000
> system("date")
> print
> 
> print "ord 3"
> system("date")
> for x in xrange(0, 100000000):
>     Value = (ord("a") << 16)+(ord("b") << 8)+ord("c")
>     if Value > 0x800000:
>         Value -= 0x1000000
> system("date")
> 
> 
> Still, the differences between unpack and ord are significant (I just 
> threw in the if's for fun).

I just ran this on my SunBlade 1000 with 2.3.4 and

unpack 1: 7m53s
ord 1: 2m00s
unpack 3: 14m20s
ord 3: 5m30s

timeit looks broken somehow to me.