[Date Prev][Date Next][Thread Prev][Thread Next]
- Subject: Saturated Arithmetic (Forked from Swift: overflow raises an error)
- From: Roberto Waltman <techie@...>
- Date: Thu, 12 Jun 2014 23:22:26 -0400
On 06/12/2014 19:48, Tim Hill wrote:
It’s less “ints behave like C” than “ints follow the behavior of the
underlying hardware”, which these days almost always means 2’s
complement with overflow. I’m really not too sure clamping is better
than overflow .. at least with overflow when it happens it’s (usually)
pretty obvious; clamping has greater potential to go undetected.
That is called "Saturated Arithmetic" and is common in DSP processors.
In many situations it is the preferred behavior.
Let's say you are implementing a PID loop to control the speed of an
electric motor. Adding a small positive correction value to a large
positive previous value (that will overflow) will result in:
Saturated Arith will give you still a large positive value (with the
2's overflow will give you a large negative value, reversing the motor
from (close to) full forward speed to (close to) full reverse.
The first error is much more tolerable than the second.