[Vm-dev] Immediates

Andreas Raab andreas.raab at gmx.de
Fri May 8 00:08:00 UTC 2009

Eliot Miranda wrote:
> I'm told that having 31-bit and opposed to 30-bit SmallIntegers is a bug 
> advantage but I remain to be convinced; VW has always had 30-bit 
> SmallIntegers and seems none the worse for it.

I was going to make a contrary argument, except when I was doing the 
math it didn't go my way ;-) Here is why: Obviously, when having 
computations that can overflow into large ints the performance 
difference is huge (factors of 30-100). However, most algorithms that we 
care about (like crypto) is strictly 32 bit where even with 31 bit 
SmallIntegers we go LargeInt half the time. Consequently the statistical 
difference between 31 and 30 bit for those algorithms should be in the 
range of 50% which, although certainly not insignificant, is nothing 
compared to when you can run the entire algorithm as SmallInteger 

   - Andreas

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