Re: CRC in Ada?

[Jim Balter <jqb@netcom.com>]

Robert Dewar wrote:
> 
> TD/DELAB (?) said
> 
> <<It may certainly be less effective, but I cannot think of any
> implementation where it would be a disaster. The C single char IO
> operations are not complicated, and have very little overhead. What
> makes you think otherwise?
> >>
> 
> I'll tell you what. Go measure the relative speed of reading a 1 meg
> file a character at a time, vs using read to read the entire 1 meg at
> a time. Do this measurement on at least six different systems. Come
> back here with the results and we will discuss them!

Instead of being stupid about it, how about just looking at the
getchar macro, which is virtually the same on every single system?
I've done this repeatedly over the last nearly 20 years on many many
systems.  There is a small overhead per byte due to the getchar
macro, which is reduced with good optimizing compilers and good
caching hardware.  For the inner loop of "cat", the getchar cost
predominates.  For anything else, it doesn't.  This is basic
algorithmic analysis, which you can find good references for in your
local library, if you ever bother to head in that direction.

--
<J Q B>