Re: ****tability: Harmony between PC and microcontroller

Bart van Ingen Schenau wrote, On 07/05/08 14:05:
> On 6 mei, 19:19, Tomás Ó hÉilidhe <t...@[EMAIL PROTECTED]
> wrote:
> 
>> A better example would be an instant messenger client running on a
>> small handheld device using an LCD display. If the algorithmic code is
>> too slow, then the display will suffer. Using int instead of
>> uint_fast8_t will lead to code which is about 2 to 4 times slower.

Personally I don't see anything wrong with using the fast types when not 
dealing with arrays. With arrays sometimes on some architectures the 
fast type will be slower. Of course, you need to know the range you 
require, but you need to know that anyway to decide if int is large 
enough or if you need long.

> This is where your reasoning starts to break down.
> A small, handheld device is likely to be using an ARM-based processor.
> These processors are nowadays almost universally 32-bitters. (A really
> old ARM processof might be 16 bit).
> Therefore, the difference between using 'int' and 'uint_fast8_t' is
> expected to be zero.

That does not show that uint_fast8_t is wrong.

> The problem with your reasoning is that you try to extrapolate from a
> single experience with one particular embedded system. Your
> extrapolation just does not work.
> I would strongly advise you to gather data-points on about a dozen
> different processors (with as much difference between them as you can)
> before making sweeping recommendations like you do in this thread.

I agree. Now I'll give a reason for *not* using the fast types. 
Sometimes you want to be able to test your code on another platform 
because you have better tools and you want to know that the variable 
ranges will be the same as on your final target even if it means running 
more slowly!

>> I'm talking about ****table performance, not just performance.
> 
> Then tell me, what is the performance of that webbrowser on your PIC?

An algorithm that you might want running on either a small embedded 
processor or a high powered graphics workstation is one to work out the 
optimum brightness/contrast setting for an image based on some 
statistics. I know you might want it on a small processor because I had 
to implement it on one and then later ****t it to another smaller 
processor (in both cases HW collected the statistics, I only had to 
process them in real time), and the use on a high powered graphics 
workstation should be obvious. The same can apply to some other image 
processing algorithms, so it does happen.
-- 
Flash Gordon