Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!mcsun!hp4nl!utrcu1!kortink
From: kortink@utrcu1.UUCP (Kortink John)
Newsgroups: comp.sys.acorn
Subject: C versus ARM
Message-ID: <806@utrcu1.UUCP>
Date: 23 Feb 91 01:08:51 GMT
Reply-To: kortink@utrcu1.UUCP (Kortink John)
Organization: Utwente, Enschede
Lines: 50

In article <1991Feb18.080958.16120@watdragon.waterloo.edu>
ccplumb@rose.uwaterloo.ca (Colin Plumb) writes :

>kortink@utrcu1.UUCP (Kortink John) wrote:
>>> [...] compiled BASIC is only a tenth the speed of efficiently written
>>> compiled C, and 1/12 that of raw ARM code.
>>
>> Utter nonsense. Good, optimized ARM code is at least twice as fast and
>> short as any C code.
>
>No; the ratio quoted (C is 17% slower) is typical of current compiler
>technology on non-disgusting machines (the Intel i860 is disgusting;
>the ARM is not).  If you can regularly achieve twice the speed of your
>compiler's output, then I suggest that your compiler is not very good.
>
>Some cases can still benefit from human sneakiness, but these are
>usually small.  The ARM is so wonderfully simple, it's hard to hide a
>possibility from a compiler.
>[...]

True, still there is a borderline somewhere along the path to the 'perfect'
code which a smart compiler can't pass, while a human can. It is the problem
content and the programmer's ARM skills that determine how much further the
human will go in the end.

If you need a proof of the 1:2 ratio, look at Impression versus Acorn DTP.
If you need further proof, try writing the machinecode for Translator in C.
I gradually get the impression (no fun intended) that 'C-only' programmers
don't really care about optimization, because they *think* the ratio is
10:12 (so why bother?).

>And in some cases (see Fred Brooks' The Mythical Man-Month), C (or other
>compiled language) can be faster, not because it does X faster than an
>assembler version, but becuase finishing it sooner let the C programmer
>notice that X could be replaced with Y, which is less work.
>[...]

Thats just an example of bad thinking. Look before you leap.

John Kortink

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